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Unhappy stalling 924S

Ok here goes!
My 1988 924S 80,000 miles, all original just did the WP belts and rollers this time last year (4000mi ago), will stall almost every time I stop at a light and will sometimes be hard to start when cold (requires cranking for several minutes) it will most of the time start right up again right after it stalls but will take a few minutes on occasion. (toll booths with a large audience! of course)
I have to date replaced: DME relay, fuel filter, plugs, air filter, Idle speed stablizer, reset the TPS, engine temp sensor, and I have in stock and am preparing to change (but if I can avoid installing them I'd rather list them on EBAY!) Reference mark sensor, engine speed sensor, O2 sensor, DME, and AFM.
I am considering possibly a ground problem but they look pretty hard to get to (anybody got any proven methods?) or try swapping out the DME just for a test ride. Personally I feel it is either 1- the O2 sensor as it will run good when it is at a good operating temp say just before the fan kicks on. or 2- the sensors and or the grounds in that area.
Does any one have any suggestions other than take it to a dealer for a DME test plan?
Thanks in advance, and do you think we qualify as a cult?

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Old 10-14-2003, 08:45 PM
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The first thing that you should always check is the connections at the battery and the grounds -- even if they are difficult to get to.

The next thing I would check is the speed and reference sensors. These may have crud on them impeading their ability to "see" the pins and teeth on the flywheel. Also check their clearence; 0.8 mm for the rear one. The front one, the reference sensor, will follow as it's mounted in the same bracket.

Then I would pop the cover on the AFS and see if the wiper has worn through the carbon on the ceramic base. Re-adjust it's location if so.

Then it becomes a series of check/adjust/replace and drive -- a crap shoot.

I would keep the spares if you plan on keeping the car.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 10-15-2003, 12:40 AM
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I'd check out the speed and referenece sensors. In most cases you won't need to replace them, just clean them good as oil and grease can mix with fine metal particles and gunk up the sensors (they're magnetic pick-ups). My car was cranking with no spark at all until I cleaned these up and they're actually not too hard to pull. Just don't move the bracket the bolt to, as the measurement between the sensors and the flywheel must be fairly precise.
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Old 10-15-2003, 12:44 AM
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Have you checked the intake boot for cracks or it may have come off when you where repairing the car. Check for vacuum leaks, here is how I do it,spray carb cleaner aroud the intake,injectors,mass air flow sensor,etc. See if the engine speed goes up if it does that means you have found you leaks fix it and your car should run well again. One more thing the idle speed motor, check that as well With the ignition on you should hear a buzzing sound from this unit if not check votage to it. I have seen these go bad and do just what your car is doing.I see you have repaced this part, but check it just to be sure.I hope this will help you!! e-mail me back if you need any more help GOOD LUCK Tab
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Old 10-15-2003, 12:53 AM
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Thanks guys!
I am going to do the sensors first..as long as I don't move the bracket I shouldn't have to worry about the adjustment unless it is seriously out of wack on it's own?
Anybody have any experience with the Wilk power prom chip? do you think it will improve the driveability of my car and are there any drawbacks other than emissions inspection?
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Old 10-15-2003, 05:42 AM
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my 924 stalled from oxy sensor problems. but i assume yours works ok
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Old 10-15-2003, 06:37 AM
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I have a new O2 sensor and will install it right after I clean all the grounds and clean the reference mark and engine speed sensors.
I hope to get it done tomorrow and will let you know!
Thanks!
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Old 10-15-2003, 07:42 AM
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Tab, I have checked for vacuum leaks and continue (weekly routine! ha-ha) to do so but I am confident that the problem is not a vacuum leak.
I will though take another look at the idle speed stabilizer and I do have a spare.
Socal, I just read Fr Wilk's refurbishing of the AFM and will take that on if the grounds and sensors do not clear up the problem...do you have any comments on the chip (power prom2) that he offers?
This is much more satisfying than dropping it off at the mechanic!
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Old 10-15-2003, 07:50 AM
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Doing one's own maintence is most gratifying especially when it works!

Not really much to these cars. But what is there has to be checked in a proper order. An old oscilliscope helps.

Wilk has a great product. He's done a tremendous amount of work figuring out what will really help and what will not.

I use a propane torch for checking for vacuum leaks. Unlit of course.
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 10-15-2003, 09:41 AM
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I am afraid of propane but thanks! (yer tryin to kill me now?)
and I am going to search ebay for that old ocscilliscope! then they can really call me a mad scientist!
And thanks again, I think I am going to put one of those chips into my spare DME then I can flip flop them back and forth for the old emissions inspection!
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Old 10-15-2003, 09:51 AM
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Actually Wilks has an adaptor board that will let you switch back and forth between performance and smog.

Look for a surplus electronics store around you. Should be abe to get and old oscilliscope for around $50.

There is not enough propane coming out of the torch to do anything like explode. Unlike an engine covered in carb cleaner or either start up spray!

Don't turn the torch on all the way.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 10-15-2003, 10:33 AM
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Alright!
Today I pulled the front sensor, BG and it was fairly clean but...the tan connector seal that goes where the wire meets the sensor itself was cracked and half of it was gone so...the connection to the sensor and wire was exposed to the elements! (that would explain why the stalling was worse in wet and or humid weather, don't think I mentioned that)
I replaced the sensor with a new used one (I am the parts mans dream I have a spare everything, but it is still cheaper than the $119. per hour they get at the competant mechanic) and PROBLEM SOLVED!
I was careful not to do anything else such as clean grounds or change or mess with any of the other sensors to be sure that this was indeed the cause of my troubles...Now I can drive through the tool booths with my head held high!
Thank you all for your advise and expertise!
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Old 10-16-2003, 08:25 AM
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toll booths
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Old 10-16-2003, 08:26 AM
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Whooo Hooo, euro car tinkerers unite!
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Old 10-16-2003, 08:30 AM
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another trick i learned was to coat all electrical connections, plug contacts, fuel injector contacts, EVERYTHING, with dielectric grease and put it all back together... i couldn't believe what a difference this made with the performance and smoothness of my engine.
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Old 10-16-2003, 03:25 PM
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If you have another new sensor replace the other one.

"I love it when a plan comes together!"
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 10-16-2003, 06:19 PM
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I'm glad it worked out for you!!!!
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Old 10-16-2003, 06:38 PM
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I do have another sensor and I will change it, do you think it would tend to be in similar condition?
I also plan to clean all the grounds...do you think it is a good idea to change the negative battery cable and the grounding straps or is a good cleaning with a wire brush alright? and would coating them with a protectant of some type a good idea to prevent corrosion in the future?
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Old 10-16-2003, 07:56 PM
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Yes. Use the second new sensor.

Yes. Clean the battery connections. All of them.

Yes. Drive the car with out fear.

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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 10-16-2003, 11:14 PM
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