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1987 944 Turbo poor running while cold

My 87 951 has started to run poorly for the first few minutes now that outdoor temperatures are in the low 30s.
I was wondering if this car has a warm-up regulator, or would the fuel pressure regulator be the cause?

I am also trying to fix the cargo cover. My car has the older style cover with a flat metal end on the passenger's side and a pin at the other end.
The plastic pieces at the end of the tube that holds the cover broke and replacements are not available.
Would there be a cover from a VW or newer Porsche that can be modified or the end pieces used to fix this one?

Thank you for any advice you can provide.

RG
Old 01-10-2019, 10:37 PM
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No warmup regulator, but there are Inlet Air Temperature and Engine Temperature sensors. It more than likely is some small vacuum leak somewhere, but you can check your fuel pressure with a gauge if you think that is the issue.

There are aluminum replacement pieces available for the cargo cover caps available somewhere out there in the etherworld. Look around.
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NASA/PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again
I can fix your late 944 Cruise Control module - PM for details
Old 01-11-2019, 06:51 AM
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kdjones,
Thank you for your reply. I will look into the temperature sensors.
My car has a fuel rail pressure gauge. I will check there, if I remember correctly, the pressure should be around 50 psig.

I will look for the aluminum parts for the cargo cover. Would you have any idea where?

Thank you!
RG
Old 01-11-2019, 09:51 AM
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Here you go:

https://944online.com/index.php/catalogsearch/result/?q=cover+caps
Old 01-11-2019, 11:43 AM
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The engine temperature sensor tells the DME to en-rich the mixture while the engine is cold. Thus making starting easier and cold idle smoother.
More than likely you have a bad sensor or wiring to it.
Sox
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Old 01-11-2019, 12:28 PM
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Sox
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Old 01-11-2019, 12:35 PM
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Thank you both for the information.
I checked at noon time here (32 degrees) the fuel pressure gauge read 40 psig.
Is this within range? I thought it should be 50 psig.

I will look into the cargo fittings and temp sensor next.
Thank you for your help!
RG
Old 01-11-2019, 01:58 PM
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2.5 bar if stock, which is 36psig.

Sounds like you are running a 3.5bar FPR, which is 50.7psig

You should only get this when the vacuum line is removed and plugged.
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NASA/PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again
I can fix your late 944 Cruise Control module - PM for details
Old 01-11-2019, 02:45 PM
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Does car do fast-idle of 1200-1300rpms when you start?
Old 01-11-2019, 09:47 PM
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In case you wanted a Vac/boost relationship to the fuel pressure....
Sox

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Old 01-13-2019, 10:07 AM
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Quote:
Originally Posted by Raulg View Post
kdjones,
Thank you for your reply. I will look into the temperature sensors.
My car has a fuel rail pressure gauge. I will check there, if I remember correctly, the pressure should be around 50 psig.
What pressure did you actually measure at fuel-rail at idle?
Old 01-14-2019, 01:12 PM
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I had stumbling and low power issues when my '86 951 was cold. The problem mostly went away when warm. After replacing a few things, it turned out to be the oxygen sensor. Car runs great right after startup now. I think the change interval for the oxygen sensor is 60k miles.


As for the cargo cover, I used 90 metal brackets from the hardware store. I put a few holes in them and screwed them into the back of the rear seat. They sometimes rotate loose, though.

For the fuel pressure, look at Clark's article: http://www.clarks-garage.com/pdf-manual/fuel-01.pdf
. I don't think 40 psig is too far off. Mine is 34 while running IIRC.
Old 01-17-2019, 07:20 PM
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Gentlemen,
Thank you for your replies. I appreciate the help.

The pressure at the fuel rail is 40 psig. I will check upon start up and report back.
My car idles at about 1000 rpm and then drops to about 750 within a short time.

It still runs rough when cold. I haven't changed the temp sensor yet. That is coming.
The car has other issues now. Some of you may see my new post about clunking noise.

Thank you for all the advice.
Your advice has help me keep my car running for a long time.
RG
Old 02-04-2019, 09:53 AM
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I am getting back to troubleshoot the car issues. Now that the weather is warmer, the stumbilng is not as severe. I do want to fix it.
Kdjones: you mentioned the "air inlet temperature sensor". Where is that located?

I changed the temperature sensor under the intake manifold near cylinder 1, long ago. It looks rusty. I will change that again. Is there a way to replace it without taking the inlet manifold out?

Garage DIY: Thank you for sharing your experience with the oxygen sensor. I changed it about 5 years ago. IT may be bad again. I am inclined to change it.

Thank you all
Raulg
Old 05-21-2019, 05:53 AM
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IAT is contained within the AFM (air flow meter).

I would get the DME Test Plan for your car and go through the measurements contained therein. You may find something is out of spec.

The temperature sensor for the DME (the blue one) is what may be out of spec, leading to rough running.
__________________
NASA/PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again
I can fix your late 944 Cruise Control module - PM for details
Old 05-21-2019, 10:01 AM
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kdjones,
is that the sensor under the intake manifold?
If so, is there way to replace it without taking the manifold out?
Thank you
RG
Old 05-21-2019, 10:49 AM
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Expect to take the intake off.
__________________
NASA/PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again
I can fix your late 944 Cruise Control module - PM for details
Old 05-21-2019, 05:26 PM
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O2 sensor won't make the engine stumble....
Why don't you test the engine temp sensor first rather then replace it.
Sox
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1986 951"MADDOG" black with maroon interior
All stock with shimmed WG
Old 05-22-2019, 12:54 PM
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Soxnail,
I figure that to test the sensor, it has to be removed. (intake manifold, etc).
It may be more practical to change it than test/reuse and risk a chance that it may fail soon after.
Any thoughts?
Thank you for your advice
RG
Old 05-23-2019, 07:58 AM
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Raulg,
You can test the sensor while it is installed. You are going to need a DVOM and a couple of cables with alligator clips on them. Car has to be cold (not been run and at ambient temp)
pic



Locate the sensor, you can see it looking down next to the hard pipe coming from the turbo.
Pics


Use a long needle nose to pull the spade connectors of the sensor.
Attach the alligator clips on each lug of the sensor.
Set the meter to resistance measurement.
and read the sensor resistance.
depending on your ambient temperature you will get a reading.
Table attached.



Now start the car and let it warm up, you should see the resistance on the meter display the temp to ohms relationship as shown in the table.
It won't be exact but any variation out side the range in the table means the sensor is, to use my technical term "Barfed"
Good luck, post results.
Sox
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"Little problems always come back and bring bigger friends with them".
1986 951"MADDOG" black with maroon interior
All stock with shimmed WG

Last edited by soxnail; 05-23-2019 at 06:44 PM.. Reason: Wrong pic attached.
Old 05-23-2019, 08:52 AM
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