Kermit and I tried to figure out some of what is causing the stumbling/power flat spots/CEL that I have. We couldnt come up with anything solid, just an agreement that 0171 and 0172 are fun
codes to track down.
Anyway, the car is a `96, it has 130K on the clock and an automatic. Its pulling p0172 and p0171 is usally with it or pending. I am curious how I can be getting a rich and a lean code at the same time? I figure that this is probably part of the flat spots in the RPM range, perhaps rich at idle and lean at the upper end?
Anyway, aftermarket intake, checked it for leaks already. Clean air filter. New fuel filter, and new upstream O2 (I was getting sluggish readings). The old O2 was in the high .3v range but didnt react fast. The downstream is 40K miles old. Otherwise, the only other mods to the drivetrain are the flowmaster, mystery mod, and MIL eliminator on the downstream sensor. Even without the MIL eliminator, I was still pulling 0172 and 0171, not 0420 like I should have been. The PCV valve was replaced about 20K ago.
The car idles at 500 rpms, per the tach, doesnt matter if I am in drive, neutral or park. It will fluctuate about 50% of the time between 500-750, sometimes, the differences in idle are only 500-550. It can still be felt though and the needle on the tach does show it.
The plugs are about 30K old, and their gap is holding. The wires are 20K (originally replaced at the same time as the plugs but after 10K the replacement set fell apart and was replaced under warranty). Resistance on the wires is well below Ford's discard of 6000 ohms/foot.
The flat spots are idle, when the car has a slight stumble. If you get on the throttle to bring the rpms up to 1000 before taking off this problem goes away. It sees another flat spot between about 2K-2.5K rpms and then another between 4-5K. Its enough of a ddifference one of my friends who has been out of town for while commented that he thought it had slowed down.
And finally, whatever it is doesnt completely go away when the CEL kicks on. The car still acts weird, which would have me thinking it is a mechanical problem that the computer cant control. When the CEL is turned off, I have about 100 miles of driving before it comes back on. Those 100 miles are quite miserable too.
Search tells me that most of the stumbling is at low end and doesnt reappear at high end. Most of the time, it seems like it comes down to plugs and wires, which I know are fine.
