Defueling at WOT

[Diesel Freak]

I thought my BOMBs had cured this, but I had adjusted my driving style to accomodate the problem. My engine has less power at WOT than at 3/4 throttle. I know this for a couple of reasons

1. at wot the clutch will not slip in 5th or 6th gear

2. at 3/4 throttle the clutch can not hold

Last night I think my boost gage went TU... . pressure rises fast, but stops at 28 psi when it usualy pegs out at 30 power is the same in both cases. I can get to 30 psi, but I have to roll into the fuel slowly. Also because of the high humidity lastnight I hit 1150F on the pyro. This is why I started paying more attention to my driving style and what happens to my instrumentation when I do certain things (a little highway troubleshooting) I am at a loss at the moment. I think I am going to remove my boost elbow and see what happens. I may get a new MAP sensor and see what that does. Are there any other suggestions out there?

-Cliff

 

[Diesel Freak]

I ordered a new 2-50 psi Boost Gage from ISSPRO to replace my autometer 30"Hg-30 psi that may be TU... hopefully this wil help me narow down my problem.



I am still open to suggestions.

 

[Bigsaint]

Cliff, with my limited experience, the only thing that comes to mind is fuel pressure. If the FP is okay, I think I'd try a new map sensor as well, but maybe someone with more experience can chime in here.

 

[DAWG-1]

Find a SEAT COVER!

Then you won't notice . Sam

 

[work2muchplay2little]

Diesel Freak, I'd agree with BigSaint regarding the fuel pressure. Don't know what lift pump is being used on late model trucks, but many drop to 0 psi at WOT. I just replaced mine today as sort of a preventive maintenance thing. Another thing, I don't know if you're using a Psychotty air intake, but I had a problem where the plastic Psychotty duct cracked allowing the K&N to slide further into the duct and at WOT would suck itself against the plastic causing a major drop in performance. Fixed for now with several tie wraps. But if it were me, I'd be buying/borrowing a fuel pressure gauge and checking that avenue first.



Good luck !!

 

[Diesel Freak]

I do not thnk it is fuel pressure, the problem has been there since the truck was new. I will check it anyway. I priced a MAP sensor at the dealer $145 I got the part number and I am going elsewhere

Boost Sensor #5017791AA



I am also going to see if my Boost Module has gone TU again. Darn solid state components should not behave like this... . they either work or they don't! Not sometimes!



As for the seat cover "covering up the engine problem" hehe I doubt it even an Anna Kournikova seatcover would not would make me feel better once I get diesel on the brain.

-Cliff

 

[Diesel Freak]

My truck is as moody as my ex-fiance. I guess it found out that I bought it a new boost gage. it is running better, but the gage is still TU. and I still have a slight cutback at WOT.

 

[Bigsaint]

I still say FP, especially if it's sporadic, they seem to do that when they are first starting to go. Should be interesting to see what your psi's are at WOT. I wouldn't put it off too long, in case it is the Carter pump, it may take out the VP44 as well if left unattended. Keep us posted.

 

[ynot]

Not sure is this is applicable or not, but on my last dyno run, I saw peak HP drops on every re-run. With all of the posts on the IAT sensor, I'm gonna try taking it out of the manifold, plugging the hole, and running the IAT in ambient. At least won't get an inlet temp de-fuel that way. This will probably go against the reason for the original IAT post, but mileage isn't as much of a concern to me as HP. Map sensors or plugged exhaust/ air cleaners are the main cause for defueling that I've seen. Good luck... T

 

[Bigsaint]

but mileage isn't as much of a concern to me as HP

Don't know you but I like you already



Scott W.

 

[Marco]

I think it's the first time that I see someone notice the defueling @ WOT.



I'm surprised! The defuelling at WOT comes from the ECM so anyone should notice it.

It's due to the throttle VS. boost curve in the ECM. Then higher the RPM then more noticeable it becomes.



Diesel Freak, since you CAN get the power at 3/4 throttle, I think there's nothing wrong with your fuel pressure.

Marco

 

[John]

Originally posted by Diesel Freak

I doubt it, even an Anna Kournikova seatcover would not would make me feel better once I get diesel on the brain.

Oh yes she would!!!!