so today i ordered a live data capable scanner and did a vac test. initially on cold start (when its usually running like **** for the first 30 secs to 2 mins(rough idle and heavy miss with throttle)) it is pulling like 10, and when this condition is no longer present, the vac gauge read more along the lines of 18-20. when throttle was applied by hand the gauge dropped at the initial throttle and then built beyond 20. i cant pull the hood and drive around with the vac line extended to the cab and monitor the gauge in the case where it starts acting up at operating temp, so i eagerly await the arrival of this new scan tool. i will update with more info after i get a chance to look at some of the data.

 

these are the features that are compatible with the scan tool on my blazer:

Live Data:

• Fuel system status
• Calculated LOAD Value
• Engine Coolant Temperature
• Short Term Fuel Trim - Bank 1 / Bank 3
• Long Term Fuel Trim - Bank 1 / Bank 3
• Short Term Fuel Trim - Bank 2 / Bank 4
• Long Term Fuel Trim - Bank 2 / Bank 4
• Intake Manifold Absolute Pressure
• Engine RPM
• Vehicle Speed Sensor
• Ignition Timing Advance for #1 Cylinder
• Intake Air Temperature
• Air Flow Rate from Mass Air Flow Sensor
• Absolute Throttle Position
• Bank 1 - Sensor 1
• Bank 1 - Sensor 2
• Bank 2 - Sensor 1 / Bank 3 - Sensor 1

 

The truck will never run properly with a significant vacuum leak. To help confirm record the four fuel trim numbers at idle and again at 2500 rpms. Be mindful of sign (+/-).

so it runs good when cold but crappy after it warms up? If so watch on live data to see when the fuel system transitions from open to closed loop operation and see if that’s when the truck starts to run crappy.


George