note re: the coolant temp sensor, the dashboard gauge uses a seperate/different sensor than the one the ECU and ICU use. but I doubt a CTS (coolant temp sensor) problem would cost stalling and failure to start.

 

Just for clarity, I haven't yet had a "no-start" condition. The engine dies, but will then reliably restart, almost always on the first try. Today's driving suggests it doesn't die if the throttle is open, but I'm not yet sure that's always the case.


Is there a test for the power stage? My normal practice would be to go to Pick 'n Pull (I'll be returning a IAC for credit next trip), get one off a wreck, change it out, and see if the problem changes or goes away. If not, I make a working assumption that the component isn't the culprit.


The stage 3 diagnostics on the car (push the test button three times to initiate the injector/AIC/cold start injector/fuel pump test cycle) show up no abnormalities with the mechanical operation of these components. But that doesn't confirm either spark or fuel pressure.


I'm off for the weekend in my 2000 V70, and will follow your helpful leads on my return. Thanks again.

 

stalling at a stop could be as simple as a sticky idle air controller. if it was due to an overheating power module, I wouldn't expect it to start right back up until it had a chance to cool.

 

Before heading out for the weekend, I was able to return my Idle Air Controller to Pick-n-Pull, and pick up a used Power Stage from a 1991 740. After installing the "new" one, I idled the engine for 5 or 6 minutes, then drove out on local streets for about four miles with no problems. Then I did some more errands, for a total of about 15 miles in five trips, with no stalling.


It looks good so far, but I'll do some more definitive tests when I get back, including a longer drive, checking for recurrence of the code, and switching back to the old Power Stage to see if the problem reoccurs.


Lev -- it does look like a weak Power Stage as you suggested, and hopefully I'll confirm that early next week in time to take my 780 to Monterey on Tuesday!


Now a question for the experts: what causes a Power Stage to weaken or fail, or is there any way of knowing?

 

the power stage is basically a bigass power transistor, and takes in control pulses from the ICU and switches the power to the coil. think of it as an electronic equivalent of breaker points.

it fails due to age and heat.

 

Update for me.
The car died again today. I think I found the problem though. Last time and this time I found water in the coil plug where it connects to the distributor. This may be the fault. The first time it stalled it was pouring rain. This last time it poured rain the day before, but I didn't drive it until today. This may be the cause of the issue for me.

 

our 400K mile '87 240 became unreliable when it got damp INside the car. water leakage was condensing on the wiring in the interior in the cold dank winters of Arcata, and it stopped running. daughter got it home, and took the Camry back, I dried out the 240, and it runs fine. sigh, it still needs a brake job, and front lower control arm bushings, and we don't need it anymore, we have too many cars, but thats another story.

 

Update following my trip to Monterey this week.
1. Salmon fishing was a complete bust.
2. My 780 turbo ran superbly with the junker replacement Power Stage. Never missed a beat in 250 or so miles, and delivered 21 mpg. I even took the scenic (coast) road home and used the opportunity to adjust the cable to lower the upshift speeds on the transmission. It now runs like a dream!
3. Next step will be to explore (on a different thread) how to fix my cruise control which in the course of this work has stopped working.


Thanks Pierce and Lev for your invaluable assistance!