1992 Chevy 1500 running rough and strange rapping noise in exhaust.

25

Asked by Jul 12, 2015 at 05:08 PM about the 1992 Chevrolet C/K 1500 Scottsdale Extended Cab LB

Question type: Maintenance & Repair

I have a 1992 Chevy Pickup says W/T 1500 on the side, it's rear wheel drive with a 6
cylinder motor.I am having an issue currently with it chugging and choking when the
truck is in drive while holding down the brake.  Also when you accelerate it makes a
loud rattling, almost like a rod knocking horribly but it is coming from the exhaust, like
a loud rapping sound.  when the truck is idling in park, there is a kind of "whup, whup,
whup" that you can hear in the exhaust.  Almost sounds like it would have some power
behind it lol.  Now I jacked up the rear and had the tires off the ground and stepped on
the gas to see if I could tell where the rattling sound was coming from but it was not
doing it.  it only seems to do it when the vehicle is on the ground going down the road.  
But it did choke and sputter when the brake was applied while it was jacked up.It's
definitely not an engine knock, but I don;t have any idea what it would be.  Any
suggestions on where to start looking would be helpful.  Oh, and the check engine light
in the truck has not come on for this issue.

44 Answers

20,825

humm ..timing chain? brake vacuum leak...

25

I didn't notice any vacuum leaks anywhere, I will look closer again. If it were something with the timing chain, wouldn't it run crappy all the time?

17,840

You have a baffle that has come loose in your muffler.

7,840

Suspect misfire too, as well as loose parts in the exhaust. At the gm garage, the back counter can likely give the basic group of goodies you may need to the front counterman to sell to you. Vacuum leaking at components can be verified by pinching the supply going away from its source at the intake. Misfires leave evidence behind on the spark plugs. Failed ignition parts leave evidence of burning and ashes or white dots on the wires where they may arc. A/C delco parts fit, last longest, run right longer saving you money.

25

Well... As for the misfire, I changed all the plugs and wires before I posted but I went and checked for spark on all of them and it's all good for spark. Now, as of today, when I was driving to work, about halfway there the strange rapping sound that I had suddenly stopped. I got up to the stop sign and when I applied the brake to stop and was sitting there it was chugging and lurching bad and I was sitting in a cloud of white smoke. I made it to work but I am now blowing white smoke out of the exhaust. I let it cool down while at work because it was definitely bubbling some when i got there, and I checked the oil because I thought maybe I had a blown head gasket, but the oil is fine, does not appear to be any anti freeze in it. I did have to put about half a gallon of water in the radiator as it was low, and I made it home that way without anything seemingly getting worse. I can tell you that when you start it, it feels like there is something binding it from turning over and then it will finally go, was that weird rapping sound maybe the water pump bearing going out? How would I get anti freeze in the exhaust and not in the oil?

1 out of 1 people think this is helpful.
12,535

At first I thought it was a clogged catalytic converter. Then as I read further it sounds like a head gasket is gone bonkers and pumping radiator liquid into a cylinder and it is causing your cat to act up. Pull the plugs and see if there is any fowling going on. If you can or have time for someone to do a pressure test on all cylinders, you may find either a blown head gasket or a cracked head. If you oil is starting to look milky in color, it is a head gasket leaking or cracked head.

25

Yeah, I can check the plugs, but there is no catalytic converter on the vehicle, and the oil looks like normal oil, not milky at all.

17,840

Because you do not have a blown head gasket you have a crack in one of the cylinder heads dropping anti freeze into the cylinder the reason that it is not in your oil is because it is being burnt off with the gas that's why you have the white smoke coming out of exhaust.

17,840

Let me break it down to you like this. When a head gasket blows it drops a large amount of anti freeze into cylinder that is why anti freeze gets into the oil it seeps past the piston ring and into the oil now a cracked cylinder head is dripping anti freeze into the cylinder and is being burnt off with the gas and when the vehicle is turned off it stops leaking because the water pump has stopped pumping that is why no anti freeze in oil.

7,840

He is making antfr. steam, hearing hydrodynamic bump bump of water in the cylinder(s) His former plug(s) may be steam cleaned but turning green in appearance I would think. and his misfire contiues even though spark was verified because he no longer has an air fuel mixture but now has antfr./ fuel/ air. He can pressure test cooling syst, remove plugs, let sit, then crank engine to watch the spray and decide for himself where his leak(s) or crack(s) and how many places.

7,840

Whether to pull the head or heads and know which cylinder or cylinders to find the breach or the crack. good to know before teardown, or even if its the intake leaking into the head then into the cylinder. GM V6 is an intake gasket leaker in many years and vehicles, the cams have been reported worn from using just a few ounces between oil changes, but it trickles enough to displace the lube and wear lobes. depending on the severity, our engine guys may opt for replacement rather than partial repair, after post mortem. depends upon coverage, cost, decisions of management. If you fix your own, you might decide to list all the affected parts, make cost analysis, LABOR? updates? and whether you are keeping it for enough years.

7,840

Individual cylinder leakdown, of course can prove and be measured but finding the intake only scenaro can be just a matter of intake removal for inspection. stop leaks are dumb, do not waste your everything, there will be an updated gasket set and procedure offered by TSB bulletin. There always seems to be...

25

Hey guys, thank you for all of your answers and suggestions so far. You have been pointing me in the right direction and little by little I think we might be getting there. I changed the water pump today and it must really be working now because it blows alot of smoke now and leaves a puddle on the ground under the tailpipe. The smoke smells like gas and antifreeze which I assume it should if it's all mixing together in the cylinder. I did have a bottle of that coolant stop leak that was supposed to fix head gasket leaks, cylinder head cracks and leaks etc lying around so I gave it a try. Didn't make any difference at all ao i assume the leak, crack, or w/e else the problem might be is too big to be sealed. I will stat with what DannyI said and pull all the plugs and crack it over and see what sprays out of where to know at least what side to look on (hope it's just one side) If I remove the intake, will I be able to tell if that is the problem? Will it show some sort of sign if it was the gasket leaking?

1 out of 1 people think this is helpful.
7,840

Look at the 4th 10th, 11th, and 12th posts again for this page. You must pressure the system, pull the plugs, and crank it over. that tells you what hole or holes (cylinder). You ask GM for the right intake gasket set. discuss whether it comes from the bulletin or has new procedures to follow. During engine testing you can leakdown or compression test with the rad cap off and after some tries on each cylinder, you could, likely see bubbling from the rad. if that's true, you trapped compressed air and it found a path out thru the coolant. that means head for the cyl you tested. They all leak at the intake, with severity you can see that when you take the intake off and the gasket off, the streaks of coolant wash towards the cam, if that has ruined your cam, you get to really look into engine repair/ replace.

7,840

Knowing the damage a little coolant can do, and not found for several oil changes to be really losing coolant, the few ounces it does use can show by needing coolant added to the reservoir, an inch or so in the bottle reservoir. That coolant has entered by way of the intake most likely, over that time and those miles the coolant has taken the place of oil in some favorite spots and begun destruction. HOW BAD ? thats what you want to know. But you may be able to do any number of partial repairs on your own. I just know with the labor charges and guarantees we often did cost analysis and were told to drop another powerplant in. Yur mileage may vary, as always, you can gamble and do partials as you or your tech see fit that depends what you find or want to spend. You can always ask mr. goodwrench to give you exactly what and why because he is dam near the best. He cannot stand to lie to you and always errs on the side of coverage and protection for you. Some folks say"I can do anything I want to my own car, and they are also right. Because its their credit card.

7,840

How do I know? i worked there. left there to seek green pastures because my ollady wanted to raise rugrats etc. but that's another story...A long time ago... nevermind.

12,535

If you have a blown head gasket or a cracked or warped head, a compression test will tell you which cylinder has lost compression because thee cylinder will not hold compressed air. After removing the heads, it is wise to do a through head job including getting the heads surfaced to insure they are flat. You also might have the engine checked to insure it also is flat, which it should be. Easy to place a straight edge on the top of the block and look. Make sure the engine and head is clean of all gasket and sealant before putting the new reconditioned heads back on. Good idea to have the cam checked for excessive wear also while the engine is torn down. Ig this is a first tear down and you have a lot of miles on the engine, a crate engine may be the best way to go. All new parts, guaranteed and a lot of less worries. With older high mileage engines, if only the heads are done, it will cause the rest of the engine to fail real soon as the compression is boosted back up and additional stress and pressure are placed on old worn and tired pistons and rings and main bearings. Just a thought. Check pricing first. If you're thinking of selling it, a bad engine vs a new engine will not see you getting you money back.

7,840

It really very seriously depends what engine and its age, the current manufacturer data, and publishings about it. The things that are done resulting in ineffective repairs or conversely simplifying repairs are not necessarily published info. after some success, an updated part and procedure bulletin may be superceding at your dealer, but not tricled down to the retail aftermarket. When it comes to your engine, be sure you discuss with the proper end of the horse, not see what was left in the wagon. Some of these wives tales result in excessive parts replacement as malpractice guessing. research saves time and money during the actual repair, but too many competing sources for prices ? Believing stories about a V8 in the 60's and applying it to today"s engines? not always the best. Ask the best, not the rest.

7,840

Find out what is the actual construction of my engine ? Not generally all engines. What has the factory been doing about the concern, is there a reason why? Cost only? If my rings are seated, and I have no ridge, and can see no O/R, taper, or scoring, why cant I fix mine my way? why? my readings across my cylinders compared on my repair order show they are close to one another, they are towards the high end of the spec, lets say, why do I need to hang a rabbits foot from the hood ornament, and circle the car 3 times before getting in? Just cause grampa blew his up ? His was a 58 dodge with a straight 8 or something, with cast rings, etc, I digress.

12,535

Dannyl are you off your med?

7,840

I thought you guys wanted the best advice to correct an automotive issue. This was exactly that. If you like doing what you do? perhaps you could take it where you are appreciated for it. I welcome your input, but I do not stab techs in the back or give attitude about replacing good parts with brightly colored garbage from overseas. I advocate measurements before condemning vehicle parts. I wont apologize for it. You can buy what you want and go have fun with it, I wish you well. in spite of the attitude.

7,840

You say, if an engine receives a valve job, the compression pressure will blow out the rings. please explain. when and on what engine have you tried this and had that for a result ? How did you arrive at that ? where have you been told that? I have heard it said by many a learned man, but considering what was meant about what engine, you must take it with a grain of salt, not tell people it applies in their case. It's like the guy from the south I worked with, he told customers that you had to replace additional parts on all jobs because the new part increases the pressure on the deemed serviceable parts causing them to fail right away. You kinda get tired of customers wanting that kind of thing explained.... He had just been schooled by word of mouth, had no formal training, and was repeating what he thought they said. It is not that he was incompetent, just that he was being pushed to go faster, and rewarded for magic tricks. It does not make him the problem, but shows he needed a mentor. That's all.

7,840

The sum up for this asker is have it checked and torn down by the chev garage, talk it over, learn what they would recommend and why. You can tow it somewhere and do whatever you like. But I have seen the GM garage arrange engine replacements customer pay, by negotiating. I have also seen partial engine repairs and done both and all the above at the dealership level, if that means medication is the answer ? pergaps the cooling system tablets GM recommends...Hahaha. it is a sign of intelligence to read and follow directions.

12,535

Dannyl, where are there any bad mouthing of mechanics? Where are there suggestions of buying out of country parts? Suggestion were given on how to test for either a cracked head, or blown head gaskets. MY suggestion was IF there is high mileage on the engine, a full tear down and rebuild may be in the best interest. PAST experience has shown old high mileage engines that get a head rebuild only MAY cause engine part failure earlier than later and to consider a total rebuild and or look at the cost difference of getting a crate engine. Yes the crate engines are made in Mexico, as are a lot of OEM engines. I bought a short block crate engine for my Corvette that had over 325,000 on it and a magna-flux showed there major cracks in the engine casting. The engine was cast in Mexico, but all parts were American made and assembled by a certified NASCAR mechanic/engine builder. If the head gaskets let go, it may be because of warping of the heard and or block. We don't know if the car over heated in the past and if so how bad and how many times or how hot it got. If the only issue is the gaskets, replace them properly and button it up and go. As long as the engine is torn down, it would be a wise idea to make sure the engine is sound so a n engine tear down wouldn't be in the near future. I re-read all the input answers and no where is anyone suggesting buying "brightly garbage from over seas," nor is anyone stabbing anyone in the back. All we gave are suggestions on what to look for, what may be the cause, and sage advice on preventing heart or head aches later on. I'm not looking for an apology for anyone. I really still after going over your answers am confused on what your real suggestions are. Old engine rings vs. new style engine rings? All engine rings wear over time, and just how many miles are on the 1992 truck, and how has it been used? If we were not sitting at a computer screen and guessing at what the real symptoms are we all could give a better suggestion on what to do and how to do it. So you claim to have been a factory certified or franchise trained mechanic? Well my friend, am I to be impressed? We all have titles behind our name. And DanS_WI to you I apologize for having to witness this hissyfit we seem to have going here.

7,840

Just dont tell people that a valve job damages rings without data, that is malpractice. all you can rightly recommend is consideration of readings and the opinion of the engine builder. It is wise to get those coolant damaged parts out if you find them. It is wise to do your math. Please dont deliberately misunderstand plain english. It shows that what you do is something other than effectively repair by industry standards, instead you spread misnomers and discredit those with credentials beyond your station. That is simple. Enough said.

12,535

I have been tearing down engines and rebuilding them since I was an early teenager. Granted it was on farm equipment, 50s and 60s car engines. I belong to a corvette club and engine discussions are going on all the time. I also have joined several car blogs, and discuss engine issues there also and causes and preventative measures. I have talked to many professional engine builders for NASCAR NHRA and other racing factions. To keep their door open they take domestic engine rebuilds and from their professional experience is where I have drawn my opinion along with all my engine teardown experience over the past 50 years of turning wrenches. I am not a professional mechanic, have worked in car repair garages after getting out of the Marines until I got my education degrees and full time professional job. Some times old mechanics without formal training or paper to adorn the walls have a vast amount of knowledge for the school of hard knocks. There are a lot of good garages that can do as good a job as car dealership repair facilities. Sometimes at a better success rate and less cost. No one is going to talk about the 1% of those that give the industry a bad name. Not from me, unless they prove to me they are crooks. So an engine that is 23 years old getting (I did not say valves) reconditioned heads, needs to be aware it can create other issues. the person having the work done an get another opinion, refuse to have additional work done or take advice and have it done or checked. A good mechanic will do this. Not just the GM garage.

7,840

I would point out simply that surfacing every head as you recommended earlier is also malpractice. That changes the compression of the engine and is not recommended. If you read and followed information that comes from the engine plant, or had all that experience, you would also know that the geometry of the surfaces in relationship to the intake is also affected negatively, an update is recommended by the factory that does not include your race car technology. The basic recommendations for proper care and service of THIS engine are not included in your recommendations. It is nothing personal and we all learn by reading more and talking to people who know. I had to be taught when I was an apprentice. I continue to learn. I also share the reality that goes with this pickup truck engine. No racecar parts are recommended, you dont have a rich sponsor, you are not trying to go that speed, for a few hundred miles, it simply is a different subject in this case. You would actually increase the leakage and run the bill up. disagree? try discussing this with mr. goodwrench, his cars also, in a different place have won more races, and produce more horsepower per cubic inch on the street. They are designed for what they do, specifically, I for one, would start by talking to that end of the horse. or fish, in your case.

7,840

I went to the previous posts and reread them all, the results you warn about are caused by your recommended process. You also have contradicted yourself. Take this thread and share it with your friends who know, and find where you can save money and produce better repairs, helping your customer and staying within GM spec, it's that simple. That can lower your cost and improve sealing, which was the cause of this guy's engine problem, following service recommendations of GM since it was new could have prevented his failure, or made his engine last till he chooses another. period.

20,825

wow......

20,825

does someone need help here???? if so, for what issue!

1 out of 1 people think this is helpful.
7,840

WOW, yea, the facts are in the service bulletins. machine work is not recommended just as stated. if the engine repair tech does not find it out of spec, there is no reason and the result would cause further coolant leakage. the tech would need a very good reason, then the cost would point him to a goodwrench replacement engine to save money in the long run, ask him. At your dealer, after they find any internal repair issue. just a leak is covered by the update. Wow, yes its that simple.

12,535

Dannyl, I had resigned not to respond to your incoherent rants. But I will anyway. I never said, nor had anyone else said, to pull the heads and re- surface them just because. If the heads were found to be warped, which can happen, a good suggested fix may be to put them on an engine head lathe and resurface the heads if that is the least expensive way to go. For some reason, either I need to go back to school and re-learn the english language you use, or you need to slow down, understand what is said, and not jump to conclusions and type rants just to see yourself in print. Yes surfacing the heads wi8ll cause an increase in cylinder combustion pressure, Not enough to make it a "racing" engine. If you would of read and understood what I typed, I said the racing engine builders also rebuilt engines on domestic cars. I did not state anywhere they make them all into racing engines. Where is your anger coming from? Do you think everyone is out to prove you wrong? You are on the wrong site for this type of psycho rants. Like I said, take your meds and slow down.

7,840

It's nothing personal, so try not to hurt yourself. The bulletins are a published fact and his dealer will advise. If he washed a cylinder(s) they could elect to save it. What they will not do is deviate from spec or build him a race engine. They also dont need any other technology beyond Gm's already proven recommendations. His choice can be anything he wants, after that many years, it's his decision to pay or play on his own. Gm will still tell him advice.

7,840

Try to stay on topic, please

12,535

So what I understand is if GM does not have it printed in the service bulletins, it is all wrong. I understand where you're coming from now. What if the person does not go to "his dealer"? That can happen you know, or is that a concept out side your thinking box? I don't worry about hurting myself. I have weekend passes from here twice a month.

7,840

Try not to take the right answers and injure yourself with them. Try to ask the people who know, as you claim you already do. published information is available to technicians. that is no secret. you are a helpful person, that shows you care. If you are misinformed, or attitude alone inhibits your doing proper research, dont get yourself offended. you just received information that is erroneous, or not pertaining to the man's truck. GM does not rebuild like the old days, they have technology to correct issues as they arise. I recommend consulting them. Again, it's that simple.

7,840

As already, and repeatedly stated, they diagnose and do partial repair, just like any manufacturer. They also offer more cost effective replacement. They use information you may not have, they prove their findings and then publish cost effective corrections. They protect their information so it is not erroneously misused. They employ people to answer you. They eventually release their data and specs as required. They warn their technicians not to do what you recommend. Its nothing personal.

25

Hey guys, thanks for all the help. It turned out being the Intake Gasket as the main cause of he coolant leak problem. I changed those and put everything back together, however, it does not seem to want to start now. It will crank just fine, but does not fire. I obviously had the throttle body off and the lines disconnected for a couple of days, do I need to work the air out or something for the fuel to get back up there? Does not seem to be getting fuel, don't smell it or anything when trying to crank it over.

7,840

verify spark, then if thats there, verify fuel pump... describe

7,840

you know it ate water, alot... what were the conditions in the engine? What were the results of testing? did not follow recommendations? Bak2 the basics, spark, fuel, compression, timing . verify basics , then get specific. its guided diagnostic so get the service manual. list equipment in use verify year make model engine trans, run codes, note conditions, warning lites, recheck previous repairs. system prechecks, fuses relays battery charged and has clean oil, does not smell like fuel there. blah blah, or consult a tech for basics if you need a trained eye. reread what we told you before. think about what you did because it did run.

20,825

i wish someone would ask me a question.... .............

7,840

allright kellym, what would you test first? to make his "v6" start in this case ? I noticed you thought he needs a timing chain and a booster before, what do you think now? does not hurt to ask.

7,840

He did what he thought after reading what we wrote, we do not know what conditions were verified or what tests were run or the readings or results. We dont know his cam or bearing conditions. he might be getting it to start to sell it, or trade it. who knows.

7,840

Aftertwenty some years, he may have a different engine or a low mile farm truck, so, how many miles are we talkin.? original? are there heat stickers on its heads indicating it was guaranteed by some reman or replaced as used? we need our questions answered before

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