samana76

Hello everyone.

I have a wonderful 1986 951S which was running like a gem up to just to about two days ago. I took it for a 200 mile trip and all of a sudden it started running rough. All the fluids were there, no low oil or anything. It idles really rough, it hesitates when I take off from a standing still, is rough on the freeway although the engine is very strong.

When I got home I noticed the exhaust manifold was very slightly loose and there was a minimal leak do to this. I tightened it and the leak went away however that did not correct the problem. After I tightened it I also drove to my exhaust specialist and he said he did not here any exhaust leak. He suggested I check the plugs as the roughness sounded that it might have to do with that.

So I got back home and checked the spark plugs. All of them except for one were excellent, one was a bit black (cylinder 2 counting from the front of the car). I noticed I do have to replace the ignition wires as two of the wires ripped from the plug socket (the rubber between the wire and the plug socket end) as I was removing them (I taped them with electrical wire momentarily).

I'm thinking it might be a fuel delivery issue. I did reach the low end of the reserve tank twice last week and I am thinking some debris might have clogged the fuel filter or injectors. However I do not have the time to start looking into the issue and really need the car working well and soon.

So my question is: can anyone suggest a very good garage which deals with 944s in the Bay Area, preferably in the Burlingame - San Mateo area. I have Holland Service just two minutes away from me and the previous owner brought the car there a few times to get checked. They seem to have a great reputation however I do not know how specialized they are in 944 turbos. Does anyone here have any experience with them or can suggest a another reputable garage?

I will try to post a video of the issue should anyone have suggestions on what it could be as I a would like t know even if I might not be able to get my hands dirty this time around.

Thank you all on advance.
Igor

samana76

For anyone interested here is an update on the situation.

I brought the car to the mechanic where the previous owner used to bring it - D & J Auto Repair in San Bruno. They seem to be a reliable and competent garage and they had actually rebuilt the head of this car in 2011.

I just called them and unfortunately the head mechanic said that it might be a problem with a valve in cylinder number 4. He will do a leak down test today and will let me know what exactly is the problem this afternoon. If it is a problem with the valve he says that I am looking at a ~$2000 repair bill. What seems a little strange to me is that if the head was rebuilt about 2 years ago how can their be a problem with the valves? The engine has always been very well taken care of.

In any case I am posting a video where you can clearly see how rough the engine is running.


If I really do need the valves to be replaced, does anyone have any suggestion on what valves I should replace them with. Are there more performance oriented valves I can install? While the head is out is there anything else I should consider doing?

Finally, if I need this work to be done, can anyone suggest a top rated Porsche garage in the Bay Area (preferably San Mateo - Burlingame area) to have it done?

Thank you all for your help.
Igor

adrial

A valve letting go in 2 years (max 20k miles?) is not typical.

Is the engine running stock boost?

If the engine is running strong then it sounds more like an electrical (TPS, AFM, etc) issue.

samana76

Hi Adrial,

Thanks for the quick reply. I just recently, about 3 months ago, installed a few upgrades to increase the boost slightly. The upgrades are the following:

- installed 3.0" Fabspeed performance exhaust package
- installed Tial 38 dual port wastegate
- installed Rogue's A-Tune Package
- installed a Lindsey Racing manual boost controller
- installed an Autometer Sport Comp Boost gauge model 3301
- install a Innovate Motorsports Air Fuel Ratio gauge with wideband controller and oxygen sensor
- replaced spark plugs with NGK BPR7ES

I am always running the boost at ~18psi which is the maximum Rogue's A-Tune Package will allow before entering over boost protection mode.

When pushing the engine in the freeway I notice no difference in pull compared to when the engine was running smoothly just the a week ago.

If it is an electrical issue, how can I check this?

Thanks.
Igor

samana76

I forgot to mention that the mechanic did a compression test and found that cylinder #4 had very low compression of 60psi while the other three cylinders and even compression (he did not say how much).

I would appreciate any thoughts and recommendations on garages in the bay area and parts I should consider buying to upgrade the ones I need to replace or anything else I should do while I have the cylinder head off.

Thank you all again.
Igor

Tom M'Guinn

Hmmmm....


Try pulling the injector clips off one at a time and see if any one cylinder is not firing. Pull the clip on injector 1 and confirm motor runs much rougher. Reinstall that clip and pull the second one... Etc.

Crazy Eddie

How typically accurate, are compression tests ?

333pg333

At first I thought it sounded like a pretty decent exhaust leak but then from other angles of the video it sounds like a cylinder is missing. i.e. inj or spark.

adrial

If you are getting fuel, but no spark, you could wash down the cylinder walls and cause low compression.

Check spark on cylinder #4. Replace the spark plug wires for sure.

86 951 Driver

Its missing a cylinder for sure. I would do what is recommended here. Check for spark. Possibly get a spark tester from Autozone and connect one side to the plug and the other to the wire on cylinder 4. See if it has spark.

samana76

Thank you everyone for your help. The mechanic I brought it to will perform a leak down test and will let me know the results. I hope it's not a valve issue.

I forgot to mention here that when I was inspecting the engine before bringing it to the mechanic I could definitely smell fuel near cylinder #4. That is why I thought it could be an injector problem. In any case, once the mechanic completes his inspection, I will see what needs to be done and ask you all for advice again.

I truly appreciate everyone's help. I have always received great and friendly advice on this board.

Thank you.
Igor

carlege

i wouldnt let the mechanic do the valve test or leak down until i have ruled out spark and injector pulse being present.

kev951

If I was still in the bay I would have said come over

carlege

If 1 cylinder wasnt working you should notice a significant difference in the AFR on your gauge?

samana76

Hello everyone,

Sorry for not answering sooner. I appreciate everyones contribution to this thread. Unfortunately I had already brought the car to the mechanic and could not do the checks suggested. In any case I spoke with the head mechanic yesterday and he told me he performed the leak-down test which pointed towards a valve leak, he then removed the head and confirmed the exhaust valve on cylinder 4 is burned. He also told me that in 2011 they did not perform a head rebuild but just replaced the head gasket. At the time the valves were OK and did not need attention.

He also said that most likely the valve burned because after performing the upgrades listed above the engine was running too lean for the added power at high RPMs and that this increases the temperature in the cylinders which results in burning the valves. He says that everything else is fine.

So I need to replace 4 exhaust valves. This is a 1988 944 Turbo S and I know that Porsche used special exhaust valves, larger sodium cooled exhaust valves, for this model compared to the normal 944 Turbo. I would like to replace the exhaust valves with this model's original valves or, as I do take this on the track every once in a while, with upgraded performance exhaust valves (and maybe valve springs at that point), if they exist (I could not find any information on performance exhaust valves, only springs). Can anyone please suggest which exhaust valves I should install and where I can get them. I know original Porsche valves (however I'm not sure they are the S model version) are around $150 each as opposed to half or less for aftermarket ones, however I prefer to have the original or upgraded ones, even if it costs more.

Also, since the cylinder head has been removed, are there any other, not highly expensive, upgrades I can do?

Finally the mechanic suggested, after he has finished the engine work, that I bring the car to a tuner to have the chip mapped appropriately for the state it is in. I have a Rogue's A-Tune Package installed and I thought this was mapped correctly for the increase in boost. Do I have to get this chip remapped by a tuner? If so can someone suggest a tuner in the Bay Area?

Thank you all once again for you comments and help. Please let me know about the exhaust valves and any additional upgrades you think I should do as soon as you can. I would like to advice the mechanic later today as to what I'm planning on doing.

Thank you all so much.
Igor