TFI?

I cured this problem, in part, for a while but it is back again...

Symptoms are pretty classic.
I have not pulled codes since it came back but, will do it today. Car starts OK, no high idle at all just runs. Then RPM will begin doing this up and down deal, rise a bit, then fall a bit, then a little higher and a little lower each time. The idle drops a bit first I believe, then the computer seems like it just can't keep up with the RPM fluctuations and and lags behing with it's corrections, a little too late unfortunately. It seems this way anyhow.

Idle falls to 800 from 1000 for instance, then computer over compensates and it rises beyond 1000 to 1200 or so to correct, then seems to realize that is too high so it lets it drop, but it goes too far, farther than before and drops to 700, realizes it and this time will go even higher, say 1400 or so, then falls again to maybe 600 this time and on and on going higher and lower until it enevitably falls "too" low and dies.

It will do this with the heater off/no AC clutching affecting it or not. When off, it only prolongs the up/down cycling, but it still dies..

I replaced the distributer rather than mess with the PIP only, then the TFI. It was cured... for a while. I believe it is one or the other, or both again, and wish I had the money to buy a half a dozen TFI modules so when it does idle again I can then check the other modules to find out if any of the others are defective.

Even when the thing does idle correctly, stable and such, I have never had either of my 88 TC's run on high idle when cold outside... and this is VERY frustrating because they will always run a little lower RPM from added friction even running Mobile synthetic, and any little hickup or engine load can cause idle to fall just enough for them to occasionally die. Like the fan cycling on. It doesn't seem like I should have to raise the base idle as they both already run at ~900-1100 RPM. I would expect to see 1500+ RPM for a minute or so then see it scale back but this just never happens. It's just something I don't have to deal with with other rigs. Mainly it is because the wife has to put up with it, that it irritates me. It is just not dependable, and I know it has to be something simple.

The IAC has been cleaned and I see no reason to replace it but feel like throwing a bunch of new parts at it to see what happens.

Anything I can do to get this to run higher on start up?

Not likely to be the TFI. Check the TPI voltage at idle. See the tech page for a procedure. Wandering idle is likely caused by bad TPI adjustment.

Going to check it. Thanks Robert

Everything seems to be running a lot smoother so far after simply adjusting the old TPS and curb idle.

Car wouldn't run with IAC unplugged so one turn in on the idle screw and then it did. Set idle to 750-800 rpm. The initial TPS voltage was a bit over 1v, about 1.1v. It ran up to about 1.2v or so when raising the idle a bit more so I set it back down to .94.... with the scews tight.

Plugged in the IAC and idle jumped to 1500 and slowly began fallig to 1000rpm, took about 30 seconds to a 1 minute to come down and stabilize.

The car starts up when cold (about 20 deg F this AM) at around 1200 rpm now, slightly higher than normally does but idles smoother, like one would expect their car to.

I would think it should idle a bit higher still, but maybe someone else knows for sure what the high idle speed is suppose to be?

I noticed for the first time that my AC and fan are cycling when in defrost mode, when engine is at operating temp only. It is not in Auto mode, only the fan is set, floor or pannel do not activate the AC and fan, but any combo including defrost will? And I had the temp set at 90* too. Doesn't make sense to me.

I was concerned it would try to run the AC and fan when cold on start up using defrost but this morning it did not, so it must only do it after entering open loop, I guess.

Can't really say what 20 deg F would do, but 1200 rpm high idle for a short time, then settling back to 900-1000 when warm is fine.
This sounds good to me.

The AC cycles when any defrost mode is used = normal

I think the EATC system has sensor to keep fan off until a certain coolant temp is reached to keep from blowing cold air (in winter).

Originally posted by Pete D:
The AC cycles when any defrost mode is used = normal

I think the EATC system has sensor to keep fan off until a certain coolant temp is reached to keep from blowing cold air (in winter).

You can take the qualifier out of that statement Pete, as your info is correct regarding the fan not coming on with cold coolant!!
Mike C

Yes, Pete, you are 100% correct. BTW- mine has the same type of idle at that temp range until the TC gets warm. I wouldn't worry, sounds fine to me. Amazing what the TPS can do, huh?

James

It has been idling initially between 1200-1300 so far. It is very stable and seems to stay up high to warm up quickly for plenty of time too. I have yet to try it with the heater in auto mode because although the heater fan coming on is delayed until temp is higher, the ac and fan cycles from the moment it is started, a major idle disruption. When mine is not in auto mode and instead the fan is on manual high setting, the heater fan will run regaurdless of coolant temp, but the load on the engine is consistant, never disrupting idle speed.

Now I see that the idle runs stable without the AC disruption, I'll have to see how it handles the AC in auto mode.

It has been very nice to be able to start the car up and walk away from it knowing it will be running and warm when I come back out minutes later. The embarrasing PITA idle now leaves me smilin.