Fuel delivery stumper

I have a 95 Blazer 4X4 with 160,000 miles. It's been in the shop for a month and my mechanic has been unable to find the problem.

The symptoms are that it idles very rough, but runs better at high speeds. Seems that it is running too rich, to say the least. There is so much gas being delivered (or leaking somewhere) that there is gas in the oil.

He replaced the fuel injector unit and checked the feed lines into it. I think he pressurized the fuel lines and they held pressure. He has replaced plugs. Two Oxygen sensors were replaced 2 months ago. He's talked to a GM corporate troubleshooter to no avail. There has been a rattle in the catalytic for years, and he's going to check that next, but he doesn't think that is likely to be the problem.

I'm wondering if the fouling of the oxygen sensors a few months ago was the first symptom of the current problem.

If anyone has run into this or has any ideas on troubleshooting I'd really appreciate your thoughts!

John

I highly recommend replacing the fuel lines when replacing the CPI unit.With fuel in the oil, sounds like a injector or fuel line leak.
Secondly, have you check the EGR valve for being stuck open?
Check the coolant sensor..might be reading to low of a temperature.

Fuel in the oil? Sounds like your carburator is wacked. Let me know when you find your fix, Good luck.

Update: We found zero compression on one of the cylinders. Problem was a broken valve spring. Haven't repaired it yet but hopefully that will solve it.

John

had the same problem, are you sure the fuel lines going through the plenum base were replaced, I have the same symptoms and when I removed the upper plenum and turned the key on you see gas pissing out the side of a cracked gas pipe, and a gas puddle.the leak stops after a few seconds but i'm sure that when running it has to be leaking.