Join Date: Jun 2010
Location: Middleville, MI
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Powerloss and MPG
Recently I have seemed to have developed a loss of power towing and my fuel mileage has decreased. While the truck seems to run smooth, no smoke of any color, and when not towing seems okay.
I have a auto meter boost and egt gauges, I don't seem to be making the boost I once was. I don't drive the truck often, maybe once a week or two weeks. Mostly used to tow my trailer and early bronco or to haul something. Problem seemed to really develop over a two day trip.
I first noticed a loss of boost psi in my gauge. 20 psi wasn't uncommon if I was into it hard. But now it seems 10 is a struggle and 5 is typically the max. Granted it could be the gauge itself. But I do feel a loss of power so I doubt it.
I have gone over it and found no leaks where I could be loosing boost, checked the impeller and looks good along with play in the impeller. I have about 500 miles since my last change with rotella. New fuel filter and air filter and cleaned the fuel manifold screen. I have a mbrp downpipe and straight pipe 4". New mechanical fuel pump, new cam sensor. Last year it got a new ebv pressure sensor and the tube thoroughly cleaned, Fuel Injection Control Pressure Sensor.
I pass the contribution test, and the buzz test keeps flagging a p1298 idm fault. But everything I have read states I should have a no start condition with this code, I don't it start fine.
Some quick numbers I grabbed with the scanner
ebv psi seems to read about 15 psi about 50 mph
ICP voltage about 1 cruising and 3.0 WOT
Inj control pressure approx 2500 at wot
Map at idle 14 psi and approx 22 wot
I tried unplugging the map and made no difference. I also have wired the ebv valve open and made no change.
@ idle 70 psi with a 3 psi swing or pulse in the needle. With key off drops to 50 psi and gradually loses pressure very slowly. At WOT seemed to center around 50 psi with a violent pulse in the needle. This was before I replaced the mech pump.
When towing I typically see 14-16 mpg and I am now getting 9-10 at best.
I also seem to be running higher egts then normal. Seems when towing it pretty much stays at 1200 while attempting to maintain any highway speed. It doesn't seem to push past 1300 no matter how hard I push it.
I think some of the power loss is the stock Torque converter at 256K miles. My trans shifts fine, but I am pretty sure the converter is tired and robbing some power. But I wouldn't think I would lose boost over it.
I don't have access to a scanner today. I can't say for sure as I don't drive the truck often and rarely ever through the winter, but if I had to say I think the idle is ever so slightly rougher. I honestly cant tell but it just 'feels" off from what I thought it had been and almost to me sounds just a hair different at idle as well. I can't say for sure but its just this slight observation. It might not be at all different then its ever been but just a feeling
1997 F250 Crew Cab Short Box
7.3L E40D 4x4 SRW
3" MBRP Downpipe 4" Pipe
Boost and Pyro Gauges