Contour Enthusiasts Group Archives Forums General Troubleshooting I've tried EVERYTHING...

Okay, the symptoms are: surging idle (which disappears temporarily any time the computer's memory is wiped), most pronounced when halfway warmed up; occasional CEL, with code 0171 "too lean", that appears when climbing or accelerating; significant loss of power, and mild loss of mileage.

Here is what I have already tried:
- look for vacuum leak
- injector cleaner in tank
- fuel filter
- cleaned MAF (soaked with brake cleaner)
- remove CTA and put stock intake back on (for smog inspection)
- restore CTA, double-checking for non-airtight joints
- look harder for vacuum leak
- replace PCV valve (the old one looked perfectly good)
- check EGR valve
- check all PCV and EGR plumbing as thoroughly as possible
- more gas tank injector cleaner
- (getting desperate now) replace oxygen sensors
- pull out fuel rail, inspect and watch it squirt into open air... no sign of any clogging

An inspection of the spark plugs does not show the pale color associated with a long term lean condition. If anything the color is on the dark side, though overall the plugs look healthy.

I don't know what to think, except maybe there's still a vacuum leak. That would explain the idle trouble. But how could a leak explain the lack of power with throttle >50%? It would have to be huge.

The only thing I can think of to try now is to get a hand vacuum pump and try pumping out various vacuum circuits and see what holds air. There are four vacuum hoses attached to the manifold. There is also the EGR pipe. The other possible points for vacuum leakage are the manifold's gaskets...

Or maybe there could be leakage down in the crankshaft chamber, letting in air (or exhaust) through the PCV. My god... maybe the piston rings are leaking... hot exhaust blowing back into the intake manifold... no, that would get tons of oil into the PCV, right? There was no oil to speak of in there.

I guess another possibility is that the EGR is open too much of the time? But again, I can only see how that would affect idle, not running at high throttle.