Dead throttle off idle

[fast03]

Any ideas on what might be the cause of this problem. Truck seems to run great, but off idle throttle response has gone to crap. If I mat it from a stop I do not get the normal puff of smoke then hard acceleration. It feels like a slug until the boost builds to like 10psi then it starts pulling and eventually gets to about 28psi of boost and pulls real hard. Just seems to have lost the bottom. Tried a few different tunes and they all seem to do the same thing.

 

[Dirtymaxx03]

any logs?

 

[fast03]

I logged it a couple months back with a 60hp predator tune. I do not normally run this tune, but I know its pretty peppy off the lineI cannot upload it now, but will try tonight

 

[Dirtymaxx03]

why not log it on a tune you use often?

 

[IOWA LLY]

Maf.

 

[fast03]

why not log it on a tune you use often?

yeah will do that later tonight after work, with the tow tune I usually run. I have not been driving the truck too much recently so I have been a little slow to get to a fix.

 

[fast03]

Maf.

Should I replace it or clean it, to try for a quick fix. I will still log it tonight and post it up tho. Thanks

 

[Dirtymaxx03]

just clean it. but i would think a dirty maf would cause exessive smoke. then you may need to try replacing it.

 

[fast03]

just clean it. but i would think a dirty maf would cause exessive smoke. then you may need to try replacing it.

That would make sense, but who knows. I will log it, clean it, log it again.

 

[JustinD]

Mine has this problem too, only in 4 low though??? at the dragway it launches awesome, go to the pulls won't spool til its too late??

 

[fast03]

here is log. yep not that I want to blow smoke, but this tune usually would leave a bit of smoke on off idle wide open runs and now not getting that. tho it seems to pull hard once boost is up over 15-20 range

 

[fast03]

bump

 

[Bustedknuckles]

Any ideas on what might be the cause of this problem. Truck seems to run great, but off idle throttle response has gone to crap. If I mat it from a stop I do not get the normal puff of smoke then hard acceleration. It feels like a slug until the boost builds to like 10psi then it starts pulling and eventually gets to about 28psi of boost and pulls real hard. Just seems to have lost the bottom. Tried a few different tunes and they all seem to do the same thing.

Mine did the same thing, I sent logs to Rob and its awesome again. Idk what he did or what was wrong though.

 

[fast03]

So still having this issue. Better decription is no throttle response until 10-12 psi boost. I am getting no smoke at all( not that I want it). Truck pulls good with my toyhauler behind it, I guess because it is building boost then with a load. Anytime I thottle up from stop or cruise its just a slug until boost rises. I ramped up rail pressure to 26k at idle, I do not get a rail pressure drop when logging. Mileage seems ok. It is like it just won't fuel until boost is up. Does not matter the tune. Was thinking to try maf sensor, but I do not have black smoke, which I thought was a typical symptom. I get no codes. I only have egr codes turned off in the tune I am running, so it seems I would get a maf code if it was a probelm. Thanks in advance Steve

 

[McRat]

MAF is reading too low.

This is based on your datalog. Whether that is problem or not, can't say. It certainly isn't showing enough air going in, nor enough fuel being injected.

This can be fixed through tuning, the MAF is stupid expensive for LB7's. Might try cleaning it with carb or brake cleaner first.

 

[fast03]

MAF is reading too low.

This is based on your datalog. Whether that is problem or not, can't say. It certainly isn't showing enough air going in, nor enough fuel being injected.

This can be fixed through tuning, the MAF is stupid expensive for LB7's. Might try cleaning it with carb or brake cleaner first.

Thanks Pat. I cleaned it already with no improvement. Can the MAF actually limit injection quantity that much? I can try to rescale the maf, but not real sure what I would need to change the table to