Rough Idle & White Smoke

[alexoconnell]

Hello Pros! I'm new to the site and new to GMC Yukon's. I just bought a 2006 Yukon XL with 180k for my son. Everything was finw until I dumped a can of SeaFoam in the tank...now if I'm sitting idle for an extended period of time the engine will suddenly start to idle rough (seldom dies) and white smoke starts pouring out if the exhaust pipe! I've been monitoring the water level in the reservoir to see if water in the cylinder(s) was the issue. No change in level for over a week. I also changed the plugs and wires last week. I ran a trouble code scan and get knock sensor, fan relay, fuel saturated vapor, and crank shaft sensor. Could one of the known issues be the root cause? I think it's something else, only because the trouble codes appeared some time after the idle problem began. Is there something else I should be checking i.e. fuel filter, water in the tank, etc.? Any wisdom is greatly appreciated.
Alex

 

[YukonXLPerk]

Did you dump an ENTIRE can of SeaFoam in the tank? That could be your problem. I cant remember off the top of my head, but I do think that you should only put 1/3 of the can in at a time.

 

[alexoconnell]

Yes. Entire can in the tank...

 

[Chiggy]

One can only treats up to 18 or so gallons. I dump two at a time with a full tank of fuel in mine from time to time. My guess is that the Mass Air flow sensor could be screwing up making it run very rich. That would explain a few of the symptoms. OR like the code reader is telling you you have a problem with one of those sensors and it's overcompensating and dumping fuel. Crank sensor I guess could explain it as well, it's not firing when it should and it's firing when it shouldn't

I don't want to say just start throwing parts at it but you can try a new crank sensor and if it doesn't fix it then you can take it back to O'riley's

 

[alexoconnell]

Good idea...thanks. I'll start there and follow up with the outcome.
BTW - great site!

 

[Sho'Tyme]

What's up Alex...the problem I'm having is similar to yours except no white smoke...I've change plugs,wires,all four 02 sensors and maf and still idle problem when sitting still...no issues when driving though ...I'm thinking about going to the dealership tomorrow...just a little nervous on them charging me a lot for something small...I will gladly let you know what they find...

 

[alexoconnell]

Good luck....thanks for the feedback and I'll wait to hear the outcome. Hopefully the damages aren't to severe!!!

 

[Grimes]

Curious to see the outcome of this, if SeaFoam was the cause. I'm actually do for a treatment. I usually run it just above E, put half a tank in, pour 1 can in, then fill it to full. Can't remember if I had any odd issues after that, but I'm almost certain it says on the can to expect some differences on that first tank, and not so much in a good way. Nothing damaging though.

 

[Sho'Tyme]

Took the car to the dealership today ran diagnostic and came back with code lean 1 and lean2...Intake gaskets was the problem...had them replace ...everything should be good now...Hope this helps Alex ...

 

[alexoconnell]

Thanks for the follow up information...glad to hear it wasn't anything too serious. I'm still monitoring my situation, but it seems to have progressively gotten better over time! I could be wrong, but I'm convinced it had something to do with the SeaFoam. I'm not being critical of the product, in fact, I'm sure I'll use it in the future - I do think it may have something to do with the amount or conditions in which I used it. Again, I'm no expert, but that's the only thing that was done different. Anyway, I'll follow up if my theory proves incorrect.

P.S. Great site....the assistance and support provided by its members is unbelievably helpful!