Rough idle, slight miss cruising

lotzagoodstuff

lotzagoodstuff
Joined
Dec 19, 2009
My car sat for several years before I bought it and started putting it back together. I have it running and driving, managed to pass the smog test, but it's never idled as well as I think a stocker should. I now have a PowerLogger and all the numbers look acceptable, however, I still have a rough idle and a slight miss/hesitation when I am cruising at a steady speed. I am trying to figure out whether its a spark or fuel related problem.

I would swear it's a TPS going bad, but I looked at the sweep and its nice and smooth throughout the span of throttle. I have driven a couple of LT1s with bad Optispark, and it feels a little like that, however, it runs better under load, and my experience is bad spark usually gets worse with load.

It seems to pull ok under a load, but I also noticed it seems a little harder to start after I shut it off for ten to twenty minutes, like it might be a little fuel fouled. I am wondering if I have a bad injector (injectors maybe, they are original) or maybe a bad injector harness.

I have a complete fresh tune up, new FPR, DW fuel pump, just trying to get it running perfect while still stock before I do anything else to it. I have checked several times for vacuum leaks, and my PowerLogger numbers look pretty good to my untrained eyes. I also have no engine codes, so I believe the ECM and sensors are functioning properly.

Any thoughts on testing stock injectors and/or harness?

As always, any help is appreciated.
 
I have a thread going called misfire. Hope you find your problem. It sounds exactly like my problem. Good luck!
 
Check the EGR valve, disconnect the hose and drive it to see if it goes away.
 
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