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Hard stall, now engine randomly shuts off?

whatoctaneiscoffee

whatoctaneiscoffee

now with more caffeine!
Joined
Apr 25, 2020
Location
Maryland
For starters, my car is a 93' 940 turbo. A few days ago my clutch cable snapped as I was coming to a stop, didn't pop it into neutral fast enough and stalled it. Was a pretty hard one; once I pushed it to the side of the road the car would crank over but not start. Replaced the cable on the side of the road, and mercifully by the time I was done it decided it felt like starting again. However, now the engine will shut off while driving, seemingly at random. It seems to happen more once the car has warmed up, but I can't say for certain.

Since this issue started, I've reset the ecu, confirmed that I haven't jumped timing, swapped in a known good crank position sensor. Didn't find any grounds that shook loose. Don't have any lights on the dash. I believe it's tied to ignition - when it dies the tach immediately shoots to zero, no stumbling or stalling. Put it in neutral, turn the ignition and it'll start right back up again and run for a couple more minutes before it happens again. Quite annoying to deal with on my morning commute.

Anyone have any ideas on what else to check?
 
widewagon92 said:
For starters, my car is a 93' 940 turbo. A few days ago my clutch cable snapped as I was coming to a stop, didn't pop it into neutral fast enough and stalled it. Was a pretty hard one; once I pushed it to the side of the road the car would crank over but not start. Replaced the cable on the side of the road, and mercifully by the time I was done it decided it felt like starting again. However, now the engine will shut off while driving, seemingly at random. It seems to happen more once the car has warmed up, but I can't say for certain.

Since this issue started, I've reset the ecu, confirmed that I haven't jumped timing, swapped in a known good crank position sensor. Didn't find any grounds that shook loose. Don't have any lights on the dash. I believe it's tied to ignition - when it dies the tach immediately shoots to zero, no stumbling or stalling. Put it in neutral, turn the ignition and it'll start right back up again and run for a couple more minutes before it happens again. Quite annoying to deal with on my morning commute.

Anyone have any ideas on what else to check?
Click to expand...

Random shutoff during running sounds like an electrical issue. Bet that the shock knocked something marginal loose.

Try wiggling every harness connection you can find under the hood with the engine running, until one of them makes the engine shut off. Then disconnect, contact clean and reassemble securely, possibly with some dielectric grease to keep the water out. Was the distributor Hall sensor on my '87 but that was LH 2.2.

Also check the fuel injection fuse holder if you still have the original one. They get wet, then corrode, then overheat and melt in roughly that order. A decent waterproof rubber one should be just a couple dollars at any auto parts store.
 
The issue could be the ignition amp heating up and shutting down. Or the connection being corroded because it's near the battery. The last car I dealt with this was an 88 760 turbo and it came down to the ignition amp or coil and it was the amp.
 
If the stall was accompanied by a big engine lurch, I am going to go with you pulled something loose and now you have an intermittent electrical connection. Watch what is happening on the instrument panel. What goes black / doesn't work may give you a clue. When you try a restart, does the CEL illuminate? That would indicate whether the ECU is powering up.

I had a similar problem on my 1987 745 turbo. The first time it occurred it was a failing ignition switch causing complete random shut downs. The dash went completely dead with that one. The second time it occurred it was intermittent electrical connections associated with the Volvo bio degradable wiring harness (should not be a problem on a 940).
 
Should've updated earlier. Poked the connector going to the ignition amplifier while the car was running and it shuts off. Took the sheathing off the wires and I don't see any loose connections. Sprayed out both sides of the connector with electrical cleaner and wiped them out, put some new dielectric grease in there, problem persists. I have a new amplifier coming wednesday, in the meantime it looks like I've got some wire tracing to do.

Thanks guys!
 
Since it seems to be mechanical (responds to poking) and connection looks good, also possible that the solder joints between the connector pins and the board have cracked and poking/vibration opens it up just enough to lose ignition.

After you get the spare installed, could try opening up and re-flowing the solder on the old one to try and generate a working spare. Assuming the board isn't conformal coated or potted of course. I've only owned Chrysler ignition cars so never been inside one of those. ;-)
 
I don't know the specifics of the connector on the amplifier. However, assuming it is a multi pin plastic housing remove the plug and check the position of the metal terminals in the plug housing. On occasion, the retaining tab / tang for the individual terminals can be damaged which means the actual terminal is free to move inside the plug body. When you push the plug into place the damaged retainer tab allows the terminal to be pushed back into the plug body resulting in a poor or intermittent electrical connection. This problem could have existed from the original assembly of the car; but, didn't manifest itself until it got the 'jerk' which pulled it free.
 
An update: popped in the replacement ignition module, started the car and tried wiggling around the wires and plug like I did before. Idle didn't budge. Going to reset the ecu and lower my idle speed a bit, but I will cautiously say I think I found the problem. Thank you all for your help!
 
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