RJB

Well, I am at the end of my ability to diagnose this problem, so I am really hoping that you can help me out. Let me describe the symptoms of the patient. First, this is a 1987 944 NA that has about 190,000 miles on it. I know that the previous owners replaced the head gasket and some of the valves a couple of years ago. What I am seeing is a puff of smoke and hesitation in 2nd and 3rd gear when the car starts up. It goes away when the engine warms up after about 3 to 4 minutes. The smoke is white and it smells like gas.

Here is what I have replaced and cleaned. Starting with the fuel system. I have replaced the DME relay, fuel pressure regulator, fuel filter, and had the fuel injectors cleaned by professionals. I have replaced the AFM, the DME engine temperature sensor, tested and re-adjusted the TPS, and the spark plugs.

I did a compression test today and the results are

#1 150 psi
#2 165 psi
#3 170 psi
#4 175 psi

When I looked at the spark plugs today, they all looked clear - not too clean. I do not think radiator fluid is leaking into them, as they were not wet. The smoke is definitely white and I have seen in previous threads that this is from radiator fluid - however this does not smell sweet - it smells like fuel. I am getting about 23 MPG, the oil is clear, the radiator fluid is clear, and I am not loosing either fluid.

The only thing I can think of is that I am getting some type of fluid past the rings in #1. The car runs great when it is warm. The hesitation is a nuisance.

I would appreciate any help or advice as to what to check next.

Thanks!

t1tec

You might have a fuel problem.

To much fuel being dumped in the cylinder, the engine is struggling to burn the extra fuel at low rpm.

I would check the injectors, you should be able to check and see if they are pulsing correctly.

Sami951

How cold is it out there? Over here it's been around 25-40F lately and every single car puts out some white smoke until they warm up.... it's apparently just condensed water in the exhaust pipe, nothing to get worried about.

It seems like my 951 runs slightly lean when the engine is cold, dunno if my engine temp sensor is busted or something, but in any case it causes some definate hesitation - and cures itself in just few minutes, as soon as it warms up some....

Not really helpful, I know

RJB

t1tec,
Thanks for the suggestion, but I just had the fuel injectors rebuild. Are you talking about the electrical signal to open the injectors being on for too long? If that is the case, how would I test for this.

Sami951,
I live in Texas, so it does not get too cold here - certainly not close to Finland! The smoke and hesitation happen when the outside temp is warm (80F or higher) and when it is cold (in Texas 45F or below), so I don't think it is related to the air temperature. It just goes away when the engine warms up to its normal operating temp. I don't believe it is condenced water because of the smell.



Thanks for the suggestions. Does anyone else have any thoughts.

Peckster

You didn't say how you checked the plugs. To test for coolant, let the car suit overnight, start it for 10 seconds or so, then check the plugs. Coolant tends to leak into the cylinders after the engine is shut off.

Red 944

o2 sensor?

skipgresham944

If all else checks out OK (fuel system components especially, also whether getting good spark to all cylinders), you need to consider whether you have a defect in the cylinder head assembly (most likely a bad valve spring) that is preventing complete combustion when cold.

This will cause fuel to be vented with the exhaust, creating the light smoke and fuel smell you are getting. This type of problem can ruin your catalytic converter (who cares) but more importantly can cause cylinder wear from gasoline washing of lubricant from the walls, if there's enough non-burned fuel.

Saw this situation on a couple of 944 cars before. Very tough to diagnose, essentially gets found when all else is ruled out and the engine gets torn apart to inspect. Hope it's not the case, but not that big of a deal if caught early.

RJB

Peckster,
I did not check the spark plugs by letting them sit overnight. I checked them when I did the compression test and the engine was at normal operating temperatures. I will check for coolant when I get the car back in the next couple of days. Thanks for the suggestion.

Red944,
I forgot to mention that I had replaced the O2 sensor as well.

Skipgreshem944,
I hope this is not the case either, as I have no way to diagnose this and really don't want to tear the engine apart. While the compression in #1 is lower than I would like it, I did not think was low enough to pull the engine and tear it apart.


One other item I forgot to mention is that I am using the Bosh Platinum +4 spark plugs. I have searched the archives and found numerous oppinions on various spark plugs. Again, it seems to run fine when the engine is warm and none of the electrodes were fouled. They just had the normal gray deposits on them.

If anyone else has any suggestions, I would appreciate it. If not, then I will just have to live with it - arg!