Random stalling rough idle

mmikeman

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Ever since I got my mark 8 97 LSC have had a very intermittent issue where car would stall when turning or when coming to a stop, it would happen randomly in the winter backing out/turning the wheel, but seems to be getting worse now when I run the AC especially, whenever it stalls just starts back up like nothing happened as well, was thinking at first PCV valve, replaced that issue remains, got all 8 new coils + new plugs less than 15k old, new KN air filter, new fuel filter, any thoughts on what it could be? I ran an odb2 android scanner I have (comes in handy) and pulling no codes at all period even when it happens I did notice my voltage readings fluc from 13.0 to 12.1 (all rpms) so not sure if maybe my alt could be the culprit as well since the reading was apparently a fail, someone told me might be the MAF but figure Id pull a code if that was the case, car has also only saw premium fuel with this stalling I'd be afraid to run anything lower
 
Yeah I would definitely say it's your alternator. Your voltage readings are way low. Your car doesn't have enough power to run properly hence the rough idle. When you turn on the Ac, radio etc that's putting a bigger load on the alternator and you have even lower voltage to the point where it stalls. Your alternator should be putting out 13.8-14.2 volts.
 
Check your cam sensor harness (the one behind the power steering tank). My wires were torn at the connector and I had the exact same issues you're having. I chased it forever.. I'll find a pic of where mine were torn.
 
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Oooh! SleeperMark, what do you think caused that to happen?

Do the cam sensor make a big difference in wot performance. I've thought of getting new sensors just to see if it will give it better top end
 
Cam sensor does nothing except to get the injectors firing on time at start up. It has no effect after the engine is running.
 
Yeah I would definitely say it's your alternator. Your voltage readings are way low. Your car doesn't have enough power to run properly hence the rough idle. When you turn on the Ac, radio etc that's putting a bigger load on the alternator and you have even lower voltage to the point where it stalls. Your alternator should be putting out 13.8-14.2 volts.

This.

Make sure all connections/terminals at the battery/alt + are clean.

Get the battery and alternator checked at an auto parts store.
 
Sleeper,I have to add my two cents and thank you for posting this anecdote. This is the kind of problem that will kill your desire to keep a 16 year old car on the road. But, I have a friend with an old Mercedes who thinks $1500 is a standard shop fee, so our cars seem benign in comparison :) Again, thanks for the heads up on what I am sure was a difficult diagnosis.
 
I was just sharing my issue, not saying that's for sure what is wrong with your car. My wires were hardly connecting and it caused my issues. And a cam sensor will shut off your car if the connection is interrupted. A cam sensor either works or doesn't, so changing it for a boost in performance doesn't do anything. If it starts sometimes, the sensor is fine. There is a lot of heat that gets trapped behind that power steering tank, and it dries out the wires making the insulation britle. I would just take a look at it and cross it off the list. I changed out a lot of things before finding this and wasted a lot of money. But hey, I love my mark! So any money spent was well worth it.
 
If your wires are bad, Dorman makes a replacement harness that splices right into the wire. It was like $10 at Oreilly's, I think.
 
Check your throttle body gasket. Mine had a big chunk missing and it seems like the whole system was sucking in air past the sensors so the engine wasn't accounting for it and would stall the car in similar situations to yours. I replaced the gasket with a new one and my problem went away. It's a hell of a lot easier to do that crap on a Gen 2 as well, you don't have to contort your hands and back like on the Gen 1 with anything involving the throttle body.
 

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