2005hemi

I have a 1990 targa with a strange problem. I put the car away for the winter and when I started using it,a few months later,I ran into the folowing problem: If I am driving in 4th or 5th gear all of a sudden It appears that the fuel was shut off. If I push the gas pedal to the floor and keep it there it will either be non responsive or stumble and then rev up. If I down shift when it happens and rev it, it comes right back. I brought it to my Porsche guy and he drove it for 4 days and he could not replicate the problem. It happens to me every time.So far I replaced the DME relay, and fuel filter, I checked all the connections to the computer under the seat, both coil connections and all connections on the motor.Any ideas? I could really use the help. I have used about 6 tanks of fuel since the problem started. thanks,

Mark

Colin 90 C2

Sounds like it may be an intermittent flywheel speed reference sensor . I believe that they may be a problem with the contacts corroding on the connector that is located behind and below the heater fan.

You can try cleaning the contacts and see if that resolves the problem.
You will need to remove the heater fan in order to get to the connector.

2005hemi

Colin,
Thanks for the info, I am going to replace the DME Relay again. It seems that my mechanic installed a used one. I am off to Porsche to get a new one. If that doesn't fix it, I will check the contacts on the sensor. Is that sensor normally replaced when a new clutch is installed? I had the clutch redone just before the winter.

Mark

Adrian

Dear Mark,
No the flywheel sensor is not replaced unless it is broken. However clutch replacements can see them get damaged. The problems pointed out by Colin are genuine and growing as the 964s age.
Unfortunately you do not share with us where you are from and the tpye of 1990 Targa you have. Every piece of information can be very valuable in trying to help troubleshoot your problems. There are ROW and US versions and slightly different variations between manual and tiptronic.
An O2 sensor full of water can also cause your problems. As can a damaged O2 sensor connector.
Ciao,
Adrian
964C4

2005hemi

Adrian,
Sorry for the lack of info.I am located in NY the car is a 1990 C2 targa , it has 101k on the odometer. I purchased it with 97 on it. I just came back from the dealer and installed the 993 series DME relay, no good. Just diving the car, this is what happens.running throught the gears 1,2,3,4th up to 6,000 it runs perfect. once I am crusing in 4th oi 5th and I hit the gas, it will bog down(like no gas ) If I back off the gas and punch it one or twon more times it will usually rev up. When this happens and I downshift to 3rd, the revs come up and it is ok. I accelerate and shift to 4th o0r 5th , let off the gas then hit it again ,it happens as before. I appricate the help


Mark

Adrian

Dear Mark,
I could send you around in circles. Could be a vacuum leak, could be a failed or intermittant reasonance valve. Could be a failed or intermittant wide open throttle switch.
Yours might be a candidate for the Hammer to read out any fault codes. This might be the quickest way.
Ciao,
Adrian
964C4

2005hemi

Adrian,
Thanks, I am going to see if my local dealer has a Hammer. I will follow up after they check it. Again thanks for your assistance
Mark

Colin 90 C2

Mark, if you have a hour to spare, I would just check that flywheel sensor connector. If the engine was dropped to replace the clutch, then the connection was probably undone. It is possible to have the connector look like it is together and not be electriaclly connected or intermittently connected.

Don't ask me how I know.

I was experiencing similar symptoms until the connector finally came apart electrically(but still looked mechanically together), and the engine died and would not restart. After a few minutes of troubleshooting (after a phone call to a buddy and a tow home and some advice from the local p-car dealer mechanic), the connector was found, reconnected and perfect running since. That was about 6,000 miles ago, but it seemed like yesterday.

Good luck,
Colin

2005hemi

Anyone have a picture of the flywheel speed sensor? I am going crazy trying to fix this. I put a new 993 DME Relay in today and no change, The car only runs good under full throtle.
thanks
Mark

mark964

Here ya go ...

Adrian

Dear Mark,
If you are going to try and fix these things DIY you need information at hand. It is not possible to lead somebody through complex problems like this unless you have some reference material.
I naturally recommend you purchase my book which provides much of the detail you will need for troubleshooting and give you the materials to work out problems like this.
The explanation you give in your latest post about "only runs properly at full throttle" is a little different to your first posts.
Only running properly at full throttle suggests;
O2 sensor problem.
Airflow sensor problem.
My advice is to take off the airbox and check for oil contamination of the air intake system.
The reason I say this is because when the WOT microswitch is made the O2 sensor input is ignored and the airflow sensor input is maximum and any changes to the signal are ignored.
Ciao,
Adrian
964C4

Mark Brook

Dear Mark and Adrian,
I had this problem last summer, and my mechanich fitted a new O2 sensor, then an Air Flow Meter, and re connected the headlight leveller pipes. Seemed to sort it out, until my latest high revving episode. (seperate thread 'stalling')

Cheers,

Mark 90C2

Adrian

Dear Mark,
Headlight adjusting system disconnected = vacuum leak = not good running engine.
The problem of replacing all of these parts though is that you are well out of pocket and you do not know the actual cause of the problem.
In the trade this is called "Shotgunning".
With these problems that could be a a wide ranging number of things I advise personal troubleshooting (DIY) if you have the expertise starting cheap and working towards expensive. If you have to use a mechanic I recommend you ensure a Hammer read out first and record the fault codes yourself. Then you can do some research and at least guide the mechanic to avoid massive bills caused by the replacement of perfectly serviceable parts.
I think I wrote a book about this
Ciao,
Adrian
964C4

2005hemi

It is FIXED!!!! I brought my Targa to my local Porsche guy. He hit it with a Hammer(Bosch) We determined that it was an electrical issue, it seems that the connector to the air flow meter was the issue. I was told that on the early cars Porsche plastic tie wrapped it . Well we cut the tiewrap and moved the cable and cleaned the connection and it runs great. I want to thank all of you with your help.


Mark

ian c - u.k

£50.00 = BOOK , will last forever
£50.00 = MECHANICS FEES , only lasts an hour

i'm no financial advisor , but i'd say its a solid investment !!