sghost

Hi all,

First, apologies for not using search -- I'm on my phone and it's very difficult. I recently got an oil change and tune up and smog test for my 89 964 C4. Everything came back with flying colors and the car ran great for a week. Today, any time I apply throttle under load, the car jerks and stutters and just drops to idle rpm. For example, going from a stop or uphill - I put it in first, let out the clutch but the car just drops to 500 rpm. I have to overrev to get it going.

my mechanic took it for a spin and scratched his head saying he needs some time to look into it. Perhaps someone here has had a similar problem that can offer some things I could check for?

Makmov

broken dizzy belt

sghost

What does it look like / how accessible is it?

BGLeduc

Give this a look:

https://rennlist.com/forums/964-foru...r-dummies.html

If this update has not been done, it is worth a shot. If the issue is intermittent, this may be your fix. I had my car for a few months after I bought it in 2001, and all was well. Then I had major service, and started getting symptoms like what you describe shortly after. This was the fix for my car.

Good Luck!

Brian

Makmov

Its the belt that runs the secondary ignition distributor head.

Pull the caps off and the dust covers. Looks like a small cog belt.

Could be that wiring harness deal, as well.

dfinnegan

Here's a pic of the distributor belt (in a disassembled distributor pair)

sghost

Thanks, guys. I had to move the car tonight for street cleaning and it got much, much worse. I can barely idle for a minute before the car completely stalls. If it kicks over 3,000 rpm, though, it runs just fine.

sghost

Pardon my ignorance, but is it the twin canister looking thing at the bottom left corner of the engine bay, with lots of tubes coming out the top? My mechanic pulled out a tube from the side while the engine was running and pointed out to a belt that was moving in there, so perhaps that's not it.

Could it be "limp-home mode" that I'm reading about in the guidebook?

tbennett017

Yes that is the twin distributor you're describing... those tubes are high-tension wires that feed the spark plugs. There are two duplicate plug systems on your car. Two plugs per cylinder.

Another test is to run the car with the center plug disconnected on first one then the other distributor cap. I strongly suggest you DON'T run the car unnecessarily until you can rule out the distributor belt failure. It can fail in a 'good' spot or a very very bad spot... causing damage to your car. Also check into the link above regarding the wiring harness.

With the car off, you can also remove both distributor caps, and gently try to rotate both of the distributor rotors. If the lower one rotates freely, then your belt has failed. At that point you could conceivably remove the secondary rotor (the one that spins) and button the rest back up to get it to a mechanic.

If you feel like this is over your head, tow it to the mechanic. Don't run the car with a broken distributor belt. It might be fine, or it might go very badly. Too risky.

Indycam

Do you have a spare dme relay ?

kenloen

have you checked the MAF hasnt come loose/popped off at the manifold connection?

Jacke2c

You might want to check the large rubber gasket/o-rings that connect the two banks of intake manifold together. I have seen this cause exactly the same symptoms. The backfire will push them apart and then allow air to leak into the intake system causing erratic idling, stalling, and sever hesitation only overcome y excessive high RPM's to make it run smoothly. About a30 minute fix to loosen all the clamps, realign the manifolds and re-tighten the clamps.

sghost

Thanks for all the suggestions. I'm not the most capable when it comes to engines, but I did glance over all the tubes and belts. I didn't want to take apart the distributor for fear I may not be able to put it back together.

Here's a video - I disconnected the primary distributor hose and it revealed a moving part inside, so I assume the belt is fine? The car idles a litte rough and when I apply throttle, it revs for about a second, then nearly cuts out. Sometimes, there will be a loud "pop" from the airbox. Does this reveal any other clues?

http://youtu.be/m9jzFu2qlBk

Makmov

well that is the primary, and it is gear driven.

sghost

I'm happy to paypal someone $100 if they can accurately prescribe a fix I can perform without a visit to the mechanic, or if you're in the bay area, can fix it with me