Luis de Prat

Car has 146K miles and this problem keeps rearing its ugly head on and off. My father is the regular driver and he doesn't push it at all. Then I get in it and drive the heck out of it and it will begin to hesitate at full throttle. Then it will hesitate at startup, as well.

Also, at startup it sometimes feels like the engine will die out if I give it gas. Feels very weak. After I pass some magic threshold by slowly accelerating and the engine picks up speed and the car drives normally.

Some past history:

Airflow Meter replaced with new unit at 124K
Full belt job and water pump, chain tensioner at 124K
Ignition Control Module replaced at 127K
New alarm control module
Spark plugs replaced about 3K ago
Fuel filter replaced about 3K ago
New OE Oxygen Sensor just replaced
New Bosch 14V voltage regulator just replaced

There is no foul "rotten egg" smell or noises that would indicate a clogged catalytic converter.

Occasionally, there will be a faint gasoline smell in the cabin after the car has sat overnight.

I'm completely at a loss as to where to begin looking for this problem.

TIA

HY M8NC

Throttle position switch? Does it happen the same weather the car is warm or cold?

Luis de Prat

TPS clicks when I push the throttle cable downward. I think the problem appears regardless of temperature, but I noticed that when it was colder out recently it didn't occur for some reason.

Luis de Prat

BUMP. C'mon you Motronic fuel injection gurus -I would appreciate some more input. TIA!

Z-man

Luis - I'd say the TPS as well - does the ticking sound mean it is working properly?

Or - does it seem that the motor is starved of air or fuel? If so, perhaps it's old fuel injectors, or a bad AFM.

Could it possibly be your clutch slipping?

These are only guesses. I know if I haven't driven my 944S2 for a while, it stumbles a little on cold startup, but within a few seconds, it's fine.

Good luck!
-Z-man.

Thom

Hi Luis,

I heard of the exact same problem on another S2 cab near me and it was the idle stabilizer valve. It's a bit of a pain to remove as it's below the intake manifold but good news is that just dismantling it and cleaning it may prove enough.

Good luck !

Luis de Prat

Z-man, the clutch has also been replaced about 6K miles ago.

As for the TPS, as I understand it the way to test it is to move the throttle cable with the engine off and see if it clicks. Mine does click.

Thom, that problem with the idle stabilizer valve sounds very interesting. Anyone have pics of the ISV and it's location?

TIA

Thom

Here you go.

Luis de Prat

Does the manifold need to be removed to take out the ISV?

Thom

Nope, and that's why it's a pain to pull it off.
It's only held by a circular bracket (one can see half the screw on the poor picture I posted).

Riff

Luis-

Check the archives, there was a post on how to pull the ISV out w/o removal of the IM, pictures too!. I used that method and it worked great. Not a lot of fun pulling the ISV out though...

I would think this should only cure the low rpm "wobbles" you have been experienceing. The hesitation at WOT, I have not idea. When mine was gunked up, my idle was wonky, but the car ran fine at WOT.

HTH,

fpena944

How about the fuel pressure regulator and/or fuel damper? Check Clark's Garage for the symptoms associated and the testing process for these parts.

Luis de Prat

I'm not getting black smoke, like I did on my 83 which indeed was the FPR. Could be, but at this point I'm suspecting either a vacuum leak, the ISV or the TPS.

C'mon fellas, any other ideas? My thread isn't as chic as the "new gal in town" but nearing 5K posts I try my best to help when I can!

Tom R.

ISV. I remember reading about it a few years back. a fellow on your side of the pond posted a how to on it some years ago.

Luis de Prat

The idle on the car is quite all right, actually. However, as soon as I get on the throttle it plays russian roulette -either it chokes and nearly comes to a stop, or it doesn't. Very frustrating. I'm sure it's something minor, but it's annoying. Thanks anyway, Tom R.