Can anyone help my sick car?

[twin plugged targa]

If this is beginning to bore you guys, just think what it is doing for me!
I am just trying to sell the damn thing, and everything is starting to fall apart around me!
After replacing the coil- no difference, no start.
Replaced the head temp. sensor and the car burst to life!. Glee, joy ...... short lived!.(I ran the car for only a 10 minute test and did not drive it anywhere as it was still in 'bits'.
I put the rest of the car back together yesterday, finishing off by polishing off those oily hand prints!.
'Happy as a pig in s@!t' all cleaned up I descided to take her for a test run!.
3-4 miles out of town she..... yes you guessed! DIED!
She would start and idle, but when put a bit of throttle on she 'bogged' and died. After letting her sit and cool i managed to limp home. She stalled another 4 times on the way.
It now seems like a time/temperature thing!?
I am running out of ideas!
I am guilty of not trying everything you all have said, but my next step is to clean every ground strap I can find. Also to test the fuel pump which was new 6 months ago!.
Maybe the fuel pump has worn prematurely and is over heating?.
What else could be effected by time/heat?
Any help would be really appreciated.
Thanks again Ben
PS spoke to an enthusiast in the parking lot who has the same car (year/model/mileage) and has only replaced an alternator and a few tires in 10 years!
Guess that answers may question as to 911 reliability as he said 'most reliable car I have ever had!!!!'.
Oh well......

[vjd3]

It's the throttle switch ... see the "lurching cab" thread. I had the same problem with my 88 Carrera. Switch is about $65 and an hour to replace. Your DME thinks the throttle is always closed when the car is warmed up and it won't allow you to rev the car between 900 and 3000 rpms. See if you can goose it up over 3500 or so (it takes a lot of trying and stalling), it should accept throttle and rev normally. You can drive it that way if you're stranded by not letting it rev below 3000 or so, but it's hell on your clutch.

Vic
88 Carrera

[This message has been edited by vjd3 (edited 06-03-2001).]

[twin plugged targa]

Heh Vic,
You could be right.
But I have just done the throttle switch tests and it passed?
I will not rule it out and if I still have no joy by the end of the day I will order one from Pelican Parts.
Esp. as it is fairly cheap- at this rate I am close to replacing the whole electrical sysytem!
Thanks again

[vjd3]

It is usually an intermittent problem, mine would come and go, it might work fine while you're testing it and then let go later. It was a ***** to diagnose because, predictably, it wouldn't do it at the shop I normally used, and I wasn't about to start throwing money taking stabs in the dark at it. I finally found a mechanic who had seen the problem before, we replaced the switch and it never did it again.

If you have a friend with an 86, maybe you can swap his out and see if your problem doesn't go away (or move to his car).

Vic
88 Carrera

[This message has been edited by vjd3 (edited 06-03-2001).]

[JGT]

Sorry to here your problems!Try this.At the coil look at your postive and negitive connectors on the wires.If you have aluminum connectors,this may be where the fault lies.Over time aluminum oxidizes(a natural process) forming a nonconductive film ,copper does the same thing!This means the crimped joint may look fine,but nature may be disconnecting your Porsche.Combine this with the differances in material expanion rates and the high underhood temperatures may explain the timing of your stalling.Any aluminum to copper joint should be cleaned and silver soldiered for a positive connection.Or better yet use brass connectors if available.Good Luck

[twin plugged targa]

Thanks JGT, I did wire brush the terminals but maybe I should replace them altogether.

Vic, did your throttle switch problem happen intermittantly or after warm-up.
My problem seems apparent only after warm up- cold she's fine but warm - forget it!
I will change out this part and after that I reckon it could be the DME.
rgds Ben

[Jorgeman]

Ragtop--I hesitate to believe in two different problems occurring at the same time. Go back to what fixed it (temporarily)-- the temp sensor and start there.
1) Possibly a faulty sensor
2) Check the electrical attachment of BOTH wires--including the ground you are now using.
3) The original sensor probably didn't fail, they just act that way because they depended on the screw threads to provide a ground but the matals being dis-similar, would corrode ruining the ground.
4) Hopefully you didn't use teflon tape or loctite on the threads which would act as a heat insulator.
5) Do a search on these boards--I seem to remember someone posting resistance readings for the sensor.
It's not impossible there is something else wrong but my experience has been that we PUT more bugs on machinery by chasing too many possibilities at one time. Your description still sounds like temp sensor.

George 86T

[vjd3]

It always happened when the motor was warmed up, my guess is the fuel cutoff function does not occur until the engine reaches operating temperature. I would definitely try to get the problem happening and see if it will accept throttle over 3000 rpm, that was the telltale. I just read an article about a 944 in Upfixin' that had the exact same symptoms and solution.

Let us know what you figure out.

Vic
88 Carrera

[twin plugged targa]

Thanks Vic,
I did the Bentleys tests and the throttle switch and harness came up as working but that is when the engine is off and temp. cool!.
I will order a switch on Monday and hopefully that will be a cheaper fix than the DME which is next on the list!
Will let you know how it turns out!
Thanks again for the comeback!
rgds Ben

[DRD]

Hey, If you need a DME I have a rebuilt unit with a warranty from vertex, bought it 1 month ago, and have never used it, I ended up fixing the problem after I bought the DME
DRD
Darren

[twin plugged targa]

Heh Darren,
What was your problem? similar to mine?
I will contact you if I need a DME and maybe we can do business.
I thought the DME's from Vertex were in exchange for your old unit?
rgds Ben

[Ned, NYNA 11]

Ben,
I had an intermittent in my 87, caused by the DME relay having a bad connection. This one is under the driver's seat and can be unplugged easily.
Ned Monaghan

[twin plugged targa]

Thanks Ned, but I put a brand new DME relay in this afternoon- I always carry one as a spare!.
No improvement.
But thanks for the thought
rgds Ben

[DRD]

Ben, I had a problem with a intermittant connection from the flywhell speed sensor to the DME. Somtimes she wouldn't fire up after setting. I have allot of experience with these DME systems. From the sounds of your problems, I would change the throttle postion switch. If that dosent fix it ,change out the 2 flywheel sensors and that should fix the problem. Basically, you need flywhell postion sensors and throttle postion sensors to make her run at a min. Sounds like the heat is breaking down a device.
Good luck!
DRD
Darren

[Roland Kunz]

Hello

Fuelpumps run in fuel and get cooled by that. As long they don´t run dry or someone blocks them off fuel they run endlessly.

After some 500 Porsches I never had seen that the factory used undersized or even cheap crimp on connectors. Some of them are even silver coatet.

But time take his tool and hell 15 Years, 99 % of car population is recycled into new Neons or other SUVers. Porsche used very good cooper wires but they do oxide too.

Generally good tips another is to check for vacuum loses especialy to the fuelrail valves ( Broken rubber Y ).

TDC
Position and speed sensors are interchangable and can be messured with a good full electronic multimeter ( Fluke / Bosch ). They should be clean and have 0,8 mm distance from the flywheel teeth.

Sometimes the TDC position mark on the flywheel gets "unmagnetic". Never had that but it was a rumor some years ago.

Grüsse

[twin plugged targa]

WOW! My post threads are now showing again (thanks if you did something wayne!)
New advice, great thanks guys thought you had given up on me!
The 2 flywheel sensors were replaced about 8 months ago by Vertex (they broke the plugs!)
I am going to check the new head temp sensor and then if that is okay then go for the new throttle switch (even though the Bentleys tests show working!)
At this point i would love to take it into a garage as I am running out of ideas and time (even I have to work sometimes )
But the main problem there is that there are no good garages up here in Long Island (Hamptons) unless someone can advise me otherwise?
Keep those suggestion coming please, and again, thanks!
rgds Ben

[twin plugged targa]

Update:
Lighthorse engineering of Hampton Bays (Blair) had a spare compatable ECU (DME) available for testing.
I ran the car with original ECU for exactly 25 minutes at standstill, with the only symptom being the revs fluctuating or 'hunting' from 1000-1200rpm occaisionally for a minute or so then returning to normal for a few minutes and back and forth!.
Then on the 26th minute (ambient temp. low 70's F.)
The engine died, would restart and die (with pre ignition)
At this point I changed over the ECU - with exactly the same symptoms, tried to run dow the road and she would die!.
Limped back to the parking lot!.
What to do next?
I beleive that if the throttle switch was bad it would not run cold, after all it is mainly a reostat, no?
comments appreciated!
rgds Ben


[This message has been edited by 86ragtop (edited 06-05-2001).]

[DRD]

Ben, great trouble shooting. Ok, can you hear the fuel pump run after you try to restart the engine. You might hang a test gauge off the test port drive it around and make it die, go and try to restart it and see if it has fuel pressure. Ther is also a small round relay that runs the fuel pump, could be bad.
The DME wants to see, tdc and position sensors, head temp sensor, throttle sensor, and afm.
One outhe r thing, is after she dies, test the throttle postion sensor? Maybe the heat is getting to it? Another thing is the ignition switch goes bad too.
DRD
Darren

[nhromyak]

If this was the problem, I don't think it would run when cold, but what about the vacuum based fuel-pressure regulator? Does this have the vacuum line properly attached?

Just a thought...

------------------
Nick Hromyak
'85 Carrera 7 & 9 Fuchs
Havin' Fun in Sacramento

[Marshall Reddin]

Ben, measure your fuel pressure, first when the engine is cold, again when the symptoms appear. Probably best to leave the guage connected to avoid spilling fuel on a hot muffler. I agree with the earlier post - fuel pumps rarely ever fail. Relays fail frequently, and possibly the regulator could fail.
Marshall