Got the FPR,EGR and EGR solenoid in last night after work. Started up perfectly, idled perfectly, then experienced one single stumble. Its running very smooth otherwise.....has an occasional tiny bump in idle "sound" which I think could be an injector drip. Not a big deal really.

I do want to cure the stumble though. Gonna try the IAC motor cleaning. Also, is there a chance the o2 sensors could be fouled like a spark plug? When the opti was acting up the engine was running very poorly...barely running and hard caughing. I had to really work the throttle to get it started at times which would cause it to smoke black and grey. So I wonder if you could clean the o2 sensors...

All the plugs I removed looked decent except for 5 & 7 which were blacker than the others. They all smelled like fuel...some worse than others.

 

yes 02 sensor can foul just like a spark plug, it can show a lean condition when condition is normal. starts a domino effect adding more fuel. you can clean them with a good acetylene torch. heat with hot blue flame and black stuff burns off. heat only the end that goes in exhaust and dont get them to hot, can melt wires. cleaning and flow testing the injectors is a good idea. especially with a car thats sat for a long time. injector shop can do it and its not that costly. way cheaper than new injectors and you know for sure what the flow is and that all of them are flowing the same. i like to have mine done at about 60k miles.

 

Cleaned up the IAC valve. It wasnt really dirty...but, sparyed a little brake kleen (no carb cleaner on hand) in the ports of the TB and wiped off the tip of the IAC itself. Really no difference. still get that one stumble, then its all good. Tomorrow Ill try cleaning the the o2 sensors. I only have a hand held propane torch, will that work? Can I spray them with carb cleaner or brake cleaner?

On a seperate note, I decided to take it on its first run over a mile or 2 from the garage. I drove it up to the top of 8 mile which is where the Royal Gorge Bridge resides by the way.... 24 miles both ways. The engine is actually running phenominally well. Ive owned many cars, from gen 1 small blocks to the mighty LS6 in my 02 Z06's....to an LT5 in my 92 ZR-1 and of course 3 other LT1 powered cars. This engine is still very much alive and running very strong. Im very impressed with the car overall. Really was well taken care of by the PO. I think I really got lucky with this one.

 

So, Ive tried several different things to cure the idle issue....

Replaced the temp sensor in water pump. PO said he did, but I wanted to be sure.

Replaced the IAT

Removed the o2 sensors...they looked pretty good, just wiped them off with a rag.

Reset IAC

Nothing is working.... Im about to pull my hair out. Made an appointment with a reputable local shop to check it outr for me on the 15th... The only sensor not replaced on this engine is the knock sensor! Im guessing the PCM might be the problem.... I dunno, just really getting frustrated...

 

Clean an O2 sensor? Visual inspection of an O2 sensor? That's new to me.

 

Craby suggested I burn off the soot with a torch...but they had just a little bit of black on them, so I simply wiped them off....Not to mention, that I doubt they are the issue because the issue only happens when the car is cold. Once warm, it idles perfectly, which would say the o2's are operating ok.

 

have you looked at the egr yet? maybe test the evap system.

 

EGR valve replaced along with the EGR solenoid. My Mighty Vac broke, so I havent had a vac pump to test everything in the evap system. I did however replace the evap purge solenoid when I got the code 26 a week ago or so. The only 2 things left in the system would be the canister itself and the evap pressure control valve....

 

this is sounding like one of them things thats so easy its not. i think your going to need to put it on a diagnostic scanner that will show the outputs of your systems. then see what the sensors are seeing when it misses. if i remember right you have replaced the opti. what kind of miss is it, a complete cutout like the ignition is turned off for a second? or maybe like its searching for the correct idle?

 

Its a cut out that dives down to almost stalling, then returns to normal idle....every once in a while it does die.

HOWEVER.....This morning after unplugging the air pump and starting it, it idled fine. I dont know if you looked at my other post about the air injection question....look at it if you get a chance.... but I think Im on to something here. The true test will ne in the morning tomorrow. I have the new air pump installed and everything is buttoned back up. If it starts and idles fine in the morning again, like today, I think Ill say its fixed. Im a bit gun shy to be able to say that now...

Took it in today to have the AC system charged. I have a nice cold blowing system now...man its really nice having it work on a day like today...90+ degrees.... no idle issues with air on either.