John Speake

I think you have to be a paid up Rennlist member to be able to add signature ?

Randy V

This.

worf928

Idle switch contact? If the 928 idles normally-ish durning the first few minutes after cold start, then idles really low then it may be due to the idle contact not closing (defective or cable issue.)

I can't type-up more instructions, I've been under a 928 all day and my hands are shot. So, someone else please post on checking the idle contact.

Last, do what Sean suggests : disco the battery for a few minutes then see what happens.

landsharklady

Car is constantly idling st around 625rpm in park or neutral.
It starts, finds it's idle around 625 and stays steady there.
It drops down to around 625 when we pull up at lights etc.

With the old MAF it was going all over the place, there was no stability at all at low rpm and it would cut out.

Now, low rpm but steady and performance is very good.

There is no problem (so far, fingers crossed!) With the lower idle,.just strange.
No one seems to have any idea why it does this now.

The car had obviously been running with a declining maf for a long time, maybe got some reason it just runs at low rpm when it has a good maf?

Randy V

Did you try disconnecting the battery?

Hilton

If you're reading the rpm off the tacho, then it may well be 675rpm and the gauge is just wrong. e.g. the needle has slipped a little over the last 24 years of vibration.

The easiest way to verify the rpm correctly is via the electronic signal (can be read from the diagnostic connector by the passenger seat under the cover with the switch for the hatch - pin 14). Your mechanic will certainly have a multimeter capable of reading rpm's - the signal is the same as a 4-cylinder engine (its based off one ignition bank).

If its bothering you, it should be the work of about 3 minutes for your mechanic undo the thumb screws, stick a probe into pin 14 (numbers are embossed by the holes) and get a reading.

Just go drive and enjoy the car until it breaks again.

landsharklady

That's what I'm thinking, it's working, let's leave it at that! Yes, battery was disconnected.
can clearly hear the difference in the rpm, and it's a lower rpm than it was a week ago it's def let, but if it ain't broke...

Randy V

Sounds like it's not gonna get any better than that.

Dean_Fuller

Can she tighten the throttle cable just a tad to take slack out and raise idle ??? I know this is not really the way to do it but it sounds like we are talking very little extra rpm needed.

TheoJ

Hi,
a MAF that produces an output out of spec (flow related output voltage) may either cause the idle RPM to be very high or very low depending on what the deviation is. And wrongly acquired LH data confuses the LH. As someone already mentioned, unplug the LH for a minute, reconnect, and let it adapt.
regards
Theo Jenniskens
1992 928 GTS

John Speake

The MAF calibration is in spec.

Don't tighten the throttle cable or the closed throttle switch won't close and the idle control system won't be activated.