darren1031

Ok, engine up to temp. 95F ambient temps, A/C on, coolant temp normal.
Engine shut down for about an hour. Car starts, idles horrible..like 400rpm.
I give it gas to 1000 rpm to keep it running. Take foot off accelerator, engine
dies. Restarts, but if I dont keep giving it gas, engine dies. The AFM is new.
The ISV is new. Started the car the next morning, engine ran and idled fine.
I have normal drivability at speed. So, what's wrong?

DME temp sensor II?
O2 sensor?

I have never replaced the O2 sensor and I have had the car a looong time.

Any other ideas? I'm baffled.

Darren
Tuscaloosa, AL

krahmlow

You can test both of those sensors without taking too much apart. Clark's garage has the process written up. Look under "engine troubleshooting" or something like that. If you haven't gone through the ignition system, you might want to do that, if only for peace of mind.

Peckster

Check to see if the air adjustment screw is still in the top of the throttle body.

If it only does it during warm restarts it could be vapor lock, caused by dirty injectors or a number of other things.

gtroth

...not on the 'S'.

If you can get your hands on a factory service manual, there's a good DME Diagnosis and Trouble Shooting Guide section that's real useful.

I don't think the O2 sensor will muck up the idle that bad, but I could be wrong. I'd probably double check the AFM connection, check the TPS, and definitely check for big vacuum leaks.

PeteL

Fuel Pressure Regulator.

Calmchaos

Fixed my no idle

PeteL

FPR fixes pretty much everything!

darren1031

My FPR is new..about 1 yr old. Still have the original dampner though, but
I doubt that's the problem. I'm thinking the DME temp sensor or the O2
sensor. Got parts on the way.

Darren
1987 944S
Tuscaloosa, AL

darren1031

Update: I've replaced the DME temp sensor and the O2 sensor. Still, the engine won't idle. This doesn't happen
all the time. In fact, it has only happened 3 times in the
last month. Seems to happen when engine is at temp and
then shut off. Start it 15 mins later and it won't idle. This
is what I've replaced:

AFM: 11/05
ISV: 12/04
FPR: 12/04
O2: 6/06
DME temp: 6/06

Had a valve job last June due to the failure of the self-tensioner to maintain proper tension on timing belt.

When it doesnt want to hold idle, it looks like it's running on
3 cylinders. The ISV attempts to maintain idle, but can't.

I wonder if I have a failing injector. Don't know what else to check.

Darren
Tuscaloosa, AL

AZS2

I would have voted for the FPR too. Even though its pretty new.... Just pull the vacuum line off the FPR and make sure its not leaking fuel into the vacuum system causing a rich condition.

Yours is probably good but.... This is what happened to mine. It would only do it after the car was run. Otherwise if the car sat all day or night, the fuel would evaporate and the car would idle fine for a while.