91, cuts out and bucks under 30mph/2000rpm

[FreeUlster]

I've had this truck over 10 years. I replaced a coil pack about 3 years ago. I also put a new ICM in at that time. Last year I replaced the plugs and plug wires. Now it will cut out when I'm trying to drive. It idles great and revs in neutral. When I put it in drive it cuts out even with the slightest amount of gas when i'm under 30mph and 2500 rpm. It will eventually get to speed but fight the whole way. Doesn't matter if the car is warmed up or not. Some days are better than others but generally the engine will backfire and cut out but I don't loose electricity. If I'm roling it will start again on it's own. I did put in another ICM that is known to be good with no change in behavior. Also I just got 42 miles on half a tank of gas. I need help.

Thanks Kent.

 

[VairKing]

Might have water in the gas...I know I had water in the gas in my truck and it would do that, a couple bottles of ISO propaline stuff and it was good to go...

 

[MNHawk]

I've had this truck over 10 years. I replaced a coil pack about 3 years ago. I also put a new ICM in at that time. Last year I replaced the plugs and plug wires. Now it will cut out when I'm trying to drive. It idles great and revs in neutral. When I put it in drive it cuts out even with the slightest amount of gas when i'm under 30mph and 2500 rpm. It will eventually get to speed but fight the whole way. Doesn't matter if the car is warmed up or not. Some days are better than others but generally the engine will backfire and cut out but I don't loose electricity. If I'm roling it will start again on it's own. I did put in another ICM that is known to be good with no change in behavior. Also I just got 42 miles on half a tank of gas. I need help.

Thanks Kent.

Try cleaning the EGR and the IAC. Seems like it would be more the IAC, but seems like you are getting the same LACK OF RESPONCE as I did here.

 

[FreeUlster]

Still need help

bump

 

[marragtop]

Look for vacuum leaks. Start with the vacuum tree on the drivers side near the firewall.

 

[FreeUlster]

I replaced the MAF and now I have new problems. Truck wont idle, drops below 500 and stalls. I have to put it in neutral when stopped and gas it. It drives fine but standing idle is bad and it is belching out black smoke and leaves soot on the driveway. The other problems are gone though. I'm starting a new thread.

 

[FreeUlster]

I replaced the MAF and now I have new problems. Truck wont idle, drops below 500 and stalls. I have to put it in neutral when stopped and gas it. It drives fine but standing idle is bad and it is belching out black smoke and leaves soot on the driveway. The other problems are gone though.

 

[mikeinri]

If it's running like that, you MUST be getting codes. What are the codes you're getting? That would help a lot with troubleshooting.

Mike

 

[levishake]

mine did the same thing, it wouldnt idle i had to put it in neutral at stops, it didnt set any codes off eather, I replaces the iac and runs like new. ( excuse any bad spelling)

 

[FreeUlster]

I just tried to clean the IAC with no residue, non-conductive electronics cleaner. Pretty soot filled. The shaft in the part with the two big holes seems to have some small holes in it but they look plugged. Is the unit shot?

 

[levishake]

i would say if it looks plugged then it's shot. you can use carb clean to clean it, the 2 ports are sealed from the electronic part. When mine went bad the inside was as clean as a whistle, the seleniod part went bad in it.

 

[FreeUlster]

Would this explain the rough idle and soot from the tail pipe?

 

[levishake]

yeah mine started out with the rough idle but i didnt have the experience with the soot from the tailpipe.

 

[JDraper]

I'd be inclined to think that the FPR may have gone bad. Black soot in the exhaust means too much fuel is being dumped into the combustion chamber.

 

[FreeUlster]

I went 20 miles on half a tank. What is the FPR?

 

[JDraper]

Fuel Pressure Regulator. Your fuel pump delivers significantly more fuel than the engine can handle, so the FPR meters it down. If it goes bad, it can flood the motor. There is a vacuum line that goes to it. If you pull the vacuum line and there's fuel at that location, it's shot. The fuel will be pulled into the motor via the vacuum line as well as the fuel line, resulting in a VERY rich condition. Do a search here on FPR and you'll find lots of info. Trace the fuel line back from the fuel rail, and it should be a round cannister with two fuel fittings and one vacuum fitting.

 

[FreeUlster]

JDraper, thanks for the info. I'll check it out. I have a fuel pressure guage I can use. Can I assume it will be well over 35psi?

 

[JDraper]

Not if the fpr is blown and sending fuel into the motor via the vacuum line. You might even see a low pressure on the fuel rails then.

 

[levishake]

I cant believe i didnt think of that, I cant even remeber how many fpr i had to replace because of that problem.

 

[FreeUlster]

Well I pulled codes and kept getting 12 MAF out of range. Took the MAF back to the flaps were I bought it and put in another one and it runs great.