ebs

My friend's 1989 944Turbo (26/8 turbocharger version) had an issue today when feeding in the power. It happened around 60 mph in 5th gear. As he started to accelerate hard in top gear, the car hesitatated and would not rev (like there was no fuel), causing it to stumble. He fed the power in gently and it seemed okay. Later the same day, the same thing happened again. It has never done this before. The car is 100% stock.

What do you think it could be?

Many thanks in advance.
Ebs

special tool

Overboost protection.

First item to check is the pressure signal lines. Particularly the line from CV to wastegate. You are looking for a split/hole.

ebs

Thank you. We will look into that. I was thinking a problem with TPS or DME relay. You don't think this is likely to be the cause? Being mechanically challenged, I find diagnosis difficult.

If its not pressure signal lines, any other suggestions to check?

Thanks again.

Tom M'Guinn

How's the ignition? High load stumbles on turbo cars very often point to bad plug wires -- or cap, rotor, plugs themselves.

reno808

Ignition Coil Perhaps????

ehall

OR, the insulation around one of the battery leads has worn away, and is arching when, under heavy accel., it gets close enough to metal.

brad-cam

I had the exact same symptoms. Turned out to be a crack in the #4 spark plug wire boot of my Magnacor wires. Wrapped the boot with the electrical tape, and problem solved.

Tom M'Guinn

It happened to me twice -- once in an rx7tt and once in the 951. Both times the wires looked fine, and both times the wires were causing the high load stumble. YRMV

Luis de Prat

Not to hijack, but this serves as a bump to the thread, since I'm having the same "stumble & no go" symptoms in my stock S2 after having replaced TPS, FPR, damper, AFM, and several other parts. Still need to check the coil but the spark plug wires look fine.

I'm so fed up with this that the car is going to the official Porsche service center on Thursday.

Porschefile

Always check the plugs. I had lots of stumbling/misfire issues with mine as a result of the plug gap being to wide.

reno808

so what is the correct GAP????

Luis de Prat

This is very interesting. I've been putting off replacing the spark plug wires, but maybe they're shot after 146K miles...

Tom M'Guinn

Yep, it gets hot under there. At 146k, I'd say you got your money's worth out of that set.

brad-cam

Luis, yes, I'd be very very surprised if your wires are still good after 146K. My original wires were arcing through the insulation at 70K miles. Get a set of Magnacor's at about $50 a set. They work well, but are a little dellcate. The boots tear if you are rough with them (ask me how I know :- )).

Alpine951

I have been fighting this issue since I got my car back together 5 weeks ago after a long winter of suspension work, k27, injectors and chips. My car has been stumbling under boost. I got a lot of help from Danno at Guru to figure what seems to be the problem. After various checks he got me to check the wires that are going into the Fuel injector connectors (pigtails). Apparently after 16 to 18 years of age the insulation breaks off on the wires and the two wires short out causing irregular firing of the injectors. I later found a bunch of threads on here about it. In the mean time I wrapped the exposed wires with electrical tape and problem solved.