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2000 Sierra 4.8l Cold Hesitation

pkradam

By pkradam
in Ask A GM Technician

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pkradam Enthusiast

pkradam

Posted
Posted

Hi There,

 

I have a 2000 sierra 4.8l with 198000 kms. When started cold I notice the throttle is very unresponsive. It will take up to a minute appx before any acceleration will occur. The truck seems to be struggling with towing my 4500lb trailer as well. The tune up condition is ok. fuel press at idle/no load was within spec. Exhaust pressure before cat indicated no cat clogging as well.

 

Any previous experience anyone can share with this problem would be greatly appreciated!! Thanks in advance!

txab Senior Enthusiast

txab

Posted
Posted

You've towed this trailer with this truck before with no problem? Or did you just get this truck?

pkradam Enthusiast

pkradam

Posted
  • Author
Posted

Had the truck since new. Just got the camper this year. The truck really struggles with slight inclines and shifts quite harshly when I have to really lay into it. I don't know if the two problems are related however everything seems fine otherwise.

txab Senior Enthusiast

txab

Posted
Posted

Check your glove box for the RPO codes for your rear end ratio or do you know it already?

 

Here are a few:

 

GT4 Rear Axle: 3.73 Ratio

GT5 Rear Axle: 4.10 Ratio

GU4 Rear Axle: 3.08 Ratio

GU6 Rear Axle: 3.42 Ratio

 

Also when you say "It will take up to a minute appx before any acceleration will occur", do you mean you press the pedal and engine doesn't change RPM at all?

pkradam Enthusiast

pkradam

Posted
  • Author
Posted

I dont remember my axel ratio, but my tow capacity is 6400lbs. I subtracted 20% to allow for age and varailables in weights when picking my camper. My campers max loaded is actually 4500 lbs. I'm likely pulling it at closer to 4000lbs with water on as it's dry weight is about 3600lbs. I had the dealer also install an additional transmission cooler to be on the safer side. I have friends pulling similar campers with comparable trucks without much difficulty.

 

EDIT it's GT5 4.10

pkradam Enthusiast

pkradam

Posted
  • Author
Posted

What I mean by acceleration to occur is I push the throttle and the engine rpms do not respond hardly at all. After a short period of time 15 - 30 seconds its almost like the truck goes " Oh, we are trying to go somewhere! OK let's go" and my acceleration is normal.

pkradam Enthusiast

pkradam

Posted
  • Author
Posted

I put in a new mass air flow sensor and all the problems have dissappeared. I had forgotten how well this truck drove even under normal conditions lol.

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