jb944t

Hello all,
I Recently (had for maybe three weeks) purchased an '88 951, and have had nothing but troubles so far (love the car though).

First, a terrible "bucking" issue that occurred from 2500 rpm's on - which seamlessly worked into a turbo debacle (fins missing on compressor side).
I had the turbo rebuilt and re-installed it believing that the "bucking" would be gone (nope . . . bucking was still there).

Next, per the request of the turbo re-builder, I went through the vacuum lines and disconnected the manual boost controller. During that process, I found that the vacuum delay valve (timing valve) had one broken port (the one that goes to the waste-gate), so I installed a new timing valve and went for a test drive. I noticed the "bucking" was back and slowed to a stop. In an act of desperation / anger / embarrassment, I floored it through first (ran pretty good) and about 1/4 of the way through second it just . . . strangely shut down. I remember seeing the boost gauge react to my pressing the accelerator. Lights were functioning, as well as steering. . . but the engine would not rev.

After pulling over, the car would not start. It turned over normally, but would sputter a little then die. Had a spare DME relay, tried it, but that had no effect.

Towed it home - very sad

Since then (a week ago tonight), the car "starts", if stumbling around at 400 rpm's constitutes a start. If I give it ANY gas it dies. It sounds like an old British WWII airplane running out of gas as it "idles". The P.O. installed a fuel pressure gauge on the rail, which indicates ~38.

Today, I swapped the rpm sensor, but it made no difference.

My suspicion is that the timing belt skipped and that the motor is "done" (for the moment). Would it run (again, I use that term loosely) if the timing belt went kaput???

If anybody has heard of this, please respond.

Thanks so much,
JB

jerome951

Go through all of the vacuum lines and connections on the intake side. Sounds like you could have a massive air leak.

Where are you located? If near me I'd be happy to lend a hand troubleshooting.

Ronin-951

'Clarksgarage.com'

divil

You can check the timing easily enough: turn the engine over with a 24mm deep socket while you watch through the inspection hole in the cam sprocket housing. You'll see when the cam is lined up correctly. Then look down through the flywheel inspection hole on the top of the bell housing. You should see the mark on the flywheel lined up. To really see it lined up properly, you'll need to get right up there so you're looking straight down. Clark's Garage has pics that show how it looks from the normal angle.

If you have both marks lined up at the same time, your timing didn't skip.

Wald944

Check these 2 threads...near identical issue.
I myself am still troublshooting.

https://rennlist.com/forums/944-turb...help-asap.html
https://rennlist.com/forums/944-turb...sles-fine.html
https://rennlist.com/forums/924-931-...lem-fixed.html

numbskull

Check the spark plugs, wires, fuel pressure, cap/rotor verify spark. I had that exact condition with clogged fuel filter.. really clogged from sitting. Also make sure maf electrical connector to throttle is seated well, clean the connectors. Just a start, see clarks guide for sure.

jb944t

Thanks jerome951, but I'm in SW Florida.

I just finished checking the timing. I feel pretty sure that the 'ol girl is still in time! On my clutch housing, the reference indicator is longer than the line across the flywheel, so, all I can say for sure is that the line before "OL" is directly under the indicator - and - the cam gear line is angled to a small raised "dot" in the upper right-hand corner of the housing.

As for further testing:
Spark plugs are looking like coal miners . . . and gaps are not uniform-
Since it does technically run (starts and idles terribly) I must assume there is spark.
I have fuel pressure at the rail.

numbskull, did yours idle (terribly) and die if you gave it ANY fuel?

Wald944, Will read the threads completely asap!!! Thank you!

Heading to the store for celebratory beer... Going to re-check vacuum lines.

Thanks so much!!!
JB

Josh B

Post up some pics of the car and engine bay and let us know what modifications have been done to the car. I had the same problem and it was that an aftermarket MAF installed on my car wasn't getting power.

jb944t

10-4

numbskull

Yeah, when the maf connector was loose it ran badly and died when giving gas. If fp is stable what is vacuum hg at idle, is there a boost gauge installed or do you have a tester?

jb944t

There was a boost gauge in the vehicle when I purchased it . . . but . . . it was such cheap junk that I removed it from the equation.

jb944t

Josh B,
Could not upload . . . "upload file failed". Will try different tactics later.

Engine modifications that I know of:

Evolution intake pressure relieve valve
Tial wastegate (size?) (it's aluminum in construction and color)
Blue "silicone style" vacuum lines
"944S Super Six" turbo

Thank you,
JB

jb944t

jb944t

Car also has manual boost controller which I took out of the equation.
Ok, so not the timing... What else might cause a shutdown in mid boost?

I tried switching out the dme with the original that came with the car (was told is was broken).. would not even produce the bad idle.... was
not sure what to make of that test. Also tried jumping out the klr no difference.

YZ250

Sounds similar to something I had once, although yours is worse. Try disconnecting the throttle position sensor connector. If the car does better, then a new TPS is in order. This fixed a similar bucking/throttle sensitivity issue for me.