[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.