Idle problems
 

I have a 95 Jimmy I just bought. I really love this truck but am having some issues with the idle and surging at cruising speeds. If I start it in the morning to warm up and let it run 10 minutes or so when I get in the SES is flashing which according to the manual that is a misfire code. I have had a constant SES and it read PO172 which is a system rich code bank one (I think) I have replaced the O2 sensor before the converter, basic tune up, cleaned the EGR still a very rough idle and erratic acceleration from stop. after reaching cruising speed seems to want to "surge". I don't really want to spend a bunch of money replacing needless parts to figure this out. I am leaning toward the cataylitic converter? The previous owner said they replaced the CPI spider with a used one...could it be that? I also read one of the threads where it wound up being a re-torqeing issue on the rockers any ideas on what route I should take first would be greatly appreciated

P0172 - Fuel Trim System Rich Bank 1

This code does not mean that the O2 sensor is bad. It could be a number of different things as the diagnostic post about it details.

I find it curious that a '95 with only one upstream sensor would know that it is a bank 1 problem... LOL.

Anyway, I would run a fuel pressure and leak down test. The fuel pressure should be ~60psi key-on/engine-off and should not drop below 55psi when you turn the key off. If it drops quickly to zero, you need to pop the MTV (the round plastic thing under the 'vortec' cover on top of the engine) and have a look inside the plenum for puddles of fuel. If you see puddles, your next step is the removal of the upper plenum to determine exactly what is leaking.

Thanks for the advice. today the tranny shot craps! Revved up going down the hiway like it was in neutral and then made noises like marbles in a can and now I have now reverse and it will only shift the forward gears manually.....sometimes. So once I get this tranny stuff worked out I will do a leak down test and check the upper plenom...thanks for the info

hi Kyle, where abouts should his fuel pressure be while its running?