Cold Morning Starts

[Garrett Street]

I have a 99 Silverado 5.3 with 200,000 miles on it. At the beginning of summer the SES light came on and I had it checked. The code came back "Misfire on random cylinders". Now that it's starting to get cold out in the mornings my truck has a hard time running. It will shutter and almost die if it's cold out but when it warms up it runs perfectly. This only happens when the truck is completely cold, so in the mornings and occasionally when I get out of work. I'm thinking it could be a vacuum leak of some kind but I have no idea really. Any advice?

[RockySierra]

You've got a number of things that could be going on here. When did you last change plugs and wires and what did you use? Have you cleaned your MAF sensor lately? Have you cleaned your throttle body lately? Have you done a seafoam treatment or had a motor vac done lately? All those could help. YOu may end up just throwing money at the truck unless you take it into a shop to have it diagnosed. Don't have to take it into a dealer, a reputable shop with the right diagnostic tools should be able to do it. But first off, start with the basics, Fuel, Air, and Spark.

[Garrett Street]

How do you clean the MAF sensor and throttle body? I changed the plugs and wires about a year ago so they should be good. Idk what to do about this. It's really annoying.

[jblakeney]

I have a 99 Silverado 5.3 with 200,000 miles on it. At the beginning of summer the SES light came on and I had it checked. The code came back "Misfire on random cylinders". Now that it's starting to get cold out in the mornings my truck has a hard time running. It will shutter and almost die if it's cold out but when it warms up it runs perfectly. This only happens when the truck is completely cold, so in the mornings and occasionally when I get out of work. I'm thinking it could be a vacuum leak of some kind but I have no idea really. Any advice?

 

Yea, tell us the DTC's................ PXXXX

 

Jbo

[Garrett Street]

DTC's? What does that mean?

[jblakeney]

DTC's? What does that mean?

 

Diagnostic Trouble Codes.

 

Jbo

[txab]

DTC's? What does that mean?

 

Diagnostic Trouble Codes.

 

Jbo

 

Yep without checking for those your wasting time.....

[8.1HD/ALLISON]

Intake manifold gaskets are very common on those with the symptoms you are describing. Check codes.