Hi, All:
I have not posted to this forum for TWO AND A HALF YEARS!!!! And that's a VERY GOOD THING, because my 83 Eldo has been running flawlessly for that long. I keep very careful records and in the last 2.5 years, I've spent a grand total of $125 on things other than routine maintenance. So much for the good news, now for a little hiccup.
Car was idling fast, affecting gas mileage. I could smell gas while the car was idling in park. Took it to a trusted mechanic, who said that for some reason that was above my head, he could not adjust the ISCM. He had to shim it instead. Well, he retired and moved to Tampa. A week later, I could still smell gas. Took it to a new guy who also targeted the ISCM.
He said that the motor was hard to adjust because (a) it is shot, or (b) the motor might be fine, but there are other things that could make it hard or impossible to adjust.
Because the motor is only 40 bucks, I am tempted just to get a new motor, as opposed to spending a couple hundred diagnosing the problem, and maybe just having to get a new motor after all.
What do y'all think?
Hmmm....
Sounds like it could be a bad ISCM or a bad TPS.
Is the car surging abnormally? (Revving up/down to the point of almost stalling and/or stalling altogether) - as this is usually what occurred with a faulty TPS in my experience.
I do not recall the smell of unburned gasoline either - so this may have nothing to do with the TPS or ISCM at all. Indeed, this could be a completely separate issue altogether.
Shimming anything is not the way to correct runability issues with any HT 4100 or newer Cadillac engine.
A couple hundred dollars sounds awfully excessive for diagnosis for something as basic as a 4100 these days. You should make some inquiries with the Club for recommended Cadillac specialists in your locale.
This is all I have to offer; no doubt others will have more suggestions. Good luck.
TPS... Throttle Position Switch? I'm pretty sure I have an issue with that; on very cold days, the gas pedal flutters for a few minutes until the car warms up.
If the base idle was played with this can cause the tps to be skewed, or it is bad or out of adjustment, that must be checked or corrected, before blaming the idle contorl motor. The obd can be used to check the tps readings at low base idle, it should be about .5v at the connector.
I HAD THE SAME PROBLEM... as did another member several months' ago... your idle speed control is LIKELY gummed up. It was originally packed with grease... and that has turned to non-lubricating crud. If youre fortunate, you can carefully disassemble the unit, (those four nuts--- be careful), and clean it out, and re- lube. Before you put it back on the car, reconnect the plug, start her up, let her warm up... see she stays running... and then watch that little shaft move in and out... it travels constantly, getting prompts from your computer youre good to go... if the little gear is stripped, you'll feel the electric motor turning, but the shaft won't move , then you'll need a totally new unit. Mine stopped working three years ago, at over 300,000 miles... and my poor tranny was taking a hit, until I removed and cleaned up that idle speed motor.
In the mid-late 80s, the dealer where I worked had quite a few throttle bodies with worn shafts which can cause the same symptoms. With the engine off, check for any up/down or side to side movement at the throttle cable lever side of the shaft