Rough Running Engine

My 1995 Chevy Z-71 was running fine until I slowed down for a stoplight yesterday when it died. It started back up but continued to run rough and would die if I did not put it in neutral and give it some more gas. When the light turned green, I took off but it was acting like it wasn't getting enough fuel; hesitation, jerking etc. Finally got up to 55-60 mph but when accelerating, it would still hesitate. When I got to the house, it died in the driveway, but started again, running rough. The fuel was less than 1/4 so I thought maybe some trash plugged up the fuel filter. I changed the fuel filter but still have the same results. The spark plug wires all appear to be in good shape and in place.

There is no "Service Engine Soon" light on or any other light on.

Any suggestions?

Also, I'm [over]due for a follow-up on my check-up by the transmission place - had that replaced around April-May... Running problems started the day I got the truck back - but had been sitting for mayvbe six weeks prior to replacing the 4L80E transmission.

Someone else suggested I ask about the 'modulator valve'...

Any thoughts on this?

I actually now need to solve my starting problem before I can proceed anywhere with confidence - - the battery seems good, and had a new alternator put in a little over a year ago... I'm expecting it needs a new starter - if/unless I can eliminate wiring/connections in the process.

If I can figure out the starting issue, I'll probably be in for the tranny check-up yet this week.

Thanx again!

Danauthier,

Thanks for your reply. It turned out to be my fuel pump. I bought this truck brand new and this was the original fuel pump. Not bad for 172,000+ miles.

It has been replaced and now runs fine.

Hello -

so sorry to confuse things with info about the other truck - - the starter issue is actually with the Silverado (not the dump truck)... Anyhow, it was at the store that we confirmed the battery was good, but an issue with the starter - just not sure if I only need to replace the solenoid or the whole starter. Working on this now.

Your description of the idle air control valve (idle speed control actuator?) ". Will cause an erratic idle and the engine to die at a stop" describes my symptoms perfectly. Yes, the Fuel Pump relay seems easiest and cheapest - could it be that this sends a signal/power to the IAC? Otherwise it seems like I may need them both.

I'll try the relay 1st - and then - if not solved - the IAC is my [final!] Hope!

I'll post my results.

- PR

Okay -

... Long day... Replaced my junk starter - one success!

I also removed and 'tested' the IAC - - by checking the ohms on each pair of contact points in the plug receptor - I got a steady 45 (or was it 54?) On each pair (the Haynes manual says the range should be between 40 and 80 ohms). This seems to suggest that the part is working... But the problem persists! I also 'checked' the Fuel Pump Relay... I don't have a matching relay - - it seems that it should either work or not - - and I never get no gas - just the wrong mix and absolutely errant idling. Oddly, I get gas with as well as without the relay in place! Shouldn't it kill altogether without the relay - just like a blown fuse? I also noticed the 'feul sol' fuse was missing - I replaced it with a 30 amp fuse - but don't know what this might affect.

A friend may have a matching IAC for me to test against this apparently (but not certainly) working one of mine - if that affects the performance, then I'll know if it's the cause...

- PR

Nothing melted by the relay I can see... I did notice that the whole fuse box is under the hood - - in my [Haynes] manual it says that the fuse/relay box should be behind the fire wall in the cab on a '95 model truck - and where it actually is on models '96 and newer...? Why might this be? I believe I have a '95 Silverado.

My truck starts/runs fine when cold, when reaching operating temp the service engine soon light comes on intermittently, starts to hesitate and run rough, sometimes stalling. When hot, it's very hard to start, you have to hold the accelerator pedal to the floor, and it blows black smoke, running very rough, until it smooths out some. I obtained codes 15, coolant temp sensor, and code 32, egr, from the ecm. I replaced the following parts- coolant temp sensor, egr valve, egr vacume solinoid, fuel filter, air filter, throttle position sensor. After replacing these parts there has been no improvement, ecm still shows a code 15, but the code 32 is no longer there. Please Help ! Thanks

Engine Performance problem
1998 Chevy Silverado V8 Two Wheel Drive Automatic

I have a 1998 Chevy Silverado that has a running rough issue.I have replaced all 4 oxygen sensors and the feul regulator per the trouble code generated by the PCM. Now when I go to start the engine, 2 of the cylinders are filling up with feul and wont allow to it to fire up. Thanks for the help

Thanks DennyP.I have ordered all new injectors:)

I am 18 years of age live in cold MN and my 92 Chevy truck is ******* me off. This all started a couple months ago it would start up and idle rough for a couple min of me holding it at 2500 rpms and then would run fine cleared right up, as time went on it slowly got worse as it will not clear out. So now it starts runs rough for maybe 15 seconds and then without doing anything it will smooth out, the check engine light comes on but once I try to give it any gas it chokes out. I cant drive because it has no power and will backfire on me. I have replaced everything from the fuel pump to the egr, tbi, map sensor, temp sensors. Etc please please help. I have been working on vehicles for a while and these trucks are nothing new to me. This thing has me flat out stumped.

Great site :-)

I have a 1996 chevy 1500 5.7 I have put a new distribitor, timing chain, fuel pump and had a shop put in on a scope. If I let it sit over night and start it it runs great for about 15 mins after that it runs bad. I can shut it off and start it back up and it will only run good for a min or two and then it starts running rough. No one can figure out what is wrong. Thank you