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Old 10-16-2020, 07:18 PM
Tonyfeb14 Tonyfeb14 is offline
Join Date: Feb 2012
Location: Littleton, CO
Posts: 41
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Occasional white smoke with rough cold idle

My 4.4 2003 X5, 151k miles has occasionally puffed billows of white exhaust, then cleared up. This happened to my wife twice and caused some emergency calls to me to come and get her.

When I got there, the car started, the smoke cleared and it ran fine. She was scared by all the white smoke and thought it would blow up.

Also, I have noticed in colder temps, just starting, the idle is very erratic until the engine warms up. In fact, it hardly runs, surges at idle and needs a lot of throttle correction until it warms up. Anything below around 60 deg is a problem so something is wrong with the enrichment circuit. I would think that points to the ECM.

On the smoke problem, it threw error codes for multiple cylinder misfires, and a load of other downstream catalytic converter problems, then clears up. I thought maybe head gasket or coolant leak would cause white smoke, but the problem clears up and all seems normal. I thought leaky fuel injector, but I figure that is likely one cylinder misfire, not multi cylinder misfires. I was ready to replace the injectors. I have also seen smoke now on startup when it sits overnight, but it clears quickly.

I started to think in might be an ECM problem since cold idle and sporadic smoke could be a fuel injection problem affecting multiple cylinders.

Out of curiosity I made the mistake of trying to clear all the adaptions in the ECM with my scan tool (because the tool would let me do that) and that just about did me in. It stalled, I got engine malfunction errors on the dash, and it hardly ran at all, lost the throttle response all together, lots of smoke, surging idle. I thought next stop was call a tow truck. Finally, after trying that again and shutting down and restarting, at least it is running again and I have throttle response. But the cold idle is still horrible, now maybe worse, until it warms up. And its not really that great when operating temperature, but a least idling around 750 rpm with a slight drift up and down.

Any ideas? I am leaning towards and ECM problem, and thinking of sending it out to have it tested and repaired. Buying a used 17 year old ECM on Ebay doesnt sound very attractive. There is a place that advertises for $200 they can fix an ECM.

But before going that path, thought to check on the forum for any ideas on what else to check. Always good ideas on this forum so asking to share some wisdom about this beast before I go much further on the ECM.
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