TPS? - Intermittent #5 misfire, stabilitrak and traction conto

[m1dn]

Was driving home and decided to have a visit at touchless car wash that also pressure sprays bottom of the car.

About a mile or two after car wash i get Stabilitrak err, Traction Control err and engine light blinking.
Also limps, we get on highway and while cruising at same speed, lights go off in few minutes.
I accelerate and lights go on again, rough idle.

Got home safely and reader says pending cylinder #5 misfire.
I erase the codes and when idling with gas you can feel misfire at about 1800-2000 rpm only and all 3 symptoms come back.

Engine sounds fine, just rough idle.
It was intermittently having rough idle before that too.

Cleaned the throttle body and mas before, all wires and plugs are new, coils are old though.

Google leads me to tons of similar threads where TPS seems to be causing all 3 issues, anyone had anything similar?

Not sure what else could possibly fire off all 3 issues…

 

[m1dn]

While researching all these issues with TPS and similar bugs i found out some folks saying water gets into sill under the door where the harness for body to tp is and the moisture makes it go nuts.

Could be why it happened after the car wash.
Taking the sill off tomorrow, drying out and checking if it helps.
If it does, adding dielectric grease and trying to find out how the hell water got there.

Oh also probably replacing TPS anyway, maybe helps with rough idle..

 

[Geotrash]

Let us know what you find! Didn’t know about that issue.

 

[wjburken]

I’d double check your plugs and wires and if all seems fine, swap one item at a time with another cylinder and see if the problem moves with the swap. Start with the plug, since you’ll have it out to look at it. (Yes - new plugs can go bad). Then the wire or coil.

 

[OR VietVet]

Might want to check the grounds under and back of engine that feed the grounds to injectors and coils. Spraying under pressure may have caused a problem. It's a shot. Especially if you live in a salt area. Have seen a cylinder effected before on a HEI ignition system from car wash spray.

 

[m1dn]

This morning i cleaned error codes and truck ran smooth without any symptoms anymore.

Checked under sill, no water or broken wires.
Noticed i have dangling open plug for running boards that are no longer there, cleaned it up and hid it away.
Checked all other connections that could get water, around fuel tank area, added dielectric grease where i could and checked for any damage.

Not sure what it was, but going to replace tps and see if i get the symptoms again

 

[OR VietVet]

Whatever it was, did not like that water spray. In salt areas I get why people do that when getting a car wash, but man can it cause a headache. What brand of plug wires do you have on the engine?

 

[m1dn]

Whatever it was, did not like that water spray. In salt areas I get why people do that when getting a car wash, but man can it cause a headache. What brand of plug wires do you have on the engine?

Plugs are NGK and Wires are “Standard” both from rockauto

 

[OR VietVet]

IMO, plugs are ok but those wires? Genuine GM all the way. I would have looked up those wires but I just noticed that you supplied no vehicle info. Frustrating.

 

[m1dn]

IMO, plugs are ok but those wires? Genuine GM all the way. I would have looked up those wires but I just noticed that you supplied no vehicle info. Frustrating.

Ah sorry, it’s 2008 yukon xl denali awd, should update my signature!