wberkshire

here is the scoop. block was getting coolant in it and engine ended up going bad...normal. i put a new engine in (used w/ 15000 miles) and got everything back together nice. turned over the engine it started instantly fine. even idled fine at first. drove the car around to make sure everything was ok and everytime i let the car come to a idle it would shut off. after some discusion i put a new forward o2 sensor on. havent replaced the back because im running a catless pipe. (correct me if im wrong but i figured its useless to change it. i know it is throwing the cel but dont seem to think it effects the idle) once the new sensor was in it finaly idled on its own...after the car was warmed up. befrore the car reaches normal running temp it will still shut off at idle. any ideas?

RIWWP

iTrader: (2)

The front O2 sensor is pretty critical, especially to anything that is supposed to be closed loop, since it can't run closed loop without it. You were likely in forced open loop from the error, which is going to be rough going anyway. It's the rear O2 that is used only for emissions check and for fine tuning the AFRs under long cruises.

You could still have other issues:
- How is the ignition?
- Does it have enough drive cycles on it to stabilize the fuel trims?
- Is the block grounded sufficiently?
- Are the ESS and MAF clean and plugged in correctly?
- have you confirmed no vacuum leaks?

wberkshire

yea thats why i only replaced the forward o2. ignition is great still has new starter from trouble shooting the old engine. replaced all coils and wires and plugs when i put in the new engine. we even added a few grounds just to be sure so im sure thats out. ess and maf im pretty positive are good (ill give a wiggle tomorrow morning to check. ive started and driven the car several times the past few days so im sure the comps have all stabilized...not sure about the vacum lines though

RIWWP

iTrader: (2)

Don't forget everywhere that could cause a leak:
- Each end and length of every vacuum hose (EVERY one!)
- The gaskets between the upper intake manifold and the lower
- The clamp between the intake accordion and the throttle body
- the gasket between the throttle body and the upper intake manifold
- the covers on the lower intake manifold service ports


Though since the behavior changes with engine/coolant temp, I'm inclined to thing that this is going to be heat related, something either changing within the ECU that bypasses the problem (like fueling changes) as it heats up, or something that seals better as it heats up that isn't sealing well when cold.

wberkshire

that makes sense but could be pretty irritating to find out...been looking around on here for similar things. saw where i should take out the ess and clean it but that doesnt answer go off the lead of the temp change and it stopping