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Problems with my Avalanche - UPDATE

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CPA

CPA

Elite Member
Now, before any of guys tell me to "go ask your mechanic", I won't be able to get the truck to him until next Thursday. So, in the meantime I thought I would see what you guys think the issues are.

1) AC fans blow erratically. This started yesterday. Either in Auto or Manual the fans turn on and off with no rhyme or reason.

2) Between 40 and 45mph the engine wavers. The rpms spike up, so it feels like the truck is rocking back and forth.

any ideas?

UPDATE: Interesting development with the engine wavering: when I'm at a higher rate of speed, say 65-70mph and then steer to the right (say on a highway), I get the engine wavering again. It doesn't happen on left bends.
 
Originally posted by: IHateMyJob2004
These two problems start at the same time?
Click to expand...

No. The engine wavering began weeks ago. The fans just started yesterday.
 
Vacuum leak? Will cause rough running and in many cars (don't know about yours) the blend door is vacuum actuated (a multiple position door in the ducting that determines if the air is going at your feet, your face, the windshield, or some combination).
 
My 05 Malibu will sometimes run the blower after the car is just turned off, the dealer said this is "afterblow", a normal condition. The wavering is a tough one, could be a throttle position sensor or a lot of other things..
 
My Silverado with the 5.3 does the wavering bit, I pretty sure its the intake gaskets. Mine has a crapload more miles, and I cant remember when it started.

Did you notice any weird cold start issues this past winter?
 
Originally posted by: Sluggo
My Silverado with the 5.3 does the wavering bit, I pretty sure its the intake gaskets. Mine has a crapload more miles, and I cant remember when it started.

Did you notice any weird cold start issues this past winter?
Click to expand...

No, but we live in Houston, so we don't get a lot of very cold mornings in the winter.
 
UPDATE: Interesting development with the engine wavering: when I'm at a higher rate of speed, say 65-70mph and then steer to the right (say on a highway), I get the engine wavering again. It doesn't happen on left bends.
 
Check your engine mounts. Use the mirror tool to examine the sides for any possible cracks. How is your tire wear? Even/Uneven? How long ago did you do the alignment? Wheel balancing?
 
Originally posted by: darom
Check your engine mounts. Use the mirror tool to examine the sides for any possible cracks. How is your tire wear? Even/Uneven? How long ago did you do the alignment? Wheel balancing?
Click to expand...

Tires are good. Had them balanced and aligned about 3 months ago.

Mirror tool? sorry, not much of a mechanic.
 
Have you washed the underhood area recently? Quarter car wash or even taken a hose to it?

You've got a strange mix of symptoms. I'm wondering if water has gotten into a connector or connectors somewhere. You may have a water leak that doesn't show itself in the passenger compartment. A leak down the inside of the front hinge pillar area. (This is just an example)

Water damage in a connector can be extremely difficult to diagnose.

This is just a guess. I wish I could give you something more concrete to look at. I would definitely be interested in what the resolution was when you get this fixed.
 
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