Flummonxed: why does my 93 850 stall when warmed up?

[JimBee]

But after resting for about a half hour, starts and runs fine through the day, even with multiple stops and restarts.
Details: Starts fine in coldest weather, once "straightened out", runs fine.

However, if I try to drive it before it finishes with it's fit, I won't get far because when it's warmed up partly or fully, it will stumble and quit and will not restart. until it rests for a while—i.e., cools down for around a half hour— a little longer in warm weather than in colder weather.

One clue: it doesn't always quit if allowed to idle when it's warmed up. But the instant I touch the accelerator, it stumbles and dies.

This is not new, it began doing this a couple of years ago, so I know that even though it starts almost instantly with key turn and seems to br running fine, if I intend to drive it, I need to let it go through the warmup-stumble-rest-restart cycle and then it's fine..

Final note: The stumble and quit seems like gas starvation, it's not instant like an ignition cutoff.

Theories?

[JimBee]

Linguistic puritans will notice my misspelling, haste makes waste!

[scot850]

How cold is it currently? Does it do this all year around or only when it is really cold? If it is only when it is cold it could be moisture in the distributor and worn distributor cap and rotor arm.

It could be the throttle body is freezing. Not common on NA engines if the warm air ducting is in place and the thermostat is working.

You could try the cardboard zip-tied to the inside of the grille (don't run at more than +10C (50F). This channels less cold air into the engine bay and can help if the warm air system is not working.

If you have a prevailing wind direction like we do here, try to park the grille downwind.

There are other possible issues like tired cam/crank sensors and a faulty ECT not 'choking' the engine correctly. Again check it is measuring the temperature correctly and the wiring at the connector by the power steering pump is not compromised.

Lastly, check the relays on the top of the radiator for corroded connectors that get damp and dry out when warmed by the radiator as it heats up.

Good Luck!

Neil.

[JimBee]

Good questions. It's the same year round.
One thing I forgot to mention is it only does this when there's moisture in the air, either from rain at the time of startup or if it had rained over night and things are not dried out—or if there's snow around, even if it hasn't snowed in a while, there is snow near the car when it's parked and that causes the symptom, as well.
If the weather has been dry and there's no snow (other seasons) for at least a whole day or more, it doesn't quit like that, just starts and runs normally.
So it's dampness, moisture in the air that consistently causes the issue.

So, as you suggest, something is getting damp, then when the engine warms whatever it is apparently dries out.
BUT why does it start and run normally until it warms up, then stumbles and quits?

Maybe you remember back in the day, a failing fuel pump, accelerator pump in the carb, or something in the gas feed or air mix, could be overcome by pumping the gas, hand over the carb throat, as the engine struggled and it would straighten out—the stumble I described is sort of like that, but instead of catching and straightening out, it just quits with the slightest touch of the accelerator.

Then like I said after a rest and cooldown no further problem. Even if it's many hours from the first startup and quit cycle, then parked and started later, even if there's moisture around or raining, once it goes through the quit cycle on first startup then runs proper for awhile it's okay until it rests over night—then if there's moisture, same start, quit, rest, and normal restart cycle

Hmmm, hopefully not something related to the LED sensor on the dash that resets something when it gets dark. Although, once it has been running properly, stopping, starting, it's okay during daylight or darkness even late at night.

Thanks for the suggestions: I'll take a look around at the wiring you pointed to.

[erikv11]

I had an NA 850 with a worn cap/rotor pair that was fine until the car got hot. Heat soaked the distributor, car would stall out then not restart until it cooled.

I'd also check cam seal behind the rotor, make sure it is seated. Blown cam seal would bring moisture into consideration.

[JimBee]

Erik, when your 850 had that issue, when it restarted did it run normally after the stall and cool down?

[abscate]

Erik, when your 850 had that issue, when it restarted did it run normally after the stall and cool down?

I went looking for that thread but couldn’t find it….

[erikv11]

Couldn't find it either! I thought I had posted about it when I finally discovered how worn the cap and rotor were. The car was on loaner, to the guy I eventually sold it to. So a lot of it was him telling me what happened.

When it stalled, it wouldn't re-start until you let it cool down. After the cool down it would run fine, until it got hot again.

It also didn't always stall, just sometimes. But it was getting worse and worse when I finally pulled the cap. The rotor tip and the contacts for the cap were in bad shape once I finally looked under there.

Also remember, P80 rotors can go bad internally (really), and look fine. Several cases of that on the forum.

[abscate]

Couldn't find it either! I thought I had posted about it when I finally discovered how worn the cap and rotor were. The car was on loaner, to the guy I eventually sold it to. So a lot of it was him telling me what happened.

When it stalled, it wouldn't re-start until you let it cool down. After the cool down it would run fine, until it got hot again.

It also didn't always stall, just sometimes. But it was getting worse and worse when I finally pulled the cap. The rotor tip and the contacts for the cap were in bad shape once I finally looked under there.

Also remember, P80 rotors can go bad internally (really), and look fine. Several cases of that on the forum.

You did, it might have gotten lost in the WDYDTYVT thread

The OE caps and rotors last a long time on these cars but eventually dust and moisture claim then

5 year replacement is probably the right PM interval. Avoid the sneers from 1999- with coil packs as they pass by in limp mode, the warm glow of the ETS light illuminating their faces

[erikv11]

Okay my first post about this problem was in a bloopers thread viewtopic.php?p=545482.

But I later mentioned it, 5 years ago now, in ... wait for it ... viewtopic.php?t=99001