Rough runing '94 C1500

Smokehouse69 · May 24, 2003

My truck just crossed 100,000 miles and for the first time I'm having problems I can't solve. I replaced the EGR at about 80,000 and the water pump at 90,000. For about 2 weeks the truck has been really acting up. It starts fine and for about 1 or 2 minutes it runs fine, then it starts stuttering and missing at light cruise or idle while in gear. If I put it in nuetral or park it idles perfectly. The ECM is not throwing any codes, so I've started changing parts.

So far I have replaced the distributor cap, rotor and wires, fuel filter, air filter, TPS, temperature sensor, O2 sensor, MAP sensor and EGR solenoid. Nothing has improved the performance. At anything over 1/2 throttle it runs great and pulls strong, no missing or stuttering. What else should I look at?

Sorry this is so long!

Fishhunter911 · May 24, 2003

I was gonna suggest a full tune-up but you have done that.... My 96 tahoe was doing the same thing and I did a tune-up and it all went away.... did you reset the computer after you did all of this??? It might still be over compensating for a bad part. Just a thought... sorry I couldnt help more

BadBowtie · May 24, 2003

I was going to suggest the TPS, but you did it already. For the amount of time and effort that you have put in solving it, it might be worth taking to a mechanic and having them put it on a scope.

-John

Smokehouse69 · May 25, 2003

I guess going to a mechanic will have to be my next step, I really hate to do that. I have always done all my own work, but this one has stumped me. The only thing I haven't tried is rebuilding the throttle body, but I really don't think the problem lies in the TB, since it idles perfectly in nuetral and park, and only starts missing and chugging when in gear. The idle will purr along at 600 rpm then jerk down to 300 for a second or two and then back up. Having the A/C on really seems to put the hurt on it too, like the load on the engine from the compressor causes it to lug down.

I'm going to pull off the EGR in the morning and make sure it is still working, since the car really ran bad when the EGR failed last year. The only difference is that last year I was getting check engine light and the ECM flashed the code for a failed EGR. This time the ECM is shows no trouble.

BadBowtie · May 25, 2003

I agree about doing all your own work, however, to save a little time and agrivation, they can pinpoint the problem. or at least point you in the right direction.

Smokehouse69 · June 1, 2003

Well. I got it running right, finally! It was the last thing that I checked, the freaking EGR valve. I just replaced it last year and the Autozone Wells POS had failed. What I can't figure out is why I never got any error codes from the ECM. When it croaked last year, I got a specific error code (I think it was a 43) but not this time.

Oh well, I guess I can't complain too much the truck runs as good as it did new, with all the new parts and the complete tune up. Actually it seems to run better than it did when I bought it back in 1994.

Thanks for the suggestions guys.