RageLtMan

For the love of whatever god they believe in, can somebody help me??

I live in boston, and up until last week we've been enjoying a long summer here. However, for the last seven days we've been rainned upon incessantly. My 86 951 ran perfectly fine, the turbo was showing it's age, and on hard acceleration she burns oil by the bundle (using mobil 1 i suffer greatly for this).

Then all of a sudden as i came out of a local food and drink establishment (being the DD of course) i get into the car, which had been parked for an hour, and start driving. All is well, until two cyllinders cut out on me. Obviously, being the loving owner i am, i have her towed to the shop.

The first thing my mechanic finds is that the cranksensor on the bellhousing, closest to the rear of the engine, has damage to the wiring sheath, and he has me procure one from my parts car - an '87 924S. The crank sensor gets spliced into the harness and the car still refuses to run right. she idled fine, but revving her up even without loading the engine produced massive misfires and such.

We tested the ignition coil, and found that it was dying. So that was replaced, the wires all tested properly, at amazingly the same resistance independent of the length (prolly some porsche engineering trick to even out spark strength across the cyllinders).

The car is driveable, up to a point. On hard acceleration, like merging onto the highway, the engine bogs out. Interestingly enough, this happens in 3rd gear around 45 MPH on up. Which means spool range, as far as i know.

This bogging can't be good for my engine, it's sure as hell bad for merging onto a highway, and we're at a loss as to what is happening. My current theories are
A.) The turbo finally succumbed to the cold and is either putting too much oil into the engine, or not producing enough boost to match the fuel map in the computer.

B.) The crank sensor error did something to the computer (this is the worst case as i understand).

C.) gremlins.

I was wondering if anyone here had experienced problems like this. Ignition, other than the timing thereof controlled by the computer at load, has been tested to be working. Fuel pressure, is a problem since the nut at the end of the fuel rail siezed up. However, we tested fuel delivery volume to be the appropriate 850CCs in 30 seconds of cranking. That leaves intake, which is turbo oriented.

I'm going to run a gas test later today with him, testing under load, and i was wondering what values would indicate an oil-rich mix, or a fuel-rich one. Other than that, does anyone have any suggestions? Should i reset the computer? and how? Is there a way to test the computer to make sure it's ok? Anyway, thanks for any and all input, i'm sure you all understand my trepidation and fear for my baby's health .

KuHL 951

My 951 started to bog out at onset of boost or any heavier throttle but drive fine under these thresholds. My fuel filter was plugged, FPR was way out of spec, and I had a witches brew of small vac leaks. The fuel filter and FPR changeout was all it took for mine. I went ahead and did the venturi delete to get rid of the other nuisance leaks and it runs outstanding now. I've found that when a fuel filter gets clogged, it gets clogged real fast, usually after letting your tank get down to reserve. I assume you checked the rotor, they can lose a piece of plastic and wobble, especially at higher rpm.

RageLtMan

FPR? sorry, i'm a lil dense on the lingo

KuHL 951

Fuel Pressure Regulator

testarossa_td

Here are a couple to get familiar with.

TPS(Throttle Position Sensor)

AFM( Air Flow Meter)

RageLtMan

is that the one at the front or back of the rail, i'm a bit rusty since i haven't done fuel delivery work since i drove the S.

thank you testy , the alzheimers hasn't set in that badly at the ripe old age of 21.

KuHL 951

It's the one in the back. Like was said above, open and close the throttle by hand and make sure your TPS clicks both up and down. Whatever happened has come on quickly so it more than likely is a failed component, I wouldn't suspect your turbo yet. Check for vac leaks, these cars are plagued with them.

testarossa_td

Of course remember on the turbo TPS it can fail anywhere along it's travel, the click is the quick answer. I think Clarks garage has a writeup on the voltmeter fun...

Alpine951

I had some similar symptoms. My car is 19 years old!! Since buying it 5 years ago I have removed the injector rail and injectors about four times. There are some threads on here that talk about a problem with the insulation on the fuel injector harness's (pigtails). This is the wiring right at the plastic connector that attaches to the fuel injector. Because of the heat under the hood and the age of the wring the wire insulation on the injector pigtails gets hard and brittle. It tends to crack and fall away. removing the injectors helps this along as well since the insulation is brittle. You won't know unless you split open the rubber boot at the end of the pigtail. There are some tests that may tell if there is a short caused by the broken insulation. I copied this from an email I receved from a trsuted source. If its this you can buy new pigtails at NAPA that you splice in.

Here's the test for the injector connectors, lets
you track which one, or more is bad. The 1st set
of tests checks for proper operation of the +12v
power line to the injectors and the 2nd
continuity tests check for the condition of the
ground (activation) wires on the injector harness.

1. disconnect DME
2. disconnect idle-stabilizer, CV-cycling valve
3. disconnect all injector connectors, be careful
to remove the spring-clip first, then pull on the
connector itself, don't pull on loop of wire.

POWER-LINE TEST

4. using battery-ground as ground, use a
voltmeter to check for +12v on each pin of
injector connector
5. all rearward pins should have +12v
6. all forward pins should have ZERO volts
7. if you have ANY voltage on the forward pin,
then you've got a short in that connector.

GROUND LINE TEST

8. Also check ground pairs (forward pin)
9. set voltmeter to ohms and check continuity
between forward pins of injector #1 & #2: should
read zero ohms (connected)
10. check between forward pins of injector #3 &
#4: should read zero ohms (connected)
11. check between forward pins of injector #1 &
#3: should read infinite ohm s (not connected)
12 check between forward pins of injector #2 &
#4:should read infinite ohms (not connected)

Eyal 951

I'd check the TPS, since you already replaced the coil. if that doesnt change anything, look at the fuel system. I would do vacuum lines whether they are related or not, EVERYONE with a 951 should do them now.
Does the car have any mods?

Rip It

check all the simple/least expensive things first...vaccuum leaks

RageLtMan

ok, so i'm off to see the wizard and try to figure this out. seems the consensus lies on fuel delivery or TPS. though the TPS has been a bitch before, i thought that problem settled. it's unlikely to be the culprit though due to perfect functionality without load. nonetheless, better safe than bogging. I'll check the FPR, and replace the filter - it's been about 50k since i did anyway. thanks, i'll let you guys know how it went.