I have a 91 Z28 thats having idle problems after its warmed up. I have fixed a couple vacuum leaks at the pcv system where is screws into the intake manifold. I also cleaned the EGR valve and passages in the runners. All of this made it idle much better....along with adjusting for minimum air and checking the TPS for proper voltage. My question is, would my coolant temp sensor cause my car to run rough(and extremely rich) after it warms up? All ignition components are new, as well as the 02 sensor. I plugged up a scanner to the ALDL with no luck...shows all sensors as working....but thats it. Ive had a 170deg t-stat in my car for over a year now, but never had this problem from that. Im stuck...and need some second opinions on what else to check.....only thing I havent checked is timing...but it "seems" ok. I had the car out on the Interstate running 110....doesnt cut out or anything. Like I said before, it runs good while cold.....just not after it warms up. I dont have my catback on yet, just the exhaust from the headers back to the dual cats....would that cause the EGR to act up from lack of backpressure?????? Please help...this is driving me nuts. My new Tahoe is easier to figure out...lol

 

Guys? Gals? Anybody??????

 

Yeah, a misreading cts could do that. You can test it to see if it's in need of replacement.

 

Did you happen to look at the temp???

 

I had that problem on my 90rs. i replaced everything.. and found out the hard way. ended up being the water temp sencor. my car would run fine untill the computer started reeding the sencors. at that point 10 or 15 minutes later the injectors would go crazy and pump feul every where. and black smoke would pour out exhaust. the sencor is onlu like 15 bucks try it.. if not you have new temp sencor. i would say try that first.

 

oh dont run it to much when it is shooting out black smoke (unburnt feul) it will clog your cat(s) if you run it to long. .. i did that on a carburated ta .. new cat clogged up in like a week on a extremely rich carb.

 

Thanks for the tips. It turned out to be a bad coolant temp sensor. I have since replaced my L98 with a stroked LT1......

 

Wow, he needed a new sensor so while it was out he installed a punched out LT1. Now that's extreeme!:rockon:

 

LOL.....actually I had been having it built for about 5mths, so it just kind of worked out that way.......but thats how you take car of the TPI's trouble...just put an LT1 in it....

 

hmm.. i like that idea. my minds made up. when i have to do the next oil change ill just slap in a new ls6 insted.. :lala: ..