gtroth

Hey, thanks for chiming in, Luis. I did read that you had good luck cleaning the AFM connector. Having cleaned mine already, I thought my problem was something else.

Recently, I replaced the Ignition Control Module, and that didn't solve the problem (if I remember it right, you thought the ICM fixed yours for a while, and I bought the part before you figured out that it didn't - I just now finally installed it).

So I cleaned the AFM connector again, more carefully this time (contact cleaner and emery cloth) and had a trouble free day at ~17°F. Then last week I put the car up on stands while I wait for axles so I can't really say yet if this helped me (back on the road today, I think, if UPS comes).

Anyway, thanks again - I'll keep you posted.

Luis de Prat

Actually, the ICM did solve the problem for the most part. Then the airflow meter came out to install the IceShark kit and somehow the connector became contaminated and the car would act up sporadically.

I picked up the tip about the connector from another Rennlister who experienced the same symptoms right after replacing the airflow meter. He just suggested unplugging and reconnecting which worked out well for me.

If you haven't replaced the ICM, definitely do that first, though.

Operator

I just wanted to mention that I got some electrical contact cleaner (in a spray can) and doused the AFM connector with it and, sure enough, I've had a lot less stumbles. It isn't completely gone... but It happens a lot less often. I'de say instead of it happening 80% of every time I drive the car it happens about 10%.. if not less.

So where does the other end of that AFM connector go? Maybe that one needs some contact cleaner too Also did someone say to put vaseline inside the connector to keep it waterproof and fresh? How are your AFM woes gtroth?

gtroth

It's been too warm to tell if recleaning the AFM connector has done anything for me, Operator.

The other end of that harness connects directly to the DME, I think. I've cleaned that too, but not recently.

The idea behind vaseline (or better, dielectric grease) is, as you say, to seal out moisture and prevent oxidation of the contacts. Now, those greases are not electrically conductive, but if the connection has enough contact pressure, the grease will be forced out of the contact point(s) leaving a perfect gas tight seal. I always wonder about what happens if the contact pressure is not enough to force out the grease.

GlenL

Sounds like intermittant elevtrical cut-out of some sort.

I'll go with DME relay. I had one that was temperature sensitive. Known good? I'll need to take off the socks to count the times it's been the "can't be" part that was it.

gtroth

Could be a bad DME relay right out of the box, I suppose. Car was cutting out one day, pulled over, swapped in the new one that's in there now, no effect.

GlenL

That's a pretty good test then.

Lemme switch my vote to crank pick-up wiring.

gtroth

Yeah, electrical connection to the ref/speed sensor might explain it. The waveform looked "right" when I measured it at the DME connector, just a much higher amplitude than the min spec'd in FSM:

ref/speed sensor waveform

so my thinking was that the sensor gap must be adjuted within reason.

I am still kind of wondering if that signal is too high causing some temperture sensitivity (amplitude increses a touch more when real cold, causing some clipping somewhere in the DME circuitry...).

gtroth

12°F this morning and sure enough, on the first hill after the car warmed up it cut out. Just seemed to refuse to push past ~2100rpm this time. Funny thing, though, I down shifted and it pushed right past 3K (roads were too icy to really push it). Restarted after my first errand, and no sign of trouble for the rest of the day, but I guess it was warmer out. I'm about to go look for the firewall connector in the ref/speed sensor circuit. After that, who knows?

Operator

so yours wont kill the car, it just wont go past a certain rpm? that is quite interesting..
and quite different than my problem where the idle would just drop very low from high rpms
but still, both are AFM related most likely? hmm.

gtroth

When under load, say 3500 rpm, it will cut out and drop to say, 2500 rpm, and not exceed that until returns to "normal". When it gets really bad this will cause bucking.
I think your problem is different, Operator. Might be AFM related, but when my idle flopped exactly like that the ISV was defnitely the culprit.

Operator

yea. you might be right.
btw:
ISV = ICV? (idle control valve), right?
part 964 606 160 00

is it truly impossible to replace it without removing the intake?

tkacki

I suspect:
1. AFM - borrow a good one and try.
2. Fuel pump - insuficient output when cold.

Luis de Prat

This is a longshot, but your post about the cold weather reminded me of a hesitation I had a while back in the U.S. with my 83 944. Nobody could find what it was. We replaced the O2 sensor and it disappeared for good.

At any rate, if you haven't changed yours out, your gas mileage can only improve with a new one. Good luck!

gtroth

Operator - on the S it's called the idle stabilizer valve. I think it has finer dynamic control since it is used to set the idle. p/n 944.606.160.00.

Someone said it could be changed w/o removing the intake manifold, but I don't think so (I would never do that, having done the job). Of course, if you pull the IM, there's a laundry list of stuff you should do (IM gasket, injector cleaning, TPS, throttle reseal, vacuum lines (big and small), clean two main grounds, speed/ref sensor check, temp sensor (NTC II) check, dip stick tube seal, - I think that's all.

I ran a thread with some of this:

intake thread

The key to this job on the S is to remove the IM+J-Tube+ISV+Throtte+large vacuum lines as one big assembly. First remove the airbox, AFM (and loan it to me on a very cold day), and dipstick tube (and all the other "obvious" stuff).

tcacki - AFM makes sense to me (wiper track, perhaps). It does behave a bit like the AFM is mis-reporting the load on the engine. The voltage vs angle did match what FRWilk has on his site (his old site, anyway), But hey - it's an intermittent problem. Fuel delivery - never measured that. Fuel pump has 40K miles on it (3 yrs).

Luis - O2 sensor makes some sense too (it's original, has a warm-up time, mechanic suggested it, albeit with some doubt). Time to just do that.

Thanks so much, guys.