1994 Chevy C1500 5.7 bogs/backfires when I give it gas.

560

Asked by Oct 10, 2013 at 01:26 PM about the 1994 Chevrolet C/K 1500 Silverado Standard Cab Stepside SB 4WD

Question type: Maintenance & Repair

My truck bogs down (and tries to die) when I give it gas to accelerate off of a stop. There
is often a backfire or two when this happens. Pumping the gas does not help. I basically
have to crawl through any intersection until it picks up a bit of speed from idle. The truck
idles smoothly, and it runs fine once it's above about 5-10mph or so. If moving at a
steady speed, and I give the truck gas to accelerate, it hesitates and backfires before
picking up the speed. It may be worth mentioning that this problem doesn't happen if I rev
the engine in park or neutral, unless I really gun it, in which case it's a quick backfire and
back to business.

This is inconsistent; sometimes the truck runs like a champ, but most of the time it's
trying to leave me stranded in busy city intersections. This has been happening for about
3 months (yes, I know I should've fixed it months ago; times are particularly tough)

I've changed the inline fuel filter, changed the plugs/cap/rotor, checked the sparkplug
wires, and run a fuel system cleaner through it. I unfortunately don't have a fuel pressure
gauge.

I doubt it's relevant information, but the truck just passed smog check a couple days ago
with no issue, although I didn't see the kid even glance towards EGR/PCV valves.

Any help is greatly appreciated. I can't afford a mechanic, and I'm just praying it's not the
fuel pump.

59 Answers

560

I failed to mention that the Check Engine light is NOT on.

56 of 56 people found this helpful.
290

I had the same issue.. It was particularly a little worse until I canted my Cam Shaft Position sensor located inside the distributor cap, and also changed the connecter wires to the crankshaft position sensor located at the front bottom of the engine by the fan kinda. It still does it a little but not as bad as it did so I would start there to improve it some.

29 of 29 people found this helpful.
410

Same thing here. Did you ever find out what was wrong with it? I've changed/ replaced cap, rotor, wires, plugs, crankshaft position sensor, cam position sensor, MAF, IAT, TPS, coil, fuel filter, oil and filter. nothing seems to work. i've checked for vaccum leak, fuel pressure, fuses, shorts, etc.. Im still fighting this battle so if anyone has any tips I'd greatly appreciate it.

37 of 37 people found this helpful.
410

Have you found out the problem with your truck I have a 1994 chevy c1500 5.7, it mostly backfires when driving on the highway or interstate but once it starts it continues to do it with in town driving to. A lot of the time I have to shut it off and start it back up to get it to quit to get it to quit but ithe usually only stops it for a few minutes. I would also greatly appreciate any tips.

42 of 42 people found this helpful.
420

My 94 Chevy Silverado was also sputtering, backfiring, missing etc... I changed the fuel filter to no avail, tried several things to get it to run smooth but nothing helped' until a friend of mine who used to have his own shop told me about a memo he had received years ago dealing with this identical problem. here's what worked for me! I unplugged the idle air control from the left side of the carb (as you are facing it) took a large wrench and removed the idle air control from the carb, and sprayed it down with carb cleaner. then I sprayed the fitting on the carb where I removed the idle air control unit from and sprayed that throughly also. then I sprayed the carb itself. once this was done i let it dry for a few minutes, re assembled everything and tried to start my truck. starting the truck was not easy because of the carb cleaner. it took a minute to start, but once it did it ran like new!!! it has been running well ever since. I hope this works for you as well as it did for me.

42 of 42 people found this helpful.
190

I have a 1994 chevy 1500 , 5.7 . I took off the transmission to work on the rear main seal . Put the transmission back on and the truck wouldn't start . I than checked the battery got a new one . Than the the starter is new the rotor and cap are new the control madule the iac is new fuel filter in line is new plugs.I can get it to start but only stays running for maybe a minute or two

20 of 20 people found this helpful.
590

To the fella that had his friend with memo, by God when i tell u we have had nothing but trouble with this 94 Chevy since we bought it last year for 3200 replaced so many things on it, it's doing same thing it did last year when we got it out, they said we had water in gas that went through the injectors, We replaced I'm n plugs n have drop gas tank n cleaned it out, it's backfiring and carb has flames, We sprayed it and that was result but haven't removed the new icv n sprayed it

10 of 10 people found this helpful.
40

thrudel controll value

4 of 4 people found this helpful.
140

i have a 1997 chevy 1500 and i have replaced the camshaft sensor and the icm it fires up and back fires then just turns over any ideas would be greatly helpful

14 of 14 people found this helpful.
80

Ideal air control valve, or throttle position censor or both. Get a paper clip and bend it until u have 2 points next to each other about 1/8 apart. Turn your key to on position (Don't start it) just on position. Stick the paper clip into your obd1 at the top right two inserts then count the number f times your check engine light blinks. You'll have sets of 2. Like 1 blink then pause then 2 blinks Your obd1 is located under your steering column

8 of 8 people found this helpful.
60

Hey guys I was having the exact same problem with my 1998 silverado 5.7 liter. I noticed gas some time ago right where the fuel rails go into the intake,and on the right side of the rails there is a cover with wires under it and they were eaten up by the gas.I had the same symptoms as everyone. Used liquid tape to recover exposed wires just to find out the gas is coming from under the wires. Off to the shop we go.I hope this helps.someone

6 of 6 people found this helpful.
330

i dont understand what up with my truck either its a 1994 c 1500 and when i start it it acts like it wants to dye and when i reverse it dyes and then when i try to go it trying to dye and back fires and when i hit the gas it tries to dye and wont go. i have replaced the spark plugs and wires and fuel filter and fuel pump and throttey sensor and still have the proble. the worse time is if its cold or been satting for awhile then it acts up. if anyone can help me find the problem please let me know.

27 of 27 people found this helpful.

It might that the transmission is going out

330

I replaced the transmission already

2 of 2 people found this helpful.

Try a timeing light check the timeing

220

Holy carp my 94 cheyenne k 1500 5sod 5.7 is doing the exact same thing everyone described but it just started last week. I replace entire fuel pump sending unit few months ago so its new. But just blew clutch fork out last week n pulled tranny n replaced it now I'm having same problems everyone's describing sometimes stslls when idling and 2nd and 393rd hear around 2500-3000 rpm starts dying out and backfires then picks back up. Don't have the $ to just start replacing everything. Just put cap n rotor n still doing it. Going to replace wires n plugs on payday. Any help would b greatly appreciated and can't afford mechanic so I'm doing it myself and need the truck for work.

22 of 22 people found this helpful.
70

have a 87 p3500 stepvan everytime i hit a bump going down the highway it tries to stall then sometimes it will pick back up sometimes it won't but when it ttys to stall it often backfires no plugs and wires checked all electric any idea what this could be?

5 of 5 people found this helpful.
195

My 1958 Chevy 283 Power Pack has been backfiring, stalling and hesitating at the wrong times. I have been told to rebuild or replace the giant four barrel carb and that will settle it down. It's never been cleaned.

2 of 2 people found this helpful.
70

i was going to try to get a new carb but wasn't for sure that could even be a issue everyone kept saying electrical but i found no loose wires or anything at this point its a gamble sinking too much money into a bunch of things that won't fix the problem almost worth getting a new motor

2 of 2 people found this helpful.
330

i cant afford a new motor or to a place to have it looked at either. so i guess ill either keep buying parts or just junk it but i need it for work so i don't know what to do. if anyone can help me i would love it but if not ill keep buying parts till i find out whats wrong with it and hope it can take me back and forth to work till i find out whats up.

5 of 5 people found this helpful.
110

my truck dose the same but bogs when im driving no at a dead stop and when it bogs it dosnt come back untill my truck is fully turned off for at least 5 min. possible its a fuel filter / pump but not 100 percent

11 of 11 people found this helpful.
170

My 1993 5.7L TBI engine would bog down when climbing any small hill and the fuel economy was horrible. I used the symptoms and troubleshooting from the above comments and solved my problem. Thank you very much. Here is my solution. Sorry for the long story, but all is helpful in the long run. I removed my ignition control module and took it up to the orange auto parts store to purchase a new one, but the helpful parts person told me, before I purchase a new one, to go to another orange store and have it tested since they misplaced their instruction manual for their module tester. Instead, I went to the green auto parts store across the street and had the module tested. The two counter persons were not properly trained on how to properly operate their module tester but hooked it up from their instruction manual "without grounding it" and my module repeatedly failed all of the tests. I went back to the orange store to again purchase a new ignition control module but a different counter person found their instruction manual and tested it "while grounding the case." The module repeatedly passes all tests. I then recognized the differences in the grounding and then recognized small burn traces on the back if the module where it had appeared to be arching. I then suspected that the module was not properly grounded in my vehicle since the hold down screws were very rusty and the heat sink grease was gone between the two metal surfaces. I purchases some new heat sink grease at Radio Shack and went home. I uses a small wire brush to clean off the rusted screws and mounting surfaces. Applied new heat sink grease and reinstalled. Wiggle the module back and forth for a minute to properly distribute the heat sink grease. I backed off the screws several times to get the serrated screw washers to make a good grounding bond and put the cap back together. All of my engine bogging issues are gone. I can now rocket up a hill. Lessons learned: 1) Make sure the parts service persons are competent in their job. 2) Radio Shack has heat sink grease when the auto parts stores do not. 3) Make sure the ignition control module mounting screws are free of rust and the module is properly grounded. 4) Wear latex gloves when handling heat sink grease. It is contagious like a disease and gets everywhere you lease expect it.

17 of 17 people found this helpful.
130

Hey guys I have been having the same surging issue from dead stop for months.. I just allow for the slow acceleration time as the truck is old and mechanics are expensive.. But the last week I was traveling and the truck just shut off no burp chug or chatter.. Just went to give it has and nothing there.. So after trying to trailer it home unfortunately my winch wasn't strong enough to pull the truck up.. I replaced the ICM on the side of the road and it fired right up.. But I still have the surging/backfire from dead stop. Any other suggestions? I'm purity sure I have a throttle body and 2 injectors.. Would the idle sensor still be present?

13 of 13 people found this helpful.
140

I have a 98 1500 4x4 5.7 vortex. Was able to start with a little starting fluid to move around but now no start. It has new fuel pump. When it was starting it would not want to go when I gave it gas, unless I barley press the gas. Never backfired. Please help!! Wrecked my car so now need this as a daily.

14 of 14 people found this helpful.
90

I have a 1993 Suburban K2500 with a 454 c.i.d. that has a rough idle, and will bog down on acceleration. When I'm at freeway speeds, it will surge and backfire. I have tried all the fixes above including; TPS, MAP, IAC, O2, fuel filter, cap, rotor, plugs, wires, throttle body base gasket, computer, promand the list goes on and on. I have replaced the distributor about 3 months before this problem reared it's ugly head. I have re- grounded the entire engine with several new ground straps and replaced wiring to the knock sensor, the O2 sensor, and the coolant temp sensor due to age and oil contamination. I have also replaced both positive and negative cables and ran a new ground to the PCM. Any thoughts???

9 of 9 people found this helpful.
110

My 96 c2500, 350 tbi, has been spuddering, idling really rough, backfiring, amd plain out dying in town. Sounds like plugs but its not, distributor maybe? Timing? No engine light either So i was just tinkering with the truck, and the wire under the the glove compartment, its brown and black, (you disconnect it before you do set the cap for your timing) i unplugged it and the engine light came on, but the truck instantly started working way better. It dont make much sense to me and i am not sure if its really safe to run that way. It seams like it might be smoking a little maybe? Any thoughts or ideas?

11 of 11 people found this helpful.
70

most of the folks here with these problems mention a transmission replacement, you have a constant hot wire that runs down and around the stock exhaust manifold and through a heat shield and back to firewall. I also swapped tranny out of mine, (for another truck) and then back in (to drive this truck again) and forgot to bolt the heat shield back via the bell housing bolts. This allowed the always hot wire to ground out on the exhaust and the truck would sometimes die, always backfire, and it usually happened when I hit a bump. I disconnected the wire, pulled it through, taped the exposed wire, ran it along the inner fenderwell and up by the ac drier and back to it's original location without getting anywhere close to the exhaust. Also, there are other backfiring issues, that sound like this is not the problem... these trucks' have distributor issues, a new distributor will likely fix your problem. A coolant temp sensor will make you run rich, the pigtail wiring harness always gets internally broken on these due to the way the engine rocks under load, try to wiggle yours while running to see if the problem fixes... also the TBI injectors have their wires running through a rubber gromet and that over time can wear out and the wire grounds to the air cleaner assembly. if you gun it and it picks up then immediately loses power and check engine light comes on it's your knock sensor most likely, or the connector is loose. and one very important thing to remember, if anything is not properly grounded, or not getting proper power, it will not work, and when sensors don't work on a computerized engine you will have big problems!

2 of 2 people found this helpful.
70

bogey, if it's smoking black it's running rich, you'll foul out your plugs running it like that, the knock sensor and electronic spark control module are responsible for adjusting your timing. the ESC module sits under the air intake side of the air cleaner and you should check the wires running to it, wiggle test, and also check that there are no vacuum leaks there and that the vac line is hooked up. your knock sensor is on the bottom of the block, cut your wheel all the way to the left and look behind the plastic fenderskirt. give the knock sensor a wiggle test too. now assuming these two are working properly, the distributor takes the signal, and adjusts timing accordingly, these trucks are known to have distributor issues after 150k or so autozone has them for around 60-70 stock replacement, you'll then disconnect the wire you mentioned to adjust your timing to get the Base timing for your engine. Also, you didn't mention if it did, but an exhaust manifold leak, or noisy lifters even could trigger the knock sensor to retard timing prematurely. have seen guys use knock sensors from 454 to cure this problem because they have a higher tolerance for noise before retarding

3 of 3 people found this helpful.
10

try mass air flow with all your back fireing and sputtering

1 of 1 people found this helpful.
30

i had this problem also and replaced most of my sensors, with further research i found fuel pump has a strainer at its inlets without hesitation i dropped fuel tank and removed pump. i discovered the sock was covered in debris, went to local autozone and purchased one for 4bucks. replaced it and reinstalled tank. the truck would start and idle fine just under loan it would bogg and try to kill its self. after replacing strainer i lightly accelerated and noticed the truck has sensitive acceleration response. after replacing all sensors and finding problem my 1989 Chevy Suburban (350-TBI-5.7) runs like its right off the lot!!!

3 of 3 people found this helpful.

I have a 1992 Chevy Silverado extended cab 4 wheel drive automaticit'll pick up gas then just bog down cant give no gass or it dies can some tell what it is bec I spent over $1009 allredy

70

I could give you a long list of things to check, but you could get a better answer by listing things you've already done. Air/Fuel/Spark that's all you need for an engine to run. check your air filter for restrictions, check your coil, check your fuel pressure. could be a timing issue, fuel issue, cat converter, etc.. If you could be more specific it'll likely be easier to pinpoint your problem.

2 of 2 people found this helpful.
10

I rebiuld my pick up chevy s10 to race and its doint that to it bog out and dies i tryed looking for a mecanic but they say its a spark plug but its bran new i tryed to race a corvette with it and the motor. Is so strong that when it bog out and i try to accelarate it dosent accelarate but with that motor the way its acting now i broke to transmission and i beed help finding that problem to but there aint nody out there that know i have a race in like a month from nowto race a camarro but it keep bogging out help me as soon as posible

1 of 1 people found this helpful.
30

I've had all these same problems with my 92 Chevy 1500 and replaced fuel pump, filter, egr vaulve, distributer cap and roter, the coil wire and coil itself. Didn't do nothing. Then I found out one of my injectors weren't spraying so I was only running on 4 cylinders. So I rebuilt it and it was running like a champ for a good month and now it's doing it again. But only when my trucks been running for a while. Give it gas it sputters and kinda back fires. But when I get up to speed it runs fine until I accelerate.

3 of 3 people found this helpful.
20

my 1996 chevy c1500 is doing the same thing. mine sputters when i try to accelerate then it decides that it wants to go after about 5-10 seconds of sitting there sputtering and backfiring. The engine only has 85000 miles on it. it is a 5.7 liter 350 vortec. it already has a new maf sensor that i installed about 6 months ago. Ive checked all the wires, still have to check all fuses though

2 of 2 people found this helpful.
10

i had all of those problems its the throttle sensor on the outside of the air intake opposite to where the throttle cable connects. or i just floor it and over time the problem went away

10

i have a 93 c3500 with a 350 tbi

1 of 1 people found this helpful.

The only guy who fixed the problem emptied the tank. I think it is water in the fuel. Under a load at slow speeds the water and fuel is burned in the cylinder creating a backfire, as the steam expands. The stall is from an incomplete fire because the water put it out. Since these vehicles were born before e85 fuel, adding ethyl alcohol could cause the rubber/plastic fuel lines to corrode and fail so be careful when adding additives. best advice take it to a professional and have the tank dropped.

25

There is a transmission module located on the passenger side of the transmission. This module opens and closed via a vacuum line. it is in the shape of a curve or an "S". You will need a cutter to cut thru original clamps. Make sure you see this rubber hose. Replace the hose that is where you will have a vacuum leak. Replace hose with new one and don't forget to buy two new clamps. This should resolve your issue of sluggish running backfire. I recommend you all try this first. IT take all of about 15 minutes to replace once you have all the items ready to reinstall.

1 of 1 people found this helpful.
30

I have 96 chevy 1500 with 4.3 manual trans and I have changed distributor cap/button/wires/plugs camshaft sensor coil and little black box on coil and truck idles great but when giving it has or cruising at 1500 and up its backfiring and sputtering and now my gas gauge is acting weird does anybody know what's going on

2 of 2 people found this helpful.
195

I agree!

Me too except my service engine soon blinks fast when I'm driving it. I have changed the rotar, cap, spark plugs, and fuel filter but it seems to run better on a dry sunny day than a cold or rainy day. Any suggestions

20

I have a 1994 chevy 350 5.7, back a few months ago I was going up hill and started to stall so I floored it and then I had engine ping got back home moved my timing little back the pickup ran awesome til now. There's no engine ping, it starts up fine, but soon as it warms up it starts to choke out at a idle sputters and backfires above 2500 rpms, just replaced the IACV it had no good affect. Cap, rotor, plugs, wires all have about few thousand miles on them also the egr valve, map sensor where also replaced. I got good fuel pressure, new fuel filter and now I'm trying to figure out what is this time. Any ideas are solutions will be very helpful

1 of 1 people found this helpful.
20

also there's no service engine light

20

okay figured it out bad distributor replaced it with a new runs like a champ now I hope this helps someone

1 of 1 people found this helpful.
20

!992 Chevrolet 5.7l Backing firing thru tbi,poor millage,hesitation on acceleration. Found throttle position sensor intermittent contact.replaced runs great now.

2 of 2 people found this helpful.
30

I have a 94 k1 500 with 5.7 350 I have replaced pump filter distributor plugs wires cap button iac ips map tps computer pcm throttle body tps egr valve hose sensor that goes to egr don't know what it's called o2 sensor and it runs fine in park but when in gear only sluggish when giving a lot of gas on take off or when I'm in a high gear at low speed pops through tbi I'm lost never done so much to truck and not fixed

3 of 3 people found this helpful.
20

I am having the same issues but the check engine light is on. Rotor, cap, wires, and plugs have been replace. Rebuilt the TBI cleaned the IACV and the TPS. Still doing the same thing. If anybody has anything new that would be much appreciated! thanks for the advice.

2 of 2 people found this helpful.

My 95 c2500 was doing the same thing. Id tried new fuel filter checked all plugs and wires. Then someone told me the map sesner could be bad and be forcing the injectors to dump fuel. So far its worked. Also cleaned my throttle body and aired out all gas in the throttle body. Check to make sure its not flooded and your injectors arent bad. Lots of digging but it seems nobody has the answer to this problem

98 Chevy C Series Auto with 4.3 L. Following this thread. So far I've changed wires, plugs, fuel filter, air filter, oil filter, oil, fuel pump, spider injector and all poppets, catalytic converter, cleaned muffler. I see that distributor is a possible problem, may change that. I also noted the sensors (Throttle, IAC, Map, etc.) I will post a solution if I find it. May God help me find it. I have 3 days then I must be on a job with it. If you read this and it stands out taking in account what I have already changed, then let me know. Thanks.

20

I just bought a 94 K1500 (133k) with these driveability problems. Would really bog down, esp when cold and trying to go uphill... but felt weak under any acceleration. Previous owner did new distributor, MAP, plugs, IAC... still ran like crap! I repl'd temp sensor. The game changer was the EGR solenoid, hardly visible, rarely mentioned. Immediately started, had power on takeoff. ACDelco part, $25 2 day delivery via Am-Prime.

Bro, I feel ya. '94 K1500 Suburban with 360K mi. Been doing well with normal "old age" issues: trans rebuild, cooling system, charging system, and then the shudders happened. The engine starts and idles with no problem. At about 1500 - 1700 rpm under power, the engine bounces like crazy. I add more gas and as I reach 75 mph the engine miss is bearable. After work I ready for the 1.5 hr commute home- the engine runs smoothly until I hit 45 mph and then the bronco ride starts anew. The check engine light is sometimes on and sometimes off. The code is 32- EGR valve I understand. So far I have replaced the EGR valve, EGR control switch, TPS, Dist cap & rotor, and zip-tied vacuum fittings. I will keep you updated

20

Jack, How long have you had your K1500? Good that you accept that some work is expected on an old truck... but the frustration is understood. I was too optimistic. The EGR solenoid was not the end of my trouble, but it helped. I replaced O2 sensor and fuel filter, but get a code-44 (lean exhaust). I tested fuel evap canister and purge valve, but they were OK. Been doing "Techron therapy" (the weak formula), but am thinking/hoping that injectors might be the issue. They're a relatively cheap fix. I sure read a lot about fuel pump, pressure issues, dirty sock filter, and replacing 42 gal tank... don't like the sound of any of that. You can compare the color of two plugs on opposite sides of the engine (#3 vs #4), if different, may indicate a bad injector on one side, thus causing roughness, etc. That is actually good news... better than doing anything else to the fuel system! A low end shudder, hesitation, etc. is unfortunate, because a truck engine runs mostly at low rpm.

1 of 1 people found this helpful.

The IAC was mentioned earlier. I pulled it and cleaned it. Idle a little high at first then it settled to around 200. Overall, no change.

I bought my burb new in 94. It has been through 4 kids and all of their swim meets, ski trips, cross country races, tennis tournaments, basketball and softball games, campouts, trips to the city and to the mountains. It's been a workhorse and now it's my adventure race, golf outing, backcountry fishing, backpacking, and just plain get outa town rig and I want to keep her going. I am thinking of a new crate 350. It's going to cost about $6K. I know that I will never get that back if I sell, but who's looking to sell.

20

Wow. So you REALLY know its history! Sounds like a life well-lived! The truck also :) My '94 Sub was owned by a guy for 18 yrs, but he had so many vehicles, I doubt if mine was maintained in detail. You would know, then, how old your injectors are. These TBI 350s are very sensitive to vacuum leaks... which can show up in weird places, including intake manifold, base of TBI, etc, not just old hoses. Also, there is much discussion about fuel pressure (at various points), wimpy fuel pumps, and dirty fuel tanks. A new crate engine sounds great, BUT, you'd be in awfully deep if tranny, diffs, etc, started acting up. There is some good diagnostic advice @ tbichips.com and also some info on these motors, if you are going to replace it. Ours are not as upgradeable as some other years. Our valves and exhaust are also pretty limiting. It'd be useful for you to know what your compression #'s are, as far as decision making... Good luck and continued adventures.

1 of 1 people found this helpful.
10

OBD1 chevy 5.7 TBI - This issue you all have with the backfire through the carb when accelerating from stop.One thing you have to do is very all emission control sensors are operating correctly. Buying a new one without verification is just a waste. If you don't know how to test, Take it to a mechanic. Unfortunately a lot of the old school mechanics just don't understand the electronics. If everyone agrees that the main cause is a lean fuel condition then you need to look at all the scenarios that cause that condition. Here is my list: 1) Weak fuel pump clogged filter anything that hampers the delivery of fuel. This one is easy to eliminate, If the engine runs perfect before going into closed loop it's not the fuel delivery. 2) Problem starts after it goes into closed loop. Things to do, a) Check voltage at fuel pump and compare to battery voltage. The ECM compensates a low battery voltage by increasing fuel flow. If the battery voltage is good but there is low voltage at the fuel pump then it may be causing your lean condition. Check and clean all your grounds. Those cheesy connectors from the factory loose their conductive properties. When they get hot the resistance goes up naturally, but bad connectors will throw a large resistance in the circuit that screws with the electronics. 3) Your engine is worn out, valves not seating compression is low, etc. Compression and leakdown test will help pinpointing that problem. 4)Advance the timing 10 to 12 degrees, see how it runs. If it runs great the the problem is not fuel delivery per say but it probably can be seen in the fuel trim numbers. The 2500 series snap-on scanners are a good tool for this stuff. 5)Also, vacuum leaks can cause this issue, with the scanner your long term fuel trim decreases rapidly, as it does the engine runs leaner and leaner. Really bad because detonation (pinging ) will crack your compression rings in short time. Don't think you DONT have a vacuum leak with a vacuum gauge. ECM will compensate by advancing the timing so it idles with very little problem. Remember the problem occurs under heavy load. Some intake leaks can be difficult to find. If your engine has ever overheated, 9 out of 10 times you will find the TBI / Intake leaks around the base of TBI. Around the TBI mounting bolts. The port and head planes are no longer in sync. I made a plate that bolted to the intake manifold where the TBI mounts. Remove the valve covers and loosened all the intake valve rocker arms. Oh I forgot to mention I threaded a fitting with a schrader valve in the plate so that I could pressurize the intake. Basically a reverse leak down test. The leaks were around the intake where the TBI sits. Mill the mounting plane to make it true, no leaks. 4) O2 sensor slow or off just enough to cause ECM to trim fuel back. 5) The first generation, OBD1 vehicles as simple as they are, are very difficult to maintain in proper running condition. OBD2 is more forgiving with much less mystery. Pulling codes and buying parts is what they want you to do. Don't fall into the trap. Most of the problems with my 94 chevy was sensor wiring. Of course it took a long time to find the backfire problem. Constant lean condition causes the compression chamber to operate at extreme temperatures. Wore the rings out by 150000. Just finished a complete overhaul, it was on the bucket list, rings haven't seated completely with 75 miles on the engine but I can tell that things are lookin up. If it wasn't for the custom work I did previously I probably would have sold it to the wreaking yard years ago. Good luck

1 of 1 people found this helpful.

So I took the burb on a road trip up into the mountains. First, I replaced the ICM. One more thing to check off of the list. I did not notice much of any improvement in performance. Another thing that was not mentioned is that connections become very brittle with age. I destroyed the connector for the ICM to the distributor pick-up module. Something more to replace. Anyway, as I was decending a very long (5 mile) steep stretch of road I dropped the transmission into 2nd gear in order to save my brakes. The engine did a very good job holding my speed down and it did not backfire at all. Might this be an indication that there are no issues with the valves? That was 300 miles ago. The baffles in the muffler had begun to rattle about before the trip, so I replaced it last weekend. Now the truck is a bit quieter, but it still stutters at low rpms under power. I am still getting the 32 OBD1 code. While I am pondering my next move, I will do a break job.

10

How's it going fellas It appears that everyone has attempted to fix their 1988- 1999 Chevy Silverado Makes complete sense with several answers. I too have the same problem with my 1994 Chevy Silverado 350 5.7. My Truck ran as if it was like a new truck, It passed the California State Smog Test but for the last several months when I accelerate my Truck if begins to badly bog, But there's one common problem that no one has checked. EGR, You need to check too see if the passive line is clogged with carbon, if it's clogged it will more likely cause the Truck to bog. Another words, the EGR operates the same as vaccum, if its clogged it won't function. I'll work on my truck 9/16/2017 will keep you posted. I may take pictures to show you a clogged passive line / channel. Thanks Dennis California

1 of 1 people found this helpful.

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