89 running badly

[89sub]

Help! I posted this in the Suburban section (it's an 89) but thought I'd try here: Recently the idle speed started coming up when sitting at a light. No check-engine light, but annoying. Passed emission testing same weekend. Went on trip, check-engine light came on once to destination, but idle speed back to normal. Pulled code 45 and replaced O2 sensor (and temp. sensor for ECM while at it) Runs like a dog--real rich and no power. Took to tech in Reno (on vacation still!) and he thought fuel pump. We replaced--nope. Still problem. He scanned with one of those expensive scanners that allows you to see what the ECM sees while driving. Only code 45--rich O2 sensor. We checked the following: MAP sensor, temp. sensor, EGR, O2 sensor, used smoke to check for vacuum leaks, replaced both TBI injectors (are dripping at idle and at speed--but have good cone around drips), spark, exhaust backpressure (at O2 sensor port) and probably other things I am forgetting (bad trip with family, ya know) The engine and it's accessories (including distributor) were replaced at GM deal 22,000 miles ago. He thought it might be distributor (although he checked spark--good) or ECM. Any thoughts? Thanks in advance!

[89sub]

I forgot to mention we checked fuel pump pressure and it was okay. Evap system was checked, as was the TPS. Probably some others I forgot. Thanks.

[rb1322]

I have a similar problem with my 1992 Chevy C-1500, with a 5.7 V-8. I got code 44 ( lean o2 sensor ). I replaced the sensor, Idle air control and fuel filter. When the truck gets to operating temp the idle goes up and down, and the check engine light comes on. As soon as I disconnect the air compressor it smooths out and will run fine until I plug the air compressor back in. I hope we both get help!! This is killing me !!!

[sak22]

I had the same problem recently in my 89 C1500... most significant was a loss of power, a big loss! I tried everything and nothing worked. Took it to the local Chevy dealer and they tried everything but nothing worked. However, one of the older mechanics who was very familiar with these older trucks said it drove and felt like a clogged catalytic converter... although their diagnostic equipment pulled no codes from the truck. So they did it the old fashioned way... they by-passed the catalytic converter by unbolting the Y-pipe from the manilolds, used a heavy duty exhaust strap to support the exhaust system and fired it up. They took it for a drive and although it was loud as hell, all the power was back! They installed a new catalytic converter and now all is well! I don't know how many miles you have on the truck/converter, but my 89 only has 120,000 original miles. So if mine went out, it's possible that this might be your problem. Hope this helps.