Une dernière pour la route ...
http://forums.aaca.org/topic/266805-an- ... ion-issue/
For a while my fuel economy on the good 88 has been less than it should have been even with my tendency to go heavy on the pedal. In addition I have had some harsh shifts and also a tendency for the transmission to "hunt" gears and not always activate the TCC between about 45 and 55 MPH. I suspected a transmission problem but never found anything wrong nor could I find a vacuum leak or other explanation for all of this.
Well, earlier this week the car started to run terrible. Lack of power and acceleration, rpms jumping around at idle and wanting to stall at stop signs and red lights.
Checked the MAF, IAC, TPS, O2 sensor via diagnostics and the other usual suspects no trouble found. Finally decided to swap the ICM. it wasn't a collapsed cat as that has been previously addressed.
I should point out that I installed a brand new Delco ICM and used coils on this car shortly after I acquired it a few years ago. Has always had the harsh shift and stumble between 45-55 since I owned it. Anyway, a replacement ICM not only solved the poor running engine but smoothed out the shifts, elminated the periodic stumbling and shuddering at highway speed and has markedly improved fuel economy already. Can tell it is running closer to spec and not rich as it was before the recent ICM swap (exhaust smell was noticeably rich). So, in the end, all these problems I had are attributable to the ICM. Appears it was faulty from new and suddenly got much worse forcing me to diagnose and change it. Since I previously suspected a transmission problem I never addressed it, expecting the tranny to let go and would just replace it then.
Worth adding that, as usual, no codes were set by the faulty ICM so diagnosing is strictly seat of the pants style with no help from the computer.I wanted to post this in the hope it may save someone else the aggravation of suspecting a marginal or failing transmission and a loss of proper fuel economy as I endured for a long time. I had no reason to suspect the ICM until the symptoms suddenly and inexplicably got much worse.
The frustrating thing is that had I suspected the ignition module I would have replaced it much sooner and avoided the mildly irritating symptoms it was exhibiting all this time. I'm glad it is fixed now, the car drives and shifts better than at anytime in my ownership so far. The inability of the on board diagnostics to recognize a failure of the ICM is a major shortcoming though. I do find it odd how much it affected the operation of the transmission, I'd not expected an ICM replacement to smooth that out.
In any case, another odd case for the files (seems like I get these a lot).
KDirk
