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Wipers causing engine to die?!?[ALL/1998] posted by Jim Seaman on
Wednesday, 20 August 1997, at 6:02 p.m.
Hello again. My "new" car ('91 744t) is having a strange problem. When I bought the car, the wipers and horn did not work so I had the dealer investigate and they found that the fuse was missing. They replaced it and I tried both the horn and wipers and they worked so I bought the car. Today is the first time that I have had to use the wipers for any lenth of time. After having them on intermittent mode for about 20 minutes and while on the freeway, the engine started cutting out. It would run at a steady state with just a slight amount of throttle but if I gave it any more it would cut out completely. I coasted to the side of the road and tried to figure it out. It would run (albiet raggedly) at idle but when given gas it would run -cutout -run -cutout run -cutout (kind of like running into an rpm limiter). The only thing that had changed was I was using the wipers. I shut the wipers off and removed the fuse. The car restarted and ran raggedly but I was able to accelerate back to freeway speed and within a moment ran like normal. I can't imagine anything that could cause this as the only things that appear to be on the circuit are the wipers and horn. Has anyone seen this before? I live in Seattle so wipers are kind of nice to have......
Thank you in advance for any and all advice.
Jim
Re: Wipers causing engine to die?!?[ALL/1998] posted by Robert on
Wednesday, 20 August 1997, at 9:48 p.m.
Jim,
I have seen ws wipers cause a 240 to run rough and stall. The wiper linkage had rubbed through the fuel pump relay harness. This probably could not apply to your car. I seem to remember something like this on a 740 that was caused by a bad ground behind the headlights. Most likely your problem is not related to the ws wipers. If the power surges follow a set pattern, here are a couple possibilities. A broken hose to the turbo's waste gate will allow an overboost condition. This shuts off fuel until the boost drops, then turns on again. This causes an on-off feeling.
If the fuel ECU sees a closed throttle signal while above 2100 RPM's, the computer thinks you are decellerating. It turns off the fuel injectors until the RPM's drop below 1700. At this point the injectors start working again. If you had a defective throttle switch or one of it's wire shorted to ground, you could have an on-off situation again. If it happens again, see if the boost gauge is going into overboost (not likely to be intermittent). See if the RPM range fits what I described above. If the on-off doesn't have a specific pattern, it could be several other things.
Gather as many details as you can if it happens again.
Robert
Re: Wipers causing engine to die?!?[ALL/1998] posted by Jim C. on
Wednesday, 20 August 1997, at 10:18 p.m.
Check the grounds connections on both front fenders, just behind the
parking lights. One of the spade terminals may be loose or disconnected.
Jim C.
Re: Wipers causing engine to die?!?[ALL/1998] posted by Jim C. on
Wednesday, 20 August 1997, at 10:24 p.m.
Check the grounds connections on both front fenders, just behind the
parking lights. One of the spade terminals may be loose or disconnected.
Jim C.
Re: Wipers causing engine to die?!?[ALL/1998] posted by Jim Seaman on
Wednesday, 20 August 1997, at 11:16 p.m.
Robert and Jim C.
Thank you for the information and quick responce! I drove home tonight in an extreamly light drizzle with the wipers on intermittent again, roughly over the same route. The problem did not recur, but I checked the grounds behind the headlights when I got home. Both sides were slightly corroded but not really badly. I cleaned them up a little just to be safe.
Robert:
When the problem occured I was on the freeway at about 3,000 rpms. The car would run slightly if I was decelerating but would stumble badly if I floored it (ie: the engine would seem to trip and fall on itself and not recover untill I had eased up on the throttle) I do remember what the boost guage was doing as it did have unusual behavior, it would rise and fall with my right foot but not into the red. The reason this seemed so unusuall was because as the boost rose the rpm's fell. I am sure that this is alright but it was different than I am used to seeing> rpms go up and boost goes up. On the side of the freeway, it did not idle very well. At about 1200 rpm it would cut out and die completely unless I released the accellerator. After fooling around with the fuse block (at least they put it in a convenient place) and removing the wiper/horn fuse I restarted the car. It did not run well but I was able to accellerate up to speed and by the time it reached 4500 rpm it acted as if nothing ever happened. It may have just been coincidence that the car did not have a fuse in the wiper/horn location and that it sort of corrected itself after I pulled it especially since I could not duplicate it in over twice the amount of time and miles on the way home. I tried to make the electrical load as close as when it happened as well (no lights and intermittent wipers.) I like the ground theory as it might explain my speedometer problem that mysteriously fixed itself the other day. I guess I wait and see what happens since I cleaned the grounds unless you have any additional advice. (I am actually desparate to try just about anything since I really need a dependable car)
Thank both of you for your help!
Jim
(Wiperless in Seattle?)
Re: Answer! Wipers causing engine to die?!?[ALL/1998] posted by Jim Seaman on
Tuesday, 26 August 1997, at 8:38 p.m.
OK, the answer is: The wipers were just a coincidence. Also coincidental was my removal of the fuse and the car's return to runability. The dealer found a bad crank rpm sensor and a bad air flow meter. $600 later I think the car is fixed (?) I hope(!) Thank you for your help!
Jim