Engine/Transmission (1998.5 - 2002) Please help, poor mileage & performance

[DHoeck]

I am a new owner of 2001 3/4 auto. It has a 105,000 miles and was babied by previous owner with no pulling/hauling, etc. Now I have it and the mileage seems poor (14mpg). Also, the performance seems off. It seems like a "dawg" when accelerating. My only reference is a 94 chevy with a 350 in it. Lift pump pressure is 5-10. truck looks excellent, the auto-trans and rear diff looked excellent without evidence of wear. Is this mileage in the ball park and without going crazy what could I do to inprove its performance, etc. I plan on using it as a truck pulling my 5th wheel. Thanks for any suggestions.

Dwight in Kellogg Idaho

 

[nps]

Welcome to the TDR.



Several things to check. Regarding mileage, the IAT sensor has been known to get dirty or fail, and cause poor mileage. Remove it and clean.



Regarding power, two things to check are the MAP sensor and boost hoses. The MAP sensor tells the ECM how much boost there is, and then adds fuel. If it is slow to respond you may not be getting fuel to the engine.



The boost hoses tend to rub and get holes, especially the lower intercooler hose on the drivers side. If your boost is leaking you won't get enough fuel to the engine.



As far as normal mileage, it varies depending on driving style and road conditions. Unless you are in stop and go city driving, I think 14 is a bit low. I get 14 on the highway pulling my 10K# trailer.

 

[KLockliear]

Lift pump pressure 5-10? How much at idle and how much at WOT? 5 is too low at any time. You should see minium 10psi at idle, preferrably higher. Up to 14psi is stock. No less than 6psi WOT.

 

[DHoeck]

Thank you!. I,m 10 psi at idle and 4-5 at wot. I have lost all pressure a couple of times while WOT. It comes back after about 30 seconds. I was told I should be getting 18-20 mpg,I live by and do most of my driving on an interstate.

 

[RCook]

I'd say 14 is way low, unless you have a heavy foot much of the time. I get 16 on city streets, 20+ highway.



I'd check those sensors, make sure all 7(?) of the boost hose connections are tight, make sure there's a clean air filter, replace that lift pump, and adjust the valves unless it's been done carefully and recently.



You might also try a few fairly generous doses of Stanadyne Performance Formula fuel additive. It's supposed to lube the injector pump and keep injectors clean, among other things. I've been using it for years now, and I find my engine runs quieter, smoother, less smoky, and actually gets about 1mpg better when towing than when I don't add it at a fillup. 103K miles, mostly towing, and it runs like a top.



If you're towing in the mountains as I do, you might really appreciate the BHAF air filter. I added an Edge EZ and BHAF, and mine pulls just great, with no worries. Get it running well first before adding the Edge.

 

[southpaw]

I have three ctd's 2 were bought used and were babied ran fine but terible milage I was advised to hook up to some substantial weight and go for a long ride 2-3 hundred miles and break it in . The advise was good. only after you check out the suggestions made in the above posts.

 

[DHoeck]

Thanks for the advice. I have put in egt,fuel press,boost gauges. All fluids and air changed. How much would you recomend I pull and should I put my edge box on before or after I try working the engine? I will change the iat sensor first.

 

[TWhetten]

You might check to make sure your lift pump is working. My truck has 15psi at idle and never goes below 11-12psi at wot. I have the vulcan big line kit, and my lift pump has been relocated, but even before that it was never that low. If your lift pump is out it can cause your injection pump to fail.

 

[barbwire]

Another thing to consider is winter blend fuel. It has less energy than #2, for antigel purposes. It will knock your mileage down.