Help With 5.7l In 95

jbbies · June 18, 2010

Ok, I have a 1995 GMC 1500 with 135k miles. It has been running great since I purchased it 2 years ago. Although last week it started sputtering and dying only for a half second around the 1500 to 2200 rpm range. I have changed the distributer cap and rotor, Coil, and fuel filter and still no improvement. I ran a fuel pressure test on it and it is right at 13 psi. Now it only does this when I am driving, and seems to be worse when pulling a hill, I watch the tack drop a maybe 100 rpm and then picks right back up. Seems to run fine when I am fully into the gas and idles fine as well. Seems to be just during mid acceleration at that RPM range. Do you think I have an injector going bad? Could the fuel pump be going bad but just not showing it on the pressure test? What do you guys think.

Thanks for the help Im sure someone will help me figure this out.

Brandon

jbbies · June 18, 2010

I guess I should add its the 5.7L

jbbies · June 19, 2010

Anyone?

Mike G · June 21, 2010

Have you looked into a rebuild kit for the TBI. It's tricky because like you said, it's the middle range of operation. Have changed the fuel filter? Does the throttle linkage show any signs of looseness or wear spots in the middle throttle range? I am just tossing ideas but it does sould like you are in the right ball-park with it being fuel related.

--Mike

mjlimo82 · June 22, 2010

Mine acted similar not too long ago... turned out to be the EGR valve. You can probably grab the codes by jumping the terminals and see if it tells you anything.

Patrick H · June 22, 2010

I'd check and or replace the Throttle Position Sensor.

Blue_Z71 · June 23, 2010

I'd check and or replace the Throttle Position Sensor.

This <<<. My '95 did pretty much the same thing. TPS fixed it (but ended up putting a whole new TB on it just in case)

jbbies · July 3, 2010

Ok.. So here is what I have done. I went through and had all the fuel injectors cleaned rebuilt the TBI system, new fuel filter, new cap and rotor and new coil. Ran fine for about 2 hours and then started into this again. It seems to be more prominent in the acceleration of the pickup and seems to run fine and a steady speed. It just cuts out I can watch the RPMs drop about 2 hundred and the oil pressure drops then it picks right back up. It will do this once then nothing runs fine other times it will do this multiple times in a row. What else should I be looking at.. Does this sound like a fuel pump?

green 788 · July 3, 2010

I'm assuming you replace the throttle position sensor, right?

jbbies · July 4, 2010

I have not replaced the TPS yet. Im going to replace both that and the EGR. Hopefully its one of these two its really driving me nuts. I did run a check on the codes and it didnt show any error codes that were stored.

Ill keep all you posted. Thanks for the help

B

jbbies · July 8, 2010

Ok I have replaced both the TPS and EGR valve. It seems to have helped as I have not noticed any problems yet however it still has a rough idle. Nothing crazy just at idle it drops RPMs slightly and you can feel it in the brake and seat. I did notice on the EGR solenoid valve there are two connectors on the side closest to the cab for vacuum lines. One is connected to the EGR valve but the other is open. I could not see any place where a hose was or could go. Is there suppose to be a vacuum line on this?

bronyaur · July 8, 2010

The bottom line goes to the EGR valve, while connection right above it has a foam filter of some sort connected to it. I doubt it would make much of a difference if that little filter was missing.

Here's a link to a website that has a photo. Click to enlarge and you'll see the little piece of foam on the connector.