I hope you remember the story. (If not, you can refresh your memory below.) You will NOT believe what the cause of the problem was! You know those two little screws that attach the ignition module to the distributor, they take a Torx wrench to tighten/loosen? The one closest to my thermostat housing had worked its way lose. How, why I don't know. While hunting/searching, again, all my vacuum lines for leaks, I just happened to notice the little screw lying in the [screw's] deep mounting hole in the ignition module. The screw was blocked from completely falling out because the end of it would bump into the thermostat housing. I twisted the distributor around and tightened the screw, not knowing what effect it would have on the car. Then took the car for a little test drive afterwards and the idle problem didn't appear, and it has been a couple weeks now and the car has run perfectly -- not a single hiccup in the idle. Just a coincidence? At this point, I'd bet the house it's not.
Okay, now who's going to claim these screws being loose was their second guess? :-)
Patrick
Patient:
>
> 1993 Cobra/125,000 miles -- stock except: shorty headers, advanced
> timing, 73mm C&L mass-air meter and an A9L processor.
>
> This combo ran solid for a number of years and the symptoms suddenly
> -- no mods or changes were made -- just appeared.
>
> The symptoms have gone on now for about 1 1/2 years.
>
> The frequency of the symptoms has slowly increased from maybe once a
> week to almost every day. But despite the symptoms, the car performs
> well without any popping, missing, stalling, gassy smells, or smoking. > -----
>
> Symptoms:
>
> Reved-up idle. Sometimes. Some days, the car will run fine all day
> long, or for a couple days. Other days, the reved-up idle will
> continue to happen.
>
> Idle speed varies, but generally sticks -- doesn't roll -- somewhere
> between 1600-2200 rpms. Never goes above 2200.
>
> Generally, I get the reved-up idle a few minutes -- 3-4 minutes --
> after a cold start AND after I dip into the throttle a little bit. >
> But frequently I get the reved-up idle when/after the motor is fully > warmed up.
>
> Miles and miles of driving -- 20-30 -- even at highway speeds, often,
> won't alter the reved-up idle.
>
> Running the car hard, even really hard, doesn't change the idle (if
> anything, it often makes it go higher up in the 1600-2200 range). >
> Normally, running the car hard will trigger the reved-up idle.
> -----
>
> Complications:
>
> Shutting the car off and restarting _always_ fixes the idle, at least > for a while.
>
> No codes have _ever_ popped up in the computer.
>
> Sometimes the idle will just fix itself while driving.
>
> And a few times _while reved up_ I've had it just fall to the normal
> idle speed and stay there. And a few times, after falling to a normal
> idle, I've had it return to the reved-up idle -- like someone is
> controlling it by remote.
>
> A scan tool was run once while the idle was reved up and, for some
> unknown reason, the reved-up idle didn't return for nearly 4
> months. Also, a few minutes _after_ the [scan] tool was
> _unplugged_, the idle dropped to normal and then a few minutes later
> it reved back up. Coincidence? My mechanic, and he's extremely good,
> was at a loss, but thought the processor might have some issues.
> (Note: My mechanic drive my car home that night and the car ran
> PERFECT for him. It's about a 40-mile loop for him to drive to and > from work.)
> -----
>
> Recent developments:
>
> A few weeks ago, I noticed on two occasions, a missing while driving/
> cruising at highway speeds. The missing has since gone away.
>
> Also, after a cold start leaving work one day, a few weeks ago, the
> idle went below the normal idle speed and the car acted like it was
> going to stall. After a few minutes of driving the problem went away
> and hasn't returned since.
> -----
>
> Treatments used so far, in this sequence:
>
> 1) Fuel filter
>
> 2) New TPS
>
> 3) New Air-Idle Control valve
>
> 4) New Mass-Air sensor (the actual sensor unit in the mass-air meter) >
> 5) New A9L Processor
>
> Each treatment was used independently, but nothing has helped/worked. > -----
>
> Besides a gun, does anyone know of a cure?
>
> Patrick