Porsche 930 (1987)

[stownsen914]

The fact that the car runs well for 5 mins and then runs poorly is a clue that something goes bad as it warms up. I saw a suggestion above to check the ignition coil. A compromised coil can have symptoms you describe. Coils are easy to swap out and see if the issue goes away.

[Horneck]

I will change the sparks tomorrow and take the intercooler off a s well to check again for boat leaks. What is the best way to check for boost leaks on top of a visual check?
What are you guys thinking about the 6% C/O at idle. Maybe this goes ultra rich under boost and initiates the misfire?

[Alan L]

if you have a boost leak it will go rich, irrespective of idle mix.
Pulling it apart to find a boost leak will only help if something is broken there - eg O ring.
The best way to test is either a smoke test or pressure test.
Regards
Alan

[Horneck]

I have reviewed and replaced today all o-rings from the turbo to the intercooler and have checked all pipes fir leaks with no real finding and improvements. Have changes all sparks as well and they were full of black carbon as well checked that both fuel pumps work.
Car still misfires above 2500. Have measured CO and it showed at idle 8%.
Will measure system and fuel pressure as I think it is a fuel driven issue. Where can I get the required system and fuel pressure for the turbo from? Cannot find it in my manual.
If anybody has more good ideas what to do next please let me know.

[Alan L]

System pressure around 6.5 bar, warm pressure (WUR) 3.6
Your idle CO will be inconsequential.
The best way to check for boost leaks is to smoke or pressure test. Something may be lifting under boost. But you are on the right pathway.
Alan

[flightlead404]

Originally Posted by Horneck

I will change the sparks tomorrow and take the intercooler off a s well to check again for boat leaks. What is the best way to check for boost leaks on top of a visual check?
What are you guys thinking about the 6% C/O at idle. Maybe this goes ultra rich under boost and initiates the misfire?

6% co is a 12.25:1 AFR (assuming pump gas) roughly. That's probably a bit rich for a warm engine, but a bit lean for a fully cold engine. Where are you testing it and is the engine warm (oil temp 90c or higher)?

Spec book says the US adjusting value for %co is 0.6% - 0.2% which is in the low-mid 14's AFR. For me, that would be too lean.

The type 930/66 (Eu and Canada) specs are 1.5% to 2.5%.

All that said, idle mix is just that, idle mix. Once you're off idle, above about 1,500 rpm the mixture is set by the control pressure and that is set primarily by the WUR. If your idle is fine, and your control pressures cold, warm, and on boost are in spec, I seriously doubt that is the issue.

[Horneck]

I have checked twice for air leaks and will do a smoker test next. Have changed all o-rings between turbo and intake with no effect. Just got my fuel pressure gauge will report the readings in the next few days. I think my problem is the fuel or system pressure.

[Horneck]

I have measured fuel pressure of my car today and appreciate feedback from the group to what problems the readings point to.
Year of engine 1987. US model, WUR (hard to read) 0 438140 153. Found 742 stamped on the housing as well as a 40 printed on the side.
Temperature at test 80F, WUR resistance 0.26k Ohms
System pressure with both pumps running :6.5 bars
Cold control pressure: 2.9 bars
Warm control pressure at the same 2.9 bars if I measure the car without the pumps running
Residual pressure without the pumps running after 5 min 2.5 bars, after 15 min 2.0 Bars

If I read the data correct my WUR is not dropping the control pressure when the engine warm. Correct?

Who can rebuild my WUR? or where can I buy a new one?

I found another issue. At idle with the car running (1000 rpm), my pressure gauge jumps between 3-4 bars. When I rev the engine to 2000 it stabilizes at a 3.5 bars and is fully stabile at 3000 rpm at 3.9 bars. What does this indicates?

Thanks for your advice

[Alan L]

You have some weird stuff going on - may be the cause of your problem.
Your cold pressure is quite high - but then we need to know the temp that was taken at - it is a sliding scale.
The pressure should rise to around 3.6 after 5 min. The fact it seems rpm dependant is weird also. Almost suggesting a voltage problem - for the pumps and WUR.
Residual pressure is good - no worries there. The pressure should not be jumping at idle.
I suggest you check the voltage supply at the WUR, and somewhere in the fuel pump supply side (front fuse box) while engine running.
Alan

[908/930]

The pressures I have used,

CP cold 1.0@10c 2.2@40c
CP warm 3.65+-0.2
System pressure 6.0 - 6.7bar

[Horneck]

The cold pressure of 2.9 b was measured at 80F or 22C. What I don't understand is how I can have such a rich idle 8-9% CO.

[Horneck]

Sorry mistyped. 80F is 26C

[Alan L]

Your CP is too high (out of spec -2.5)
But you have other weird things going on. I would verify voltages first - before pointing the finger at the WUR. Altho the CP is a mechanical setting and is erroneous. The rest of the behaviour needs an explanation.
Lets see if you have stable (12-14) voltage at idle.
I wouldn't worry about idle CO until the weird stuff is sorted.
Alan

[Alan L]

Also measure V across the pins in the WUR plug - Key ON.
Alan

[flightlead404]

Interestingly I just checked the factory manual and noticed for the first time in looking at this a million times, that the graph doesn't match the textual specs.

the WUR part number for your car is 930.606.105.ex I believe, but double check that.

Bosch pn 0.438.140.153

Cold control pressure on the graph is 1.9 bar +/- 0.2 bar
Warm control pressure on the graph is 3.1 bar +/- 0.2 bar
With boost enrichment (0.8bar pressure on the nipple) 2.6 bar +/- 0.2 bar

BUT

in the text it says warm control pressure 3.75 bar +/- 0.2 bar
with boost enrichment 2.9 bar +/- 0.2 bar


Anybody else seeing this?

[flightlead404]

Originally Posted by Horneck

Warm control pressure at the same 2.9 bars if I measure the car without the pumps running

Not sure what this means, the testing methodology has the pumps running when you make this test.

There is a further warm test where you apply 0.8bar of pressure to the brass nipple on the side to check boost enrichment.

[Horneck]

Just a brief update about the progress finding the problem of the car.
Just have purchased a remanufactured Warm Up Regulator and the pressure fluctuations of my fuel system at idle is gone. The system and control pressure of the system is now within the expected levels.
Unfortunately the problem with my car actually has gotten worse.
After a brief 1 mile warm up (car behaves as expected with no problem to rev up) the car now starts to misfire starting at 1800 rpm. When the car is warmed up the CO at idle is 9% and the car is blowing black (maybe blue) smoke. For sure it runs way too rich. Start up and idle is perfect. As soon as the car gets into boost the problem occurs.
I am at a loss running out of ideas what to check next. Cannot find any boost leak and I am starting to think that maybe my turbo is blowing oil into the cylinders?
Please let me know what you would check next as the car is not drive-able.

[Alan L]

Some confusing info. Hard to make sense.
Problem starts when get in to boost. But then is misfiring at 1800 rpm. Are you in boost at 1800 rpm?
Start up and idle is perfect. But then you say the car is blowing black (maybe blue) smoke at idle.
Alan

[Toddrivers]

I guess more information is needed. Do you have an Air Fuel ratio gauge hooked up showing what is going on cold, warm, idle, steady 3000 rpm, 4000 rpm, in boost?
What is the # on the Wur that you purchased, is it modified to be adjustable?
Do you have fuel control pressure numbers (cold and warm) that you can post?
Do you have good 12v power to your WUR?
Engine oil level can sometimes be too high causing the engine to burn oil which could explain the blue smoke. Mine is about right when just below the full line hot, maybe a qt low cold.
Good luck!

[Horneck]

A little more clarification to the situation of my car.
My initial problem started when I could not rev the engine over 3000 under load. When I was driving the car carefully with 20% throttle I could accelerate the car up to 4-5000rpm. Idle and start up perfect but high CO (9%). I have no AF sensor installed in my car and can only measure at idle.
My system control system pressure was 2.5 and did not change during warm up. In addition my fuel system pressure jumped at idle between3-4 bars.
To address the situation I have bought and installed a reconditioned WUR and my idle fuel pressure fluctuation is gone as well as my control pressure issues have improved.
System pressure is over 6 bars and control pressure (cold engine in FL at 80F) is 2.5B raising to 3.2 maybe more when the car warms up.
I thought my issues were fixed and I took the car out for a spin and initially the car accelerated well with no issues. After approx 1 mile or 5 min driving my problem reoccurred but now the engine misfires starting at 1800rpm refusing to rev any higher under load.
When I let the car run in my garage at idle the car starts up fine and idles great but when I try to rev it higher (without load I can rev to 6000rpm) I see black smoke coming out of my exhaust and my new spark plugs are black. Not sure if this is too much CO or burned oil.








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