Hello all,

I have been battling an ongoing problem with this car where it will start barely, or start and idle for a momment and then die. Other times I will drive and suddenly lose throttle response. Stopping the car and restarting it seems to help some of the time. Sometimes the car simple corrects itself and keeps going. Runs perfect for two days and then like crap one day. I can get the car to run, but it won't rev above 2K, and the revs oscillate at that point. I have replaced the RPM sensor, FPR, fuel and radio suppression relays with all new. Also the dealer replaced the fuel filter about a month ago. The car is right full of gas. Car has 165 kms on it. I have cleaned most connections under the hood including AMM, TPS, knock sensor, RPM sensor, and power stage. When the car is barely running, if the tank pump fuse is removed, the car will die. So I am thinking perhaps problems with the sock or tube on the tank pump, like Brandon at FSU had posted recently, or could still be electrical. Have had code 3-1-2 on OBD for FI, but usually no codes. Control unit is 563 Jetronic. Have new plugs, wires, cap and rotor ready to go in if I can get the car home.

Driving me up the wall, and I need a reliable car for work and travel.

Any ideas. Car will not run well enough to drive at the moment, and is stuck at store parking lot 25k away. Will try again tomorrow, or to the dealer on the hook it goes.

A beautiful car, yet such a pain in the butt!

Again, all information and advise is appreciated. Thanks in advance.

Sean

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91 740T M46

Sean..i lost the powerstage in my 91T a while back..what u need todo is meter the plus to the coil when the car is failing..this line comes from the powerstage..if that is all good..a while chance is your cat/converter partial block or broken inner core..this cause hard starts and low RPMs...goodluck

Try replacing the coil. Turbos get hot enough under the hood for this to be something of a likely failure. I don't know if you could find a used one today, but it's worth a shot. Call the junkyards. I personally got left high and dry by an aftermarket coil so I will not recommend one. I'm sure there are Autozone coils that will fit and work, at least that would rule that out.
If that doesn't do it, get the fuel pressure tested.
The spark plugs look ok? Check them all.
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Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE, 91 244: 808K total

Do coils half die? I looked at the resistance of it, and it was a bit low, but this was with an analog meter. I can't get the boots off the plugs! Pulled one wire off the connector, and have a new set to put in. Symptoms of the car have not changed. I know at one point in time the #4 plug looked much worst than the rest of them.

Thanks for the advice. I'll try to get it going again tomorrow.

SC
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91 740T M46

Does it do this when the tank is full? If not, then suspect the in-tank pump or hose/sock.

As mentioned, the tank is completely full. I usually don't run it down past 1/4 left. The tank pump sounds very happy. I don't know if this means that it is doing it's job or not. The fact that if I remove the fuse for it while the car is "half" running, and the car dies, points me to the sock and tube scenario...I think.

SC
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91 740T M46

Hummmmm, Well my 87 did the same thing a while back and it end up being a bad power stage. It also did it when the engine wiring harness went bad. This is the one that runs under the throttle body and lays on the engine block. Both problems can be attribited to age and heat under the hood. At 250k I just got fed up with little nickel and dime problems and replaced everything. The distributor, the power stage, amm, coil, new brushes and voltage regulator, and all the relays. It was the best $600 I ever spent. Now at 278K it runs like a champ and I have no fear of the car dieing at a bad time.

Yes, this is where I'm thinking of going as well! The wiring harness issue is isolated to cars up to 87 is it not? Power stage is definitely a possiblity. Your distributor has the Hall sensor as well correct? With the RPM sensor on my car, I'm hoping a cap and rotor, wires and plugs will eliminate this side of it, with exception of the coil and power stage. Then it's on to fuel side!

I need that no worry reliability back!

Thanks,

Sean
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91 740T M46

this may be a complete irreelance..but on a car i once had (not volvo but..) the power stage used to lunch itself every 50k or so...(started going this at about 200k...(thats miles by the way!)..It was interesting in that it was sort of temperature related...would be fine for a bit, then on a longish run would (sometimes) just die (or run like a bag of sh*t - then die) leave it a while it would run again for a bit (i.e. a few miles) then die...leav it overnight it would be fine!

In the end i just carried a spare stage in the car....(about £50 each i remember)...car went at 300k due to a head gasket and it just wasnt worth fixing...

Certainly my experience of power stages suggests the fail in 'interesting' ways, but then again so coils! ...also have you checked (i.e. REMOVED each of the main battery/body/engine earth straps - I have seen 'interesting' problems due to osrrosion under these...hell its cheap and easy so why not strip them out anyway - elliminates one more thing...