Cold Weather Problem

[wilkes65]

I have a 2001 GMC sierra 1500 z-71 and when the temperature goes below 50 degrees or so it misses real bad when I first start it up in the morning. When it heats up it goes away. I have changed the plugs and wires and it did not fix it. I have 150,000 miles on the truck. What do you guys think? It is definetley temperature related because in the summer time there is no problem.

[ws6_guy]

running real thick oil all rear round? best to change to a lighter weight in winter since the temp cant really over heat the engine

[drew28]

I know its off topic and this won't help but I miss when 50 degrees was "cold weather" . gd luck

[LF Motorsports]

Best guess it's electrical. Might try replacing the cap and rotor. And at 150k, it may be worth changing the ignition module (if this is like the older trucks) because your already half way there.

 

Coil/coils usually don't work when they get hot, not cold. So likely not the coil.

 

Lance

[pm26]

I know its off topic and this won't help but I miss when 50 degrees was "cold weather" . gd luck

 

Maybe he meant "less than -50degrees".

[BowTieDude]

Best guess it's electrical. Might try replacing the cap and rotor. And at 150k, it may be worth changing the ignition module (if this is like the older trucks) because your already half way there.

 

Coil/coils usually don't work when they get hot, not cold. So likely not the coil.

 

Lance

 

A 2001 wouldn't have a cap or rotor to change (no distributor) unless it had the 4.3 V6, which isn't likely with a Z71.

 

Maybe the egr valve is sticking open just a tad. Seen that before on other cars and they'll miss like crazy when cold. Is the service engine soon light on? Have you had the computer checked for codes?

[wilkes65]

Yeah , the service engine light has been on for years now. It is the knock sensor that makes the light come on. ( I don't plan on taking the intake manifold off to get to it ) What exactly is the EGR valve and is there a way to check it?

[wilkes65]

Well like clock work this morning temp was 52 degrees and it idled fine. Anybody got any clue where I should start with this problem?

[Bostonsfavson]

The EGR (exhaust gas recirculation) valve is an important part of the truck's emission controls. It recirculates a portion of your exhaust and runs it through the combustion process again, helping engine efficiency and reducing harmful emissions. Considering the problem that you're having, I doubt that the EGR valve is the culprit. I'd be more inclined to suspect whatever type of idle control your engine uses. Also, a simple thing that you may want to try is cleaning your throttle body/MAF sensor. It's not very difficult, and doing so will be beneficial even if it doesn't solve your problem. It's definitely worth a try.

[wilkes65]

Thanks I will try that.

[thymer]

I had a crappy idle when cold outside and a knock sensor CE code along with a lean condition code. My intake manifold was leaking. Pulled the manifold, replaced the rusty knock sensor (and did the tsb to prevent future failure) and put on new gaskets. Runs like a dream now.

[krzykjn]

My '99 did the same thing! I changed the TPS sensor ($43.00) and cleaned the Idle control motor and butterfly flap. Cleared all problems, idle great now!