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1999 GMC/Chevy 2500 Cold Hesitation

Sent to Car Experts January 24 08:54 PM

I have a 1999 GMC 2500 pickup, 5.7 Vortec with automatic trans and four wheel drive. I live in Tucson, and this time of year it will go down to 35 or 40 degrees aovernight.

Truck always starts easily. After the truck is started for the first time in the morning, I will experience a hesitation or stumble when accelerating away for the first time after backing out of the drive. This could last 2-10 seconds. Usually once this occurrs, it will not happen again until the next morning. There have been a couple of occurrences when this has happened later in the day when the truck has sat for 30 minutes or more, but this is less frequent. The truck will accelerate fine under full throttle once it has fully warmed up. Check engine light does not light during or after episodes? What would you suggest to try first in troubleshooting this problem?

Bill Cooper

Optional Information:
1999 GMC K2500 350 Vortec

Customer (name blocked for privacy)
Status:  Closed   Value: $8
Answer
January 24 9:32 PM (37 minutes and 49 seconds later)
         
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Michael -- Auto Service Technician -- 99% Positive Feedback on 598 Car Accepts
21yrs.Foreign and domestic driveability diagnosis and repair/ ASE Cert./Fuel Injection Specialist.
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January 24 9:42 PM (10 minutes and 5 seconds later)
         
I've seen a number of posts pointing to the MAP sensor as a possible cause. Do these fail intermittent, and how do you confirm a good or bad unit?
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January 24 10:05 PM (22 minutes and 51 seconds later)
         
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Michael -- Auto Service Technician -- 99% Positive Feedback on 598 Car Accepts
21yrs.Foreign and domestic driveability diagnosis and repair/ ASE Cert./Fuel Injection Specialist.
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January 24 10:08 PM (3 minutes and 5 seconds later)
         
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Michael -- Auto Service Technician -- 99% Positive Feedback on 598 Car Accepts
21yrs.Foreign and domestic driveability diagnosis and repair/ ASE Cert./Fuel Injection Specialist.
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January 24 10:10 PM (2 minutes and 36 seconds later)
         
Michael,

This relates to my first question about the hesitation and whether a faulty MAP sensor could be the cause.

I guess what I was expecting was a couple of suggestions to try in a sequence that you would believe to be logical.

I cleaned the plunger on the IAC about a year ago and that cured a hunting idle situation because the tip was carboned up and would not seat properly.

Sorry...
Customer (name blocked for privacy)
Reply
January 24 10:14 PM (3 minutes and 46 seconds later)
         
Good answer. So, probably best to just wait for a hard failure...
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January 24 10:19 PM (5 minutes and 22 seconds later)
         
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Michael -- Auto Service Technician -- 99% Positive Feedback on 598 Car Accepts
21yrs.Foreign and domestic driveability diagnosis and repair/ ASE Cert./Fuel Injection Specialist.
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January 25 7:13 AM (8 hours and 53 minutes and 46 seconds later)
         
OK. So I have one suggestion for a fuel system cleaning. I guess I had a higher expectation as I mentioned.

Sorry for the trouble.

Carnutz
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January 25 7:42 AM (29 minutes and 4 seconds later)
         
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Michael -- Auto Service Technician -- 99% Positive Feedback on 598 Car Accepts
21yrs.Foreign and domestic driveability diagnosis and repair/ ASE Cert./Fuel Injection Specialist.
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