1987 924S "Bucks" then stalls

[Dave Tracey]

Hi All:
Well, after working through many electrical/ fuel / oil leak issues it seems that my 1987 American spec 924s has developed a peculiar problem. I have searched and read through a number of old threads on this problem, but it seems as if I have done everything that the threads suggest. This is gonna be a long one, here goes......

-I'm on the highway this morning, just after 6:00am. Been driving for about 20 minutes, 5th gear, steady at 60mph.

-The car starts to lurch and buck violently. I spill coffee on my new KISS concert shirt and in my lap. It was hot. I am now pissed. By "lurch and buck violently" I mean something like this; imagine you are driving around in 4th gear, doing about 25 miles per hour. Quickly take your foot off the gas pedal, then just as quickly blip the throttle, then quickly remove your foot from the gas pedal, then blip the throttle quickly again................ repeat several times. You get the picture.

-I give it more throttle, the engine bogs right down, the rpm needle buries itself and the engine stalls. The battery light is on. I restart the engine with the key and the clutch pedal pushed down. Restarts no problem.

-I get the car in 5th gear, giving a good amount of gas. It starts to happen again, almost immediately.

- I push in the clutch pedal, the rpm needle spins right down to zero and the engine stalls.

-I coast to the side of the highway. Ignition is still on, still in gear. I let the clutch out, the car starts back up again.

- I drive a few hundred yards to the next exit from the highway. Turning off to the right it happens again. Again I let the clutch out and the engine restarts.

- I limp into work driving slower (~45-50 mph). No further problems.

-Car sits for 10 hours. I drive home (off the highway, ~50mph). No problems.

What the heck??

I've had the ICV removed and serviced/ cleaned recently which cleaned up my idle hunt quite a bit. The DME relay has, allegedly, been replaced recently. (I have a spare new one and will try that). New fuel pump, fuel filter, plugs, wires, distributor cap, rotor, CTS, some vacuum hoses (I've done a lot of the 'ol propane checks recently), quite a few new fuses,wiper relay.......the list goes on. My mechanic said that my grounds looked ok.

Like I said I've gone through the old posts, with the exemption of the DME relay I think I've covered everything off. I'm wondering if there is any new wisdom out there that can be shared- links would be VERY much appreciated!. I was thinking of making my own temporary engine to battery ground to see if that makes a difference at all as well.

[Grandad#3]

Hi Dave, Just athought, but have you checked the connections on the Speed / Reference Sensors? They get brittle and break apart, result = Bad Connection. They are at the rear center of the engine in a bracket just forward of the firewall.

Cheers,
Larry

[Dave Tracey]

Hhhhmmmm........where might this sensor be? Is it on top, kinda under the last intake plenum branch, closest to the firewall? I just noticed something sitting there all by itself on top of the engine, with a broken bracket.

If this is it I'm wondering if my mechanic, when removing the intake to get at my ICV, broke it off by mistake.

[Grandad#3]

Hi Dave, I tried to find a picture of the bracket I'm talking about but can't. The bracket is at the top rear center of the back side of the intake manifold, but not attached to it. It should have two square openings for the Speed / Reference Sensors connectors that plug together. You pull the plugs apart when you change the sensors. One side goes to the DME and the other side to the sensors themselves, which are mounted on the top driver side of the bellhousing. Check out the link below for clarks garage.com. you will see A -Z, click on S and it will take you to the Sensors and how to check/replace them. They are a real PITA to change out. I don't know if Pelican sells just the connectors, but 944 online.com does sell them. You can do a "SEARCH" at top of page for "Reference Sensor" or "Hard to START". Read thru clarks garage as it has a wealth of great info to help you work on your car.

Clark's Garage Shop Manual Index

Cheers,
Larry

[running_cold924]

my S did the same thing, found it was a bad tank of gas from a place i'd never bought from before. ran some HEET through it to about a half a tank and filled with some gas from a reputable place. end of story.

[Rasta Monsta]

I like the gas theory (run Chevron ONLY) and the ref sensor theory.

I would also reach into your glovebox, pull out your spare DME (which as a wise 2.5er, you have in there) and swap it in. I might also check the connection to the computer. . .make sure pins are bright and shiny and none are bent.

[wild man]

Sounds like possible air/vacuum leak. Check vacuum & intake hoses (make sure they are are on all the way, and the clamps are tight.