Motor shuts down intermittingly

[Bruce M]

Hi All - i'm back!

1994; 3.2L, ATX. No Access to codes yet, but will tomorrow AM.(My son has the car right now)Car runs great for long and or short periods of time. Even got a sticker. While driving at any speed, it doesn’t matter the engine will just shut down just like if you turned the key off. Pull over and it just turns over and over. Wait as little as a few minutes or as long as a day and it will start up and run great again. Idles nice and runs smooth during these periods of time when it is “running” CEL comes on just before this happens. Fuel pump can be heard and there is fuel at the intake.

I have been working on these SHOs for years now and I have heard of this situation but I have never had it happen to me until now.

Where would you look first, CPS it would just die. Bad ground? Bad DIS? MAF intermitting? Clogged fuel filter?

Any help would be appreciated.

 

[LOUDSHO92]

Sounds like the water pump is leaking on the CPS and causing it to go out.

 

[OldShoGuy]

I've had the same experience with my 92 and a friend's 89. Same symptom. Both cars manual transmission so we could see another clue: engine still turning while coasting to a stop, CEL on, tach reading 0. Not sure on an ATX if you can see unusual tach reading.

Anyway, both cars fixed by replacing the crank postion sensor. If you decide to replace it, I would throw a cam postion sensor in at the same time. Both sensors are relatively inexpensive (O'Reilley's is where I got mine). It's a job that can be done by a home mechanic, but it's no small task. Lot's of stuff comes off the front of the engine and the crank bolt can be a booger to get loose. A common trick for that is a socket wrench jammed against the frame and bump the starter. That worked for mine, not my friend's. We had about 6 feet of leverage (pipe added to the socket) and plenty of grunting when the bolt finally came loose.

This is also the time to consider changing the timing belt and of course, the water pump if there is any leakage.

 

[naval-avi8or]

Fuel at the rail and fuel pressure to run are to very different things. Could be CPS, fuel pump or DIS. When the car is in a no restart condition short the fuel pump test port and check fuel pressure. The fuel pump and CPS symptoms are easily interchangable so you need to troubleshoot them vice just thro parts at them. CPS can sometimes be checked by cranking engine and monitoring the tach for several hundred rpm. This doesn't always work but its a start. there is a DIS test procedure on pheniox sho website.

 

[ShadetreeSHOguy]

Sounds like the water pump is leaking on the CPS and causing it to go out.

+1 on this on here, time to do a front 60k!

 

[93rev2sev]

Sounds like the water pump is leaking on the CPS and causing it to go out.

+1 on this on here, time to do a front 60k!

+2 Everytime (3 to be precise) that has happened to me it was front 60 time on a car I had just bought. The last time got me rear ended. It stalled at a light and I was moving but barely...WHAM! I never even saw her because I was watching/waiting for the tach to jump so I could goose it. The next thing I know I'm in the backseat and I realize im moving about 30. Not fun. Don't let that happen to you...unless its an ATX. Those rear end ATXs make great donor cars.

 

[Storm-Chaser]

Hi All - i'm back!

1994; 3.2L, ATX. No Access to codes yet, but will tomorrow AM.(My son has the car right now)Car runs great for long and or short periods of time. Even got a sticker. While driving at any speed, it doesn’t matter the engine will just shut down just like if you turned the key off. Pull over and it just turns over and over. Wait as little as a few minutes or as long as a day and it will start up and run great again. Idles nice and runs smooth during these periods of time when it is “running” CEL comes on just before this happens. Fuel pump can be heard and there is fuel at the intake.

I have been working on these SHOs for years now and I have heard of this situation but I have never had it happen to me until now.

Where would you look first, CPS it would just die. Bad ground? Bad DIS? MAF intermitting? Clogged fuel filter?

Any help would be appreciated.

Bruce - I thought you had a white Gen I ?

You need to watch the tach when the engine dies or will not start. Failure (in this case shorting) of the CPS results in loss of the CPS signal, which is the source for the tachometer readout on the instrument cluster. (this is a very simplistic explanantion, as the tachometer signal is actually based on a subsequent feedback signal, which is derived from the CPS signal)

If it's the CPS, the tach should drop to zero rpm, and trigger the Check Engine Light. The rpm will also register (remain at) zero rpm during that period the engine will not restart. Once the CPS short clears (eg. water on the CPS evaporates due to engine heat), the tach will register rpm and the car will restart.

I have not had a DIS fail. I do know that when the DIS harness connector (black connector at the back of the DIS) is disconnected, the car will not start. Thus you can verify it is the CPS and eliminate the DIS once the engine starts again, by then pulling the DIS connection and cranking the engine. The engine will not start (no spark), and if I remember correctly, the tach will register rpm as the engine turns over.

While the three remaining potential problems you identified (bad ground, MAF, fuel filter) can result in varying engine-running problems, none are likely to generate the off-again/on-again problem you're experiencing, not to mention why the engine will subsequently start as if there's no problem at all.

 

[Bruce M]

Thnaks Storm-Chaser

Hi

I did have a pristine white 90 MTX that I gave to my son; he pried it away from me. I still have a white 93 that I use as a run-around-car. I’m looking for another nice 89 – 92 for a project car for this winter.

The SHO in question i.e. intermitting motor shut down is one that I sold a year ago to a friend. I bought this car did very little to it then sold it for short money to a guy who wanted to work and learn on it. He and my son were out last week and this issue rose twice. I looked at the SHO on Saturday and found high impedance from chassis to negative battery and high impedance from DIS pack plate to chassis and negative battery. We are talking about 20 ohms, which should be 0. The MAF had leaves and partials in it as well as a very dirty Air Filter. All the plug wells are full of oil. I told the owner to clean out the wells, clean out the MAF, clear up the bad grounds including the one on the intake rear passenger’s side. I pulled the codes and found nothing telling. No CID identification fault or anything pointing to the CPS. It did indicate that there was poor EGR flow which is probably clogged ports. The car did not shut down for me during my hour and a half on it. The CEL did flicker during a test my computer asks for which is “depress the throttle and release: I attributed that to EGR as you are “decking it.

I believe that you are correct in your analysis suggesting the CPS. But I wanted all that other stuff out of the way before I helped him strip down to the CPS. Moreover I never asked if I fact the tack remains idle during these shut down periods, I’ll have to ask. He did mention that it seems to occur more often when the gas tank is below ½ full. I could not draw up any coloration there can you?

Thanks Storm-chaser your good with these SHO money gobblers!!!

 

[Storm-Chaser]

Bruce, :wave:

Are you going to the convention? Thought you might like to see that $400 MTX I picked there in Duxbury last September. I was planning on driving my 500,000+ mile SE to the 2009 convention, as Rhode Island is the only state in the lower-48 I haven't driven it in/through . . . .

Hey, want to check-out another 95 SHO for me in the Plympton area?

 

[Bruce M]

Re Plymptom

HI
Is that you Kieth? Let me know where the SHO is, I'll take a look at it
Bruce
Sent me youe contacts ie phone, email

[email protected]

 

[USHOMEISHOU]

CPS!!!!GUARANTEED

I had the same problem on mine, the car would run fine most of the time and every now and then dead, no spark, crank and crank with nothing happening.

once the cps would cool down a little the car would start right up, after a while it just gave out all together (it would only run for about 5 minutes then die and not start again for at least an hour.and then run for 5 more minutes)

turned out, when my CPS got warmed up it would stop sending a signal and the engine would shut down.

replace the CPS and you'll be cool