Ambient Temp Stalling Issue
Chasing this issue for 2 years now with my 190e. When the car is in closed loop and the ambient temp is low-70s and below the car will randomly stall when braking. Honestly it does not happen mid-70s and above which is super weird to me and makes it really hard to track down, can only test in the fall and winter. I can't really reproduce it either, just completely random.
Anyone have any ideas, IACV has been replaced? |
Interesting issue. For a car to stall you need to either lose fuel or spark or both.
What I would do: Wire up one volt meter to the fuel pump and the other one to the ignition coil and put them in the interior. When the stall happens just observe what they say. Then I would start diagnosing further Also - Year? 2.3? 2.6? |
Sounds like a manifold vacuum leak. Cold weather exacerbates vacuum leaks and CIS systems are very sensitive to them.
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His car stalls when braking and when the engine is warm. More like an intermittent bad contact. |
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89 2.6
I have had an intermittent hard start the whole time as well, hot and cold weather, always starts on the second turn, but hard starts seem to be the norm on these. No idle issues though. I've been meaning to try a smoke test regardless so maybe I'll start there. I also haven't tested the fuel pressures which is also on my list. |
I haven't had a chance to do a smoke test yet, but I had another stall today which is an oddity. Backing into the garage, using the brake to regulate speed annnnnd stall. Would a vacuum leak still be a likely candidate here?
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Booster line seems to be in good condition, definitely not original, nothing obvious that I can see.
That said, this only happens once the car is warmed up and in sub-mid 70s temps. That engine is HOT by the time it hits operating temp. What possible effect could the cold air outside the car have on the vacuum lines. Even if there were leaks, the engine bay temp is the same in August as it is in December when the cars warmed up. |
I am going with the vacuum leak theory, and there may be associated other faults as well such as brake booster leak, O2 sensor, air temp sensor. The brake booster "consumes" vacuum when you press the brakes. Just as a test, I would try pressing the brakes multiple times (when you are standing still, not driving) when the engine is warm (and running obviously) on a "warm" day. See if you can recreate the stall without the air being "cold", just by using the brakes more. It might provide a clue. Or maybe not.
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The air flow potentiometer can cause stalling when braking to a stop. Check the voltage on it as deflecting the plate. An open spot near the zero position will do it.
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I’ve never been able to replicate it consistently. Has never done it while idling. It has happened when when parking at a high steering angle, not sure if that’s coincidence or the extra load on the power steering has caused an increased chance of it happening, however it’s happened with no load on the power steering as well.
Pouring down rain today so I’ll do some potentiometer testing tomorrow. |
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Only when braking. It actually happens coming out of decel, when the ecu is looking at the potentiometer voltage to set the idle valve position. If potentiometer voltage drops below the lower threshold (somewhere around .4-.5V IIRC) it assumes a stalled engine and doesn't even try to catch and idle it. When checking the potentiometer voltage, its this lower voltage range that must be smooth and linear. A glitch at 2V isn't going to cause this problem, but if it goes open somewhere around .5V-1V you've found your smoking gun |
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