96 Yukon stumbles or just about shuts off when first acclerating

[scottsdale816]

I have a 96 Yukon with 5.7 and have started having a problem with it after it sits for awhile,few hours or overnight. When I first start it it runs fine but when I start to accelerate it stumbles or has very bad hesitation like it is going to shut off. But after that first time it runs fine with no problems again until it sits awhile. It acts how an older carburetor model would act if it was not warmed up enough before taking off. Any help would be appreciated. I have not checked fuel pressure because it is running great otherwise. Fuel filter has been changed. Injectors were changed 3 years ago, and throttle position sensor replaced about 8 months ago. No check engine light on.

 

[lesterl]

Clean the Mass Airflow Sensor, Check fuel pressure.

 

[scottsdale816]

Ok I will try that, I also noticed today that if you start it after it has been sitting awhile you can race the engine in park and it does not hesitate at all but if you put in gear it will stumble when you try and take off.

 

[lesterl]

Might also check the EGR flow..... It could be leaking a little bit.....

 

[jmarkham1249]

Could be dirty throttle body mine did that and clean it no more problems

 

[laredo1307]

Had the same issue, especially in the mornings. Turns out there was corrosion under my distributor cap. I had done a tune-up about 6 months prior and used an aftermarket cap that had brass points in it. This ended fouling out my plugs and destroying my new catalytic converters. Needless to say when I fixed everything I went back with AC Delco parts and have not had any problems.