99 Tahoe OBS 4wd, 5.7Ltr, 98k miles.
When the vehicle is warmed up and only when warmed up and I put it into gear whether going into reverse or Drive the truck will stumble to point where it feels as though the engine will die. I have no major mods and this has been occuring for the last 2 yrs. I have done all regular maintenance and tune-ups. Latest full tune up is 6 months old with no improvement.
I do not have any vaccum leaks and all electrical looks good, no corrosion or melted connectors.
When the truck is put into gear the RPM's stumble to around 250rpm to 300rpm. Then after giving the truck gas to accelerate everything is fine. The symptom seems to me like something is not compensating for the additional load when put into gear. The truck will do it the same whether accessories are on or off.
Intake gaskets are new since installing the Delphi MPFI kit. Throttle body completely cleaned. IAC Cleaned as well. Upper and lower intake were completely cleaned inside and out at a local engine shop.
I have replaced the the MAF with the updated Delphi unit
New Delphi Map Sensor.
New Delphi coolant Temp sensor
Delphi TPS
No CEL
The truck runs great. Performance is good, and MPG's are within normal range.
Im left wondering if O2 sensors can cause this or if a IAC valve could or maybe even the EGR.
These are the only electrical/emissions related parts I have not replaced since owning the truck for the last 6 years.
The stumble is bad but it only happens when the vehicle is warmed up and first put into gear. This is why this is so werid.
Any ideas would be great.
When the vehicle is warmed up and only when warmed up and I put it into gear whether going into reverse or Drive the truck will stumble to point where it feels as though the engine will die. I have no major mods and this has been occuring for the last 2 yrs. I have done all regular maintenance and tune-ups. Latest full tune up is 6 months old with no improvement.
I do not have any vaccum leaks and all electrical looks good, no corrosion or melted connectors.
When the truck is put into gear the RPM's stumble to around 250rpm to 300rpm. Then after giving the truck gas to accelerate everything is fine. The symptom seems to me like something is not compensating for the additional load when put into gear. The truck will do it the same whether accessories are on or off.
Intake gaskets are new since installing the Delphi MPFI kit. Throttle body completely cleaned. IAC Cleaned as well. Upper and lower intake were completely cleaned inside and out at a local engine shop.
I have replaced the the MAF with the updated Delphi unit
New Delphi Map Sensor.
New Delphi coolant Temp sensor
Delphi TPS
No CEL
The truck runs great. Performance is good, and MPG's are within normal range.
Im left wondering if O2 sensors can cause this or if a IAC valve could or maybe even the EGR.
These are the only electrical/emissions related parts I have not replaced since owning the truck for the last 6 years.
The stumble is bad but it only happens when the vehicle is warmed up and first put into gear. This is why this is so werid.
Any ideas would be great.
