Rough idle, slight miss cruising

[lotzagoodstuff]

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.

 

[asghert]

I have a thread going called misfire. Hope you find your problem. It sounds exactly like my problem. Good luck!

 

[tcgn]

Check the EGR valve, disconnect the hose and drive it to see if it goes away.