Truck stalls when cold

Kory Kreisler · March 1, 2018

Help... my 2002 GMC 2500HD runs like crap, won't idle and stalls when its cold. Once it warms up it runs like a top. I've been reading fixing, reading fixing. .. dumping cash and it still does it. NO check engine lights, no codes.. just a truck that barely runs when its less than 40degrees out, and its getting worse.

What I've done. New fuel pressure reg, new intake gasket, new temp sensor, cleaned TB, cleaned MAF and new fuel pump.

Whats next? Thinking maybe new IAC valve (can't figure out how to test them) New MAF... or ??

I need help before I give up, hop in buckle up and drive it into a bridge. its got full coverage after all...

bgbdwlf2500 · March 12, 2018

On ‎2‎/‎28‎/‎2018 at 8:23 PM, Kory Kreisler said:

Help... my 2002 GMC 2500HD runs like crap, won't idle and stalls when its cold. Once it warms up it runs like a top. I've been reading fixing, reading fixing. .. dumping cash and it still does it. NO check engine lights, no codes.. just a truck that barely runs when its less than 40degrees out, and its getting worse.

What I've done. New fuel pressure reg, new intake gasket, new temp sensor, cleaned TB, cleaned MAF and new fuel pump.

Whats next? Thinking maybe new IAC valve (can't figure out how to test them) New MAF... or ??

I need help before I give up, hop in buckle up and drive it into a bridge. its got full coverage after all...

I don't think most people on here or any other site recommend cleaning the MAF, just put a new one on.

Kory Kreisler · March 12, 2018

Wouldn't a MAF throw a code if it was bad? Regardless, I ordered one, time and $100 will tell.

Thanks!

bgbdwlf2500 · March 13, 2018

11 hours ago, Kory Kreisler said:

Wouldn't a MAF throw a code if it was bad? Regardless, I ordered one, time and $100 will tell.

Thanks!

I now see you said you cleaned the MAF. It may be worth while to have the truck ecm reset. I cleaned mine on my 2010 and it wouldn't idle correctly in gear. The engine wouldn't slow down as fast as the truck was and would downshift hard

Kory Kreisler · April 4, 2018

UPDATE: More parts same problem. I reset the computer and the truck ran perfect for 3 days then started acting up again. So I put in the MAF sensor guessin that the computer was being told to change by something I put in the new MAF sensor and reset the computer. It ran great for 3 days and started running like I described above. If it's cold it doesn't want to stay running and stalls out, once it's warmed up it runs like a top.

ANYONE have any ideas what I should try or check next?

XSKIER · April 4, 2018

UPDATE: More parts same problem. I reset the computer and the truck ran perfect for 3 days then started acting up again. So I put in the MAF sensor guessin that the computer was being told to change by something I put in the new MAF sensor and reset the computer. It ran great for 3 days and started running like I described above. If it's cold it doesn't want to stay running and stalls out, once it's warmed up it runs like a top.

ANYONE have any ideas what I should try or check next?

Vacuum leak in the intake that goes away when warm? Do you have a good scanner?

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Kory Kreisler · April 4, 2018

I've tried that, replaced the intake gasket already and it made no difference. I do not have a scanner, although I could have bought one with the money I've thrown at it. How much is a good scanner and is it worth it vs. a dealer diagnostic? I'm thinking that if I brought it to a dealer they wouldn't be able to figure it out unless I left it overnight to cool back off and stall out because it's cold.

sefiroxx · April 4, 2018

Had the exact same problem with 01 4wd Burb. Replaced the IAC, runs like a champ now.

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Kory Kreisler · April 11, 2018

ordered a scanner, should be here tomorrow. I will post results, fingers crossed.

Kory Kreisler · April 17, 2018

I have the torque app, but I'm like my 89 year old grandma and the internet... I don't know what to do with it. Only thing I can see on it is basic stuff I can see on the dash, throttle position and O2 info, but like I said, I don't know what's good and what's bad.

Am I not running the app correctly? I do a diagnostic check and it says "torque ecu does not appear to support mode $06", which I think means that whole neato check every sensor thing doesn't work on my vehicle. Any link to an informative web page for help setting up the app would be appreciated.

It's too GD cold to run the vehicle in the garage long to futz with it much, sleeting now with about 18"-24" of snow coming....

txab · April 17, 2018

Have you got any codes?

Kory Kreisler · April 18, 2018

had a random misfire code when I first put the reader on it, nothing since. No Check Engine Lights either. It's been a great mystery...

txab · April 18, 2018

Does it only idle poorly when cold, but when you're on the throttle it runs well? Have you cleaned the throttle body

sefiroxx · April 18, 2018

Check water temp sensor as well, it might be reading warm (when cold) causing the ecu to think the engine is warmed up.

Kory Kreisler · April 19, 2018

Yes, it does only idle poorly when cold, once it's warm and if you're on the throttle it runs well.

What I've done. New fuel pressure reg, new intake gasket, new temp sensor (2 actually), cleaned TB, new MAF and new fuel pump. If I reset the computer the truck runs perfect for 3 days then starts acting up again.