911 SC running "flat" and no idle

[jimrs2000]

Its not the relay!!!

I drove the car to the airport this morning with the relay jumpered and it was just fine.

Pulled the jumper whilst I was away.

Re jumpered to drive home and it ran fine, just North of DFW airport I hit major traffic where the roadworks are, the car got hotter and hotter (temp got to about halfway).

Suddenly when I dipped the clutch the revs stayed at 2000rpm and slowly decayed back to 1000rpm, it did this a couple of times.

The all of a sudden the "flat and no idle was back", carried on like that all the way home.

When I got home and pulled the car into the garage I listened, no little whurring sound. I confirmed by pulling the jumper and refitting, still no whurring sound.

It's got to be temperature related, fuel pump relay maybe?

Any idea's much appreciated.

[Bob Kontak]

I wonder if it is the frequency valve?

[Bob Kontak]

Here is what I suggest. If the whirring noise came from the rear it may be the frequency valve. Thing is I don't know what happens if it dies. You can find it behind your idle screw adjustment. About two inches straight back. It is round and has a strap around it and an electrical connection.

When the car is running you can feel it vibrate. It is not real prominent on mine but it is there. With your jumper set up I think it should be on - buzzing without the engine running. (Maybe this is why they put the relay in) Check that out.

The next step may be to disconnect it and see if it replicates the symptoms.

[jimrs2000]

Other than the primer is there a good system description anywhere?

[jimrs2000]

Stanby by whilst I go and get another burnt wrist.....maybe I will try the right hand this time.

[Bob Kontak]

OK - I'll get another Keystone Light - We'll get through this together.

[jimrs2000]

Been out to the car and re-jumpered the relay, still no whurring noise, started the engine and the probelm is still there.

Its still very hot OAT is 100deg heat in the garge even more.

I found the frequency valve and checked the conection...all good, obviously no point in pulling the plug until the engine has cooled down and is running ok.

Left the deck lid open with my garage fan on full blowwing air onto it, have to go and pick my daughter up from band camp in 30 minutes so hopefully it will be cooled down by then.

In the meantime off to the beer fridge....I need something cold for my burnt wrist!!

[jimrs2000]

I the interestes of information gathering I have just swapped out the fuel pump relay....no change.

[Bob Kontak]

Did you burn your wrist? How the heck you burned it on the WUR is beyond me.

[jimrs2000]

EVERYTHING is really hot!!

[Bob Kontak]

I will PM you my phone # if you want me to replicate the jumper test.

[Bob Kontak]

Yep - frequency valve buzzes with the three 87 87b and 30 terminals connected. No key on. Just the juice from the battery via dome light circuit.

Edit - Also started car without relay in - runs like crap - barely when cold - but with time will deliver a little functionality - pathetic, stinky, backfiring functionality - but would allow you to limp home. Now - given the price of the frequency valve - what could cause it to fail other than the frequency valve itself?

[jimrs2000]

Bob, it was great talking to you, you may have gathered from my accent that I am from east Texas originally......WAY East Texas!!

Interesting that your car ran like crap without the relay and mine runs good until the problem occours.......

There are two temperature sensors in the system, what do they do? I am particularly interested in the 35deg C one. Does it change the output from the 02 control box to the frequency valve?

By the way I have not looked at the price of new frequency valve, do I need my financial advisor to take a look?

[Bob Kontak]

I worked for BP for 23 years. I have heard that accent before. I am thinking, like, beyond Louisiana way east.

Will check temp sensor function and revert.

Freq valve is pushing $500.

[jimrs2000]

If I can find where the 35 deg temp sensor is I can bypass it and see if that cures the fault.

Aircraft engineer myself, now working for Rolls-Royce (past 22 yrs).

Suddenly troubleshooting airplanes seems so easy!!

[Bob Kontak]

Check out page 19 in this pdf parts catalog. Part 37a may be the one you are looking for.

http://www.porsche.com/all/media/pdf/originalparts/usa/911_USA_78_83_KATALOG.PDF

I have been trying to eliminate the sensors I can see by using the wiring diagram that shows the wire colors and some detailed pics I took last year of my engine when out. The one I cannot see from my pics (wire colors) is the temp sensor that is 37a which screws into the oil lid - part number 37 - which will be hell to get to.

I also cannot find what the function of the 35C sensor is although it feeds into the Control unit via the green and yellow wire (which I cant see)

The 15 degree sensor is the one on the passenger side chain housing. The thermo-time switch is on the drivers side chain housing. The oil pressure (can looking thing) sensor is next to an oil temp switch that does not feed the control unit.

There may be a way to bypass it without getting to the sensor - but that is for another day - for me at least. :-)

[jimrs2000]

I am not going to use the car again today, If I get time I will reasearch the operation and logic of the 02 control computor.

[Groesbeck Hurricane]

What CDI do you have? Bosch, permatune(JUNK), or something else.

This issue sounds related to temperatures in my minds eye.


Ever hear of Carmona, Texas?

[jimrs2000]

I have a permatune through nececaty (Bosh broke and it was all I could find short notice).

Not heard of Carmona but I have only lived here 3 years. Where abouts is it?

Plan for tonight is to drive the car until it fails and then bypass the temerature sensors to see if that works.

[jimrs2000]

Ooh really bad spelling ....sorry.