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Old 01-28-2011, 05:30 PM   #1
x2nervisx
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Default Car stalls when I press on the gas pedal

I have an 83 944 that I just bought as a project. I can get it started after a few tries and it idles pretty good. As soon as I try to rev the engine, even just a little bit, it stalls out. Any ideas?
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Old 01-28-2011, 05:32 PM   #2
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Clogged Fuel filter, clogged injectors, bad throttle position switch (although less likely, but could be)..

Also check the air flow sensor...

Check out the shop manual section of http://www.clarks-garage.com/

lots of little tips and hints on troubleshooting...
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Old 01-28-2011, 05:37 PM   #3
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Could be any number of things...vacuum leak is the first and simplest thing that comes to mind. You've indicated the car is a project. Had it been sitting a while before you acquired it? Duration of "non-active" time might dictate a thorough check of all things rubber, among other seemingly small projects.

Good luck with the first of your gremlin hunts!
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Old 01-28-2011, 05:58 PM   #4
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I would check to see if AFM is stuck open. If that looks okay then move onto something else. I would pull the plugs see if they are wet or anything out of place.
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Old 01-28-2011, 06:00 PM   #5
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Major vac leak comes to mind first but your TPS could be sticking in the idle position. My money is on vac leak.
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Old 01-28-2011, 06:58 PM   #6
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Where is the tps located?
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Old 01-28-2011, 07:00 PM   #7
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And yes the car was sitting for about a year or so unused before I got it last week. Was probably hardly used since the last registration says 2001 on the windshield.
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Old 01-28-2011, 08:07 PM   #8
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It is a black box mounted directly under the throttle body. It has 2 micro switches inside it. One makes contact at idle. The other makes contact at full throttle. Any partial position between idle and full and both switches should be in the open position. You can check it with an ohm meter at the contacts.
If you search, there should be a TPS test procedure somewhere with pics. The NA TPS (that you have) operates different than the turbo, just FYI.

When the TPS is in the idle position, the computer runs a 2D map that doesn't have any fuel values over x number of RPMs. 1500? I think.

All that aside, I still think its a vac leak. Check the metal vac pipe that connects to the bottom of the rubber J boot. That part of the boot likes to rip.
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Old 01-28-2011, 11:57 PM   #9
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make sure afm is still attached to intake
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Old 01-29-2011, 12:17 AM   #10
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Quote:
Originally Posted by Travis - sflraver View Post
It is a black box mounted directly under the throttle body. It has 2 micro switches inside it. One makes contact at idle. The other makes contact at full throttle. Any partial position between idle and full and both switches should be in the open position. You can check it with an ohm meter at the contacts.
If you search, there should be a TPS test procedure somewhere with pics. The NA TPS (that you have) operates different than the turbo, just FYI.

When the TPS is in the idle position, the computer runs a 2D map that doesn't have any fuel values over x number of RPMs. 1500? I think.

All that aside, I still think its a vac leak. Check the metal vac pipe that connects to the bottom of the rubber J boot. That part of the boot likes to rip.
TPS test procedure is in the link I provided, under Garage Shop Manual look for Throttle Position Sensor...

IMHO it would have to be one hell of a vacuum leak to cause the engine to die with any application of throttle, but I suppose it is possible... but more likely the bad gas has varnished over the last decade in the tank.... clogging the fuel filter, injectors and such.... the TPS is stuck at idle, or the AFM is not registering anything above idle airflow!

Vacuum leaks I have encountered cause poor idle, and stumbles off idle (even though it continues to run off idle)
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Old 01-29-2011, 12:36 AM   #11
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I forgot to tighten the clamp that holds the AFM onto the J boot once. It wiggled off but only at the bottom leaving the top visually on. Took me all of an hour to find it.
The car would idle just fine but as soon as I gave it gas, it would die. It would lean out because the AFM was being bypassed by the huge vac leak just ahead of it.

Specifically, thats why I think its a vac leak.
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Old 01-29-2011, 01:29 AM   #12
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Is there a procedure to clean out the afm?
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Old 01-29-2011, 09:17 AM   #13
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Air Flow Meter (AFM) information, click on AFM in the side bar
http://the944.com/
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Old 01-29-2011, 09:32 AM   #14
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Quote:
Originally Posted by Travis - sflraver View Post
I forgot to tighten the clamp that holds the AFM onto the J boot once. It wiggled off but only at the bottom leaving the top visually on. Took me all of an hour to find it.
The car would idle just fine but as soon as I gave it gas, it would die. It would lean out because the AFM was being bypassed by the huge vac leak just ahead of it.

Specifically, thats why I think its a vac leak.
me too, I felt so stupid for not noticing it
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Old 01-29-2011, 11:33 AM   #15
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HUH, learn something new every day.. as many times I have had the AFM off, have never done that one...
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Old 01-29-2011, 11:33 AM
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