Date: 05 Dec 1999 16:25:12 GMT
From: Dave Wysocki <>
Subject: Re: Fuel injection 86 900

I had something similar on my '84 900 S, which turned out to be a thermally intermittent hall-effect sensor in the distributor assembly. Of course, the problem happened very infrequently (at first), and usually on the highway when the car was hot. The tach would drop to zero (even though the engine was still turning while the car was rolling, which should have been a clue), and the engine would sputter or shut off. Sometimes it would restart in a few seconds, as I was pulling off the road, but letting it sit & cool down for a bit would otherwise get it going again. Driving with the hood unlatched (so that air was blowing on the distributor) seemed to make it run better. I first replaced all the obvious stuff - ignition control module, distributor cap & rotor, and the coil. There wasn't much else that could cause this other than the hall sensor, and a $75 used distributor assembly fixed it. That was about 250,000 miles ago - the car is now up to 400K. Dave Wysocki '93 9000 CSE '84 900 S Message by Benton Quest <> on: 12/5/99 1:56:12 AM >SYMPTOMS: This is a really weird problem that this car has had for 2 years. >Originally the engine just died. I just pulled over and waited a bit and it >would restart. After checking the fuel pump and finding it okay, I >determined that for some reason, the fuel pump relay was getting a command >to turn off. > The first start in a cold morning is fine, and sometimes the car will >run great for days, but sooner or later, it will have a “spell”. A spell is >how I describe the condition this car gets sometimes, which seems to be a >very lean mode, as if the fuel pressure regulator is being told by the car’s >“brain” to reduce fuel pressure. The car will go in to or out of a spell >very quickly, in the blink of an eye, and sometimes a spell will stop at the >same time the tach starts working again. > The tach is another mysterious factor in this condition. One minute the >tach works, another minute it is dead. Sometimes the tach turns on and off >with the turn signal, but usually not. If the car is having a spell, the >tach is always dead, but if the car is running fine, the tach may or may not >be working. > There is nothing that causes a spell for sure, and nothing that cures >one. The car seems to have a mind of its own. You can be cruising the >freeway with the car running fine, and then you exit and stop and the car >stalls. Sometimes revving the engine a little brings the car out of a spell, >but usually not. > If you are on the freeway with the engine up to operating temp and the >car has a spell, you can keep cruising, just shift down to 4th gear and >floor it, you can at least stay above 50 mph. But if the car has been >sitting for a while and is nearly cold, and you start it and it has a spell. >You will hear some back firing in the intake manifold. It might snap out of >the spell, but if not, you will have to rev it hard to get enough power to >move, and then only very slowly! > You will get some dirty looks from other drivers as you go thru the >intersection like you are running on one piston! HOWEVER, just floor the gas >until the revs get high enough, and you feel a burst of power, then shift up >and floor it again until that high rpm burst of power comes back. The brain >seems to give some fuel pressure at high rpms even during a spell. Revving >it may break the spell, and if so, then it goes back to normal power. > I suspect it could be either the brain box, the ignition pulse amp, the >amp, the regulator, or a ground somewhere. > Anyone else had this problem? > > > >

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