Engine/Transmission (1998.5 - 2002) Mileage and EGT issues

[hpyman123]

Replaced my VP-44 in May 05. Since then my mileage has dropped from 18. 5 to 16 in town and 20 from 22 on road. I've had EGT issues for a while. I have a TST PM3 box with an Edge EZ. With the box on 6 I can run EGT to 1450 very quickly at WOT. My boost is down from 35 to 30lbs. I have checked and tightened all the boots from the turbo to the air horn and found no problems. The mileage issue didn't happen until VP replacement. Egts have been high for a while but I don't just drive like a wildman so I can keep them acceptable until WOT. I bought the Vulcan LP kit but have yet to install it. I'm still running stock injectors. At 97K miles could they be my mileage issue? I'm concerned that if I go to different injectors the EGTs will be worse. My turbo is an HX35 hybrid with 14cm exhaust housing.

 

[nps]

Have you cleaned and/or replaced the IAT?

 

[hpyman123]

No I haven't done either. Could that be a source of the problem?

 

[nps]

Yeah, it could have an effect.



Also, you need to look at the intercooler boots for holes in addition to the clamps. The lower hose on the driver's side gets rubbed by the inner fender - this needs to be bent back. The upper hose on pass side gets rubbed by the AC pressure switch - it also needs to be bent gently back and away.



The best way to test for boost leaks is to pressurize the intake. Make an end plug out of a 4" PVC cap or a 4" circle of plywood/particleboard and put an old valve stem in the middle. Pressurize with less than 40psi and listen for leaks. Many times you will find an intake manifold bolt loose, or the gasket around the grid heater leaking, etc.

 

[hpyman123]

I checked the boots by pressurizing the intake as well and found no leaks. The intake is not leaking . I replaced the gaskets with new when I did the injector pump. Torqued to 18 ft/lbs then checked them again a week or so later after the truck had been driven for a while. Anything else? I'm about to pull out what little hair I have left on my head.