Topic: Cold Start Problem

[Red Baron]

Hi
I am having a problem after starting my Avalanche in the morning when it's been about 10 degrees or lower at night.
The motor starts right up, but then the motor will go to 3 to 4 thousand rpms, then it starts to sputter like the motor is going to die, and it drops down under 1 thousand rpms. then it shoots back up to 3 to 4 thousand rpms and then it sputters.  This goes on for about 5 minutes, and then it stops.  If I try to drive away before it gets back to normal, the rpms stays at 2 thousand and the Avalanche drives funny for the first three to five miles.  No check engine light comes on, I am using the recommended oil weight, and the battery is good.  Does anyone have any ideas of what could be wrong?  Maybe a bad sensor, fuel filter, or cracked manifold gaskets?

[oHIobellboy]

looking at your profile on the side there it says you have an '03. How many miles? Have you ever done a tune up or cleaned the MAF sensor? That's a pretty quick and cheap attack on the problem if that's what's wrong. Another guess is maybe an 02 sensor. We've got some pretty good engine guys here that will have better advice then me though.

[Red Baron]

My Avalanch has 84,000 miles, and I purchased it this last July.  Don't know about the last time it had a tuneup.  I have never cleaned the MAF Sensor, but I will give it a try tomorrow.

[oHIobellboy]

My Avalanch has 84,000 miles, and I purchased it this last July.  Don't know about the last time it had a tuneup.  I have never cleaned the MAF Sensor, but I will give it a try tomorrow.

Here's a little write up on how I did mine.
http://www.chevyavalancheclub.com/index.php?action=articles;sa=view;article=100

[bluedevil]

Not all second hand dealers tune up their vehicles before sale.  If it drives then, it sells.

A good start, ..... a new set of wires and plugs.

[MyBigToy]

It sounds like you are into the idle saver feature, it's overcompensating and then chasing itself, and it can't correct itself.

Has the battery been disconnected or run down to nothing recently? If so, you probably need to do an "idle learn" procedure. Even if the battery has not been run down you might try disconnecting the battery for about 20 minutes, hooking it back up, and then doing an idle learn. You can do a Google search or look around here; I know I've posted the idle learn process on the site somewhere.

[Red Baron]

The battery hasn't been disconnected or run down since I bought the Avalanche.  The dealer could have put a new battery in, before I bought it.  I googled the idle learn procedure, and found a good site with directions that I will try tomorrow.  I will post if that does the trick.
If not I will change the wires and plugs, but I think that the cold wouldn't effect them, but you never know.
Thanks

[bluedevil]

It may not be the wires since you said it runs fine after a few miles.

[oHIobellboy]

It may not be the wires since you said it runs fine after a few miles.

I had an '81 Chevette years ago that didn't like to start in the really cold weather until I changed the distributor cap on it. I just remembered that.

[HenryJ]

The motor starts right up, but then the motor will go to 3 to 4 thousand rpms, then it starts to sputter like the motor is going to die, and it drops down under 1 thousand rpms. then it shoots back up to 3 to 4 thousand rpms and then it sputters.  This goes on for about 5 minutes, and then it stops.  ... Does anyone have any ideas of what could be wrong? ... or cracked manifold gaskets?

Bingo! Manifold gaskets. The stock plastic gaskets seal poorly. On a cold engine they can leak. Once warmed up they seal and the problem is masked.
You can confirm this by spraying injector cleaner around the base of the intake manifold on the cold engine. You will hear the rpm change and the engine stumble. Once the intake is removed you can see the poor seal the stock plastic bound gaskets offer.

Replace them with the steel gaskets. I use the FelPro w/ PermaDryPlus set.

BTW, I tried to blame the EGR valve, IAC valve, Carbon deposits in the TB, etc.

Cut to the chase and fix the intake gaskets. Not too bad a job. Half a day at a leisurely pace.