I am new at this. i am working on a 93 ford f150 4.9L. when it came to me it did not run at all. after checking everything possible i discovered the exhaust was plugged and fouled or burnt the plugs. so i did a tune up on it and fixed the exhaust. now it will run but doesn't have power. and seems to be getting to much gas. any ideas?

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Asked by May 14, 2016 at 08:33 AM about the 1993 Ford F-150 XL Extended Cab LB

Question type: Maintenance & Repair

32 Answers

12,035

The 4.9 6 cylinder had a blocked catalytic converter? I suggest you compression test it.. or one step better is to preform a leak down test then you'll have a basic idea of the overall condition of the engine. Read the codes too old EECIV you don't even need a scanner. Regards

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Compression was good. 148 psi plus or minus with little to no leak down. Every cylinder is getting spark. Timing is right on. Turn key and fuel pressure is 35 psi. Turning over fuel pressure is 55psi. @ fuel rail! Only other things i can think of trying is quality of fuel and vacuum leaks. Let me know what you think?

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Also has new coil. I pulled the vacuum line off the fuel regulator and it was dry plus has good vacuum so i assume it's good. I can't remember the exact name (brain fart) but the control module in distributer is replaced too

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Also not sure if it is supposed to do this but when you turn the key to the on position and the fuel pump comes on it had 35psi while the pump ran and built pressure. BUT... when the pump shut off the pressure leaked down to zero Immediately. Is it supposed to hold pressure or was it supposed to bye pass or something?

12,035

Looks good so far at least I'm dealing with someone who knows what there doing! Yes, the regulator is Ok if dry. There is a check valve in the fuel pump that supposed hold pressure..BUT right now that's not whats going on. How many degrees of timing do you have it set at? and you changed the TFI (thick film ignition) Check back 15 May, afternoon I'll look over the injection info, and be back online.

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I'll check the timing again and let ya know. I didn't write that one down. But... do you know how many ohms of resistance the injectors should read on this vehicle? I checked #1 and it read 13.9 ohms. To check the rest i need to remove the upper plenum. And where would the o2 sensor be located on this vehicle? I don't remember seeing one when fixing exhaust when truck was on the lift. At a quick glance from above i did not see one either today.

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And thank you very much for your help!

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I don't see an o2 sensor on this truck anywhere! Could that be the entire problem?

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Cylinder 2 injector shows 13.9 ohms also

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I found out where the O2 sensor goes and put one on it. They actually took the O2 sensor off and welded the whole shut. It's running much better. In park it starts and runs good. In drive it bogs down and you have to peddle it to keep it going. And the check engine light is on. But I can't get this thing to flash codes. I used a jumper wire on the eec under the hood. Any ideas?

12,035

Excellent you diagnosed a NO 02 sensor.. that is one of the MAIN controls active AC current square wave sent to the EEC that's trying to control the fuel mixture ratio and maintain the 14.7 fuel trim..now you can try and read codes did you connect the STI single line (jumped) into the test connector pin 2 narrow edge of test port top right.~~ KEY ON ENGINE OFF (KOEO) TEST NOTE: On 4.9L trucks with a manual transmission hold the clutch pedal in during this test. 1. Make sure engine is fully warmed. If in doubt, run engine at 2000 rpm for 2 minutes. 2. Turn ignition off and wait 10 seconds for system to shut off. Make sure A/C is off and transmission is in Park (automatic) or Neutral (manual). 3. Hook up light and jumper (or a tester if you have one). Turn key to ON (do not start engine). 4. Fast Codes are output (ignore fast light flashes). NOTE: Unhook self test input jumper (or tester if used) at any time during code output to erase memory. 5. Read hard faults. 6. Separator Pulse. 7. Read memory codes. 8. See code explanations and check components as necessary. Use FIRST CODE OUTPUT and retest after any repairs are made.(1987 -1995) SPEED DENSITY fuel injection. This system functions by taking measurements of air temp, engine temp, rpm, manifold pressure etc. is used to calculate airflow and then guess how much fuel the engine needs to run properly WERE LOOKING FOR CODES RELATED TO FUEL METERING EVEN TPS Throttle position sensor.

Best Answer
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Omg! This thing seems to have problems with every sensor on it. Is this from driving it without an o2? And could it trash every sensor? 558 EGR vacuum regulator solenoid / circuit failure 126 map sensor out of range 123 throttle position sensor was high or short to power 113 air intake temperature sensor out of range 337 EGR feedback signal is/was high Should i replace all sensors? Or should i check each one?

12,035

NO, not every sensor is trashed! First the 126 MAP is (manifold absolute pressure) this is the "upstream" fueling sensor it can be checked simply by unplugging it and observing the engine..The 558 EGR (exhaust gas recirculator) can have a carbon build up,this usually causes rough running DISREGARD for now..The 123 TPS is most likely a problem 23 years old. does the throttle respond smoothly when pressed? 113 Minor not a problem now.. Next 337 is saying hey the EGR valve is Stuck or none operational.. SO clear all codes now, Oh whats the timing at 10 BTDC degrees? SPOUT Unplugged. KEEP GOING JIM LOL

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I tried clearing the codes 2 different ways (thinking some would go away after replacing the o2) but of course it either didn't work or the codes stayed or came right back after just turning the key to check the codes if that is possible. The two ways i tried was one disconnecting the battery for 10 mins or more. And two was disconnecting the ground off eec while codes were being displayed.

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Also... should the timing be at 10 BTDC? I have to admit i don't know how to use the timing light i have yet. It is the light with the degree dial on the back. Now... on an idle when unplugging the MAP i observed no difference in the way the engine ran. Not sure if that meant it was good or bad though. And... the throttle responded smoothly when pressed. It seemed to respond right on without delay. But i was gentle with it too. I did not get on it or snap/pop the throttle.

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Ok... would it be timed right with all the codes on it has? Do I need to get it timed first. Or replace bad sensors first? And what I meant about timed right on was with #1 @TDC the rotor pointed right at #1 wire.

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I am assuming they did not touch the distributor! So if all sensors are working soon it should run good. But I didn't expect them to get rid of O2 either lol!

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I just smoke tested it. All is good. But it was leaking past the EGR valve some how. Does that mean it is bad? Sorry about swamping you with questions.

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I'm not sure where the smoke was coming from on the EGR valve but I went and bought a vacuum leak test tool and checked the vacuum on the AGR. It did not leak down and it worked perfectly.

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I know this is a lot to go over. I hope you are a patient person lol! I bench tested the MAP sensor and it failed. Hopefully that goes with the tesk of unplugging it while running and observing the engine.

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Ok i am done for today. So let me know what you think about all this. I need to know for sure about the codes and the timing too.

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I hope you didn't give up on me! I replace the MAP sensor. Cleaned and checked EGR valve. Replaced the TP sensor. Fixed vacuum leaks. Cleaned Pcv valve. Let it sit over night with the battery disconnected to hopefully erase codes. Drained the gas and put 5 gallons of fresh gas in it with Sea Foam and Thermo-Aid additives just in case. Checked the codes again and all of them are still there! 8, 637, 126, 123, 113, 337, 654, 558, 629, 626. Please help! I am now lost!

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Just so you know the MAP sensor is getting 5 volts and has a good ground.

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Also while running, it is smoking alot still. But seems much better. And when driving it, you can not go heavy on the gas peddle or it hesitates. It also seems to shift early. I would assume that's from lack of power.

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Well... i need to do a cylinder balance test. Not sure how yet! But I'm thinking i have a bad injector. Code 8 implies a cylinder is not firing i guess. And all of them have good compression and spark so injector? Still not too sure about this forum. And the lack of info is discouraging. I am new at this forum stuff. And i usually don't work on vvehicles this old. I'm not too familiar with obd1!

12,035

Hi, Jim I work a lot so I just read all your new info! 23, May 2016 since you have been through the entire system here's whats up Pull the EECIV computer its easy to remove, disconnect the battery first.. Next, take it some place where you can sit down with good lighting and Inspect it remove the covers there are 3 blue capacitors look close 1 or more is leaking or the PCB has a bad area there printed on a green board you will see it... AFTER all you've done when a computer throws codes like a shotgun ITS time to check IT. let me know what you find CONTACT me by email . Regards Oh, I don't give UP!! LOL I will check back here 24, May and 25, May

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Thank you! I took a break from it. I'll check the computer today or tomorrow and get back to you.

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The cylinder balance test left me lost so far. So i took the computer out and looked inside it. It looked bad like you suggested. So i ordered a new one. I will be putting it in today. And i will let you know what happens.

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I replaced the computer and it runs much better! It stopped smoking and it has power again. And NO check engine light! But...it still has a missfire. It is finally getting there!!! Thanks! So...what next? Cylinder balance test again? Bad injector?

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12,035

Very good the computers do go bad after many years!

12,035

Double check which cylinder has the misfire. That is step 1. Again then inspect the wire and plug,(is it wet) Injectors are very durable they don't fail often but that 300s might have debris in the injector pintel.. Oh, Jim you now have the basic understanding that many "techs" are clueless OF! you're into the last details of fine tuning.

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It is not running perfect but good enough for the customer. He is going to try to drive it around a bit and see if the check engine light Comes back on or maybe it'll just get better. It might just need driven. You were right the injectors were good. Each one was around 14.8 Ohms. But it has power and the check engine light is off. So thank you very much! If it comes back i might have to consult with you again. Take care

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