I'm doing some troubleshooting and need to know how other trucks act...

If you are cruising down the road at highway speed and you let completely off the throttle, what does your rail pressure do? Drop, stay the same, go up?

Also, when you get back into the throttle what does it do? Go back up or drop first then go up?

Thanks for any help, I'm trying to determine if I have a problem or not.

 

cruising at 70, pressure steady at 20k
let off and it immediately drops

get back in the throttle and it immediately shoots up to 23k and if I'm wot it will build to 24k sometimes 25k. 4.10 BA431 tune (similar to 4.4) Doesn't drop

 

When I get out of the pedal quickly it goes up 1.5-3K from what I was running at. Then immeadiately drops ~10K until I get back into it again. Doesn't matter if I get in it hard or ease back up to a cruising speed it will always climb until it is not demanding any more fuel.


Hope this helps

 

Ok, then I definately have an issue.

Cruising 70 or so, it is around 13-14k. If I let off the throttle, it will raise to 15k and stay there until I slow to less than 10 mph or until I get back into the throttle, in which case it will drop to somewhere around 3k (sometimes 2k) and then come back up to 13 or so. It causes a full second delay before the power is back or starts to come back.

Anyone know why? Sticky FCA?

 

Any poss. of wrong voltage or computer issues????



How does this compare to your previous problem??



Sounds like a sticky FCA again......................................

 

Previous issue was that the rail pressure was 14.5k max. Turned out the ECM needed a vehicle speed signal or it defuels. So I got that connected, and max rail pressure was then around 18.5k.

Bob W. sent me a recovery file and I reflashed the ECM to clean up any possible issues created when the dealer put my VIN # in for me. Then I loaded a different smarty software aftermarket turbo/stock injectors mod TM onto the ECM. It does run alittle better, max rail pressure is around 20k.

However the issue with the pressure drifting up after getting off the pedal, and then dropping first when I get back into the throttle has been there from day 1.

When I disconnect the rail pressure connector, rail pressure goes straight to 26,500 psi...

 

It sounds like your cruising pressure is right (10-13k). 20k at 70 sounds high to me and I even run a pressure box. But i think you definitely have a problem. Mine drops immediately.

 

FCA is roached

 

I guess that's next on the list then...

 

when i gun fuel pedal half way and then let off quickly it seems as though fuel/rpm stay for like 20 seconds. i have to use brake hard to slow truck down and rpms still stay high. just sometimes.is fca sticky? because i replaced it this past summer.

 

Jlibert, is this 4.10 a custom tow tune? Or is it just one of the older tunes? Just curious cuz you say its similar to the 4.4 which was a beta tow tune. Sorry im not trying to hi jack this thread.