engine dies in flight,immediately restarts

manny

Registered User
i have been having an intermittent problem within the last 3 months or so but the prblem seems to be occuring more often with each passing week.1990 5 speed with 165k.engine dies for a brief instance, ranging in length from a fraction of a second(feels like a jerk) to as long as maybe two seconds.it restarts by itself as the inertia keeps car moving forward since it is a stick and engine keeps turning.i have noticed the following when this happens.tach drops depending on how long the engine "dies", when it dies for a fraction of a second the tach drops about 500-1000 rpm instantly. when it dies for 2 seconds tach drops to zero.speedometer doesnt drop at all. also the upshift light turns on when this happens. am i correct to assume that the upshift light comes on when the pcm looses the signal from the crank sensor ? thus indicating a defective sensor? i am probably going to replace the crank sensor but i would like to know if a faulty dis module and/or cam sensor will also cause the upshift light to come on and tach to drop?
 
Yes. You are correct. The HB is the first thing to check out, and then the crank sensor. :cool: The DIS might possibly cause this, but I've never heard of it happening that way. The cam sensor is not very likely the problem.
 
Loss of tach along with engine shutdown is a sign that the EEC has cut power to the motor, which is what it does if it doesn't receive a crank sensor signal. It needs that to keep track of engine timing, without it, bad things will happen.

I'd try and pull codes first, see if anything got stored.

Also inspect the harmonic balancer and the sensor there. You may need to crawl under the car. Feel inside the pully for the big bolt head that should be there.

Upshift light on a 5 speed, I'm not sure what that signifies. That's typical on the auto cars that cranking and no start with upshift light signifies no crank signal.
 
Mike8675309 said:
Loss of tach along with engine shutdown is a sign that the EEC has cut power to the motor, which is what it does if it doesn't receive a crank sensor signal. It needs that to keep track of engine timing, without it, bad things will happen.

I'd try and pull codes first, see if anything got stored.

Also inspect the harmonic balancer and the sensor there. You may need to crawl under the car. Feel inside the pully for the big bolt head that should be there.

Upshift light on a 5 speed, I'm not sure what that signifies. That's typical on the auto cars that cranking and no start with upshift light signifies no crank signal.
if the upshift light signifies no crank signal an auto cars, would that not apply to 5 speeds as well?
 
simply because it may not. The wiring is not the same so ya never know until someone verifies it. The only verified application is with the auto cars.
 
If anyone finds the answer to this question PLEASE let me know. Post it up here. My 89 XR7 5 speed has done this exact same thing a couple times. Engine just dies as though it were shut off, then comes back to life again.

First time it was only a second or two. Then about 2 miles later it did it again and I ended up coasting and pulling over, it did NOT restart. After I was almost stopped, I tried starting it again with the key and it fired right up as if there were no problems.

It did it again about 3 weeks later, exact same thing... died and restarted, then shortly after that it died and did not restart untill I pushed in the clutch and turned the key.

Now it has been about 6 to 8 weeks since it has done it, but it kinda makes me nervous thinking it may just give up and leave me stranded some night. I hate to start throwing parts at it as I can't be sure if the problem is fixed as it has only done it a couple times and there seems to be no ryme or reason to it.


Tracy
 
Like I said, I don't want to just start throwing parts and $$$ at the problem without knowing for sure what is causing it. If manny is experiencing this problem on a regular basis and a new crank sensor fixes it then I will feel a bit more comfortable buying one and puting it in.

I just don't feel like payin' a hunert bux on a sensor then have the car momentarily die on me again a month later. Then I am back to square one and a C-note lighter in my wallet for no reason. Being my car has only done it a couple times and it has been many weeks since the last occurance, I would have no REAL way of knowing if it is truely fixed.

So I guess what I am looking for is a definitive answer instead of speculation.:cool:

Is there any way to test the crank sensor, or is it just one of those "put in a new one and hope it fixes the problem" kind of things?

Tracy
 
What you're asking for is a guarantee. Nobody here can or will provide that. You can pull codes to confirm what I've said.. (you should do that regardless).

But if you need still better assurance, you will have to take it to a shop with sophisticated diagnostic equipment. :cool:
Good luck.
 
Well, I wouldn"t say I am looking for a "guarantee". I just was thinking that if someone was having the same problem as I am but on a much more frequent basis it would be easy for them to determine what actually works for curing it. I.E.---- Car "dies in flight" very often and has gotten worse over the past few weeks. That person replaces the crank sensor (or some other sensor or part) and the problem is now gone. Now I have a good reason to believe this will help me as well rather than just swapping a sensor and waiting another 2,3,4,5,6,or however many weeks it may be to see if it happens again. Considering this individual is having the same symptoms as I am but MUCH more frequently, it would be easier for him to immediately see results -vs- my car that has done it twice over a 3 week period and not since (6 to 8 weeks ago).

I definately know that no one, including a mechanic with expensive diagnostic equipment, is going to give me a guarantee when it is sensor related. I just want to avoid buying parts unnecessarily if I can. Right now the problem really aint too bad on my car, but I don't want it to get that way if I can help it.

Oh yeah... as for codes... there are none. I tried that after both times the car died and got no error codes. :confused:


Tracy
 
Tracy, if your car is dying and then restarting, the DIS module is a very likely cause. That may not be the problem for Manny, but then again he also has the other symptoms of the upshift light and tach acting strangely.

My car suddenly developed a probem similar to yours - ran fine, then died instantly. Started up again later. It was my DIS module (the gray box above the AC compressor, not the coil pack). I had a code for a coil pack circuit failure, but it was misleading.

To test this theory, you could buy a cheap used DIS from someone on this board (racecougar, perhaps? I dunno who ...) and swap it in. 15 minutes later, you're back on the road. See if the problem goes away.
 
Yeah, I have been suspecting the DIS is POSSIBLY the cause. Just kinda hard to know if the problem "goes away" or not being it doesn't do it very often. One thing I was thinking though.... I DID have the dieing/cutting out problem during the hottest part of the year, when temperature outside was above 90° and the car had been driven hard for half hour or more. Temp guage was not reading too high but I have read in the past that high engine compartment temps will/can effect the DIS.

If I remember correctly... the DIS can be tested, so maybe I will start with that. As far as the crank sensor goes... well, I was planning on a new BHJ balancer soon (before the original takes a crap) and had THOUGHT about just replacing the sensor while I'm in there and the balancer is out of the way.

Tracy
 
Mike8675309 said:
simply because it may not. The wiring is not the same so ya never know until someone verifies it. The only verified application is with the auto cars.

In my 5spd SC if I stall it the upshift light comes on and it starts screaming at me. Once its refired it goes away. Thats normal for a 5spd car to do that and doesn't mean the crank sensor is bad. I would suspect a possible failing DIS that is causing your problems, though it would not be a bad idea to check to make sure the HB bolt head is still there and that the wiring for the crank sensor is not messed up.

Shane
 
Check battery connections...

I have seen this before on many cars. Does the car start easily???? Any other issues. I had a bad ground cable and would start and run and all of a sudden (NOTHING)!!!!


Harmonic balancer is a very good start. All you have to do is look at it and see if it wobbles. Any wobble is not a good sign. Replaced mine before it went bad.

Don
 
lube70 said:
I have seen this before on many cars. Does the car start easily???? Any other issues. I had a bad ground cable and would start and run and all of a sudden (NOTHING)!!!!


Harmonic balancer is a very good start. All you have to do is look at it and see if it wobbles. Any wobble is not a good sign. Replaced mine before it went bad.

Don
my car starts easily every time.i replaced the ignition switch about one year ago as it was causing a similar symptom as the one i have now except that everything would die instantaneously, icluding speedo and radio, upon inspection found the switch was separating. and as i mentioned above this new gremlin krept up on me about 3 months ago and has been fairly intermittent but it does it like once every 2 or three days.has never left me stranded and has never died for more than a couple of seconds.and as i mentioned above the tach drops and the upshift light comes on when this happens.there is no wobble in the harmonic balancer and the bolt is definitely there.im just gonna go ahead with the crank sensor replacement on monday when i have time off of work.since i posted this problem a couple days ago, hasnt done it again.and i drive this car 70 miles each day.but as i stated it has a tendency to do it at least a few times a week either on my drive to work in the morning or on my drive home.but i will definitely post back if this fixes my problem.
 
If the crank sensor does not fix the problem focus your attention to the DIS next. I would find a used one that is known to have worked flawlessly cause new ones are costly and would hate for you to spend all that money just to find out thats not whats wrong with your SC.

Shane
 
Mike8675309 said:
simply because it may not. The wiring is not the same so ya never know until someone verifies it. The only verified application is with the auto cars.
well i have a crank sensor that i purchased from autozone for 38 bucks. thers another parts store where i normally get my parts for my sc but they didnt have the crank sensor in stock. is it a bad idea going with the autozone sensor? i still have a bad taste in my mouth when they showed me that "backwards" iac over a year ago. unfortunately, since i dont have a garage, and it has been raining these past couple of days, i havnt yet installed it. also another thing, since i posted the first time about 8 days ago, it acted up on like the 5th day after initially posting. and the following day it did it again, only this time it did not immediately retart.i coasted to a stop. when i attempted to restart it, it cranked over but did not start. i noticed the upshift indicator light was on during cranking. i waited 5 minutes, still nothing. again 5 more minutes, still nothing. was getting ready to call a tow truck. i tried again, and immediately when i began cranking the upshift light went off and i knew the engine would start.sure enough it fired right up after a couple seconds of cranking.so i have a feeling that the same "rule" about the upshift light being on while cranking on an auto signifies no crank signal, might also apply to a 5 speed.can some one provide a definitive answer to this? also i have decided to not drive this car until i replace the crank sensor, since it finally decided to leave me stranded.
 
manny said:
well i have a crank sensor that i purchased from autozone for 38 bucks. thers another parts store where i normally get my parts for my sc but they didnt have the crank sensor in stock. is it a bad idea going with the autozone sensor? i still have a bad taste in my mouth when they showed me that "backwards" iac over a year ago. unfortunately, since i dont have a garage, and it has been raining these past couple of days, i havnt yet installed it. also another thing, since i posted the first time about 8 days ago, it acted up on like the 5th day after initially posting. and the following day it did it again, only this time it did not immediately retart.i coasted to a stop. when i attempted to restart it, it cranked over but did not start. i noticed the upshift indicator light was on during cranking. i waited 5 minutes, still nothing. again 5 more minutes, still nothing. was getting ready to call a tow truck. i tried again, and immediately when i began cranking the upshift light went off and i knew the engine would start.sure enough it fired right up after a couple seconds of cranking.so i have a feeling that the same "rule" about the upshift light being on while cranking on an auto signifies no crank signal, might also apply to a 5 speed.can some one provide a definitive answer to this? also i have decided to not drive this car until i replace the crank sensor, since it finally decided to leave me stranded.
any one have some insight?
 
manny said:
so i have a feeling that the same "rule" about the upshift light being on while cranking on an auto signifies no crank signal, might also apply to a 5 speed.can some one provide a definitive answer to this?

That would be correct right there. I though I posted about that being the case in an earlier post but maybe I am wrong or you did not read it. If you said your crank bolt head is still there and your balancer does not wobble then replacing the crank sensor should fix your problem for good.... atleast till the balancer breaks.

Shane
 
manny said:
any one have some insight?

Manny,

Check the wires going down to the crank sensor. It is very common for them to rub one of the belts (supercharger belt I think) and cause the intermittent type of failure your experincing.

If you have any coolant leaks on the front of the motor, the chalky residue from the coolant can also cause problems with the sensor. Spraying it off with a pressure washer will usually fix it.

Sometimes the sensors just quit working and need to be replaced.

David
 
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