Rough idle only in cold weather? Please help

[edd112]

My 04 Tahoe has a weird idle when I start it, only happens in cold weather! Never have this problem during the summer months. Once the truck warms up it runs fine, most videos of "rough idling" cars are way different than this. Sometimes it will drop to 500 rpm or lower and feels like it will turn off. Also it's throwing a random misfire code

I have replaced
Fuel pump
Crank position sensor
O2 sensor
Full tune up
Cleaned all fuel lines
Fuel filter
Cleaned MAF


I hope it's not intake gaskets, I've taken very good care of this truck, has 130xxx miles. What could be the problem

 

[Larryjb]

I've had the same thing going on my 02. I put a scantool on it and narrowed it to cylinders 3 and 4. Because the plugs and wires are quite old (perhaps original... I got it used last summer), I'm going to replace with iridium plugs and new wires. If I still get a misfire on 3 and 4, I'll look at coils next.

I would think that a leaking intake gasket wouldn't improve so dramatically with a temperature change. When I saw how the nylon gaskets failed in my 3.8L, chunks of the nylon would give away leaving the rubberized part of the gasket with no support. I don't see a cold/warm engine improving this so dramatically. I could be wrong, though. I've been wrong before.
Larry

 

[edd112]

I've had the same thing going on my 02. I put a scantool on it and narrowed it to cylinders 3 and 4. Because the plugs and wires are quite old (perhaps original... I got it used last summer), I'm going to replace with iridium plugs and new wires. If I still get a misfire on 3 and 4, I'll look at coils next.

I would think that a leaking intake gasket wouldn't improve so dramatically with a temperature change. When I saw how the nylon gaskets failed in my 3.8L, chunks of the nylon would give away leaving the rubberized part of the gasket with no support. I don't see a cold/warm engine improving this so dramatically. I could be wrong, though. I've been wrong before.
Larry[/QUOTE

Yeah it never does this during the summer months. I've had this truck for 2 years and it always has this problem when it's cold outside. It runs like a beast when it warms up though since it has a fresh tune up and clean fuel lines. Always changed oil on time.
I should add that I installed a k&n air filter. Although I doubt that is the problem. My brother has had the same filter on his 04 Silverado and has never had an issue

 

[Jimmy John]

What about the coolant temp sensor?

Here is a good article on them. http://www.aa1car.com/library/coolant_sensors.htm

 

[edd112]

What about the coolant temp sensor?

Here is a good article on them. http://www.aa1car.com/library/coolant_sensors.htm

I'm gonna give this a go, I'll keep you updated

 

[#1taho]

Try spraying air intake cleaner around the intake and see if the idol changes. That will tell you if you have a leak.

 

[sumo]

Also check intake tube. If there is a leak getting by the maf.

 

[Larryjb]

See if you can borrow a scantool and check the misfire history. If you have misfires on just one or two cylinders, that will help narrow down the issue.

I did have a MAF go bad on me once, but it caused the engine to just quit.
I would expect any intake leaks to cause random misfires among all cylinders.
If you have a random misfire on 1 or 2 cylinders, try swapping coils and see if the misfire moves to the new cylinder with the coil.
Also, don't expect new plugs/wires/coils to be problem free. I've been caught on that more than once.

Larry

 

[edd112]

See if you can borrow a scantool and check the misfire history. If you have misfires on just one or two cylinders, that will help narrow down the issue.

I did have a MAF go bad on me once, but it caused the engine to just quit.
I would expect any intake leaks to cause random misfires among all cylinders.
If you have a random misfire on 1 or 2 cylinders, try swapping coils and see if the misfire moves to the new cylinder with the coil.
Also, don't expect new plugs/wires/coils to be problem free. I've been caught on that more than once.

Larry

Still misfires randomly, next thing I'll do is test the MAF

 

[bottomline2000]

Intake gasket...mine went bad when my motor was stock. Sounded like it was cammed.. the cold weather makes the gasket hard enough to create the gap. It would get better as the engine warmed up and eventually run normal. Cold start and repeat..metal fel pro intake gasket is your friend..

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