Hesitation on immediate full throttle

[bluescapegoat]

This has always been something that my 05 has done since day one. I think this would apply to both manual and auto but I would expect is much more obvious with a manual. I also suspect this is a PCM issue only specific to the 05-06, and maybe as early as 03.

When going from low or no throttle to full throttle very quickly, ie 2 to 3 shift at 3500 rpm, the engine will not exactly bog, but hold rev for about 1 second before accelerating again.

It was simply a curiosity when my Jeep was in stock form but now that it's supercharged it's going lean while blowing 6.5 psi down it's throat so I'm trying to figure out the cause. I think it's stemming from the tip in timing retard.

I know I'm not the only one, an internet search brings up several threads from people upset about this with their new TJs in 05/06/07. What I want to know with this thread, is who else experiences this now, and the year/trans information about your vehicle, and any fixes you may have tried or general observations

 

[LONGJP2]

My 06 auto does it. Pretty much every time I rev the engine (in Park/Neutral). I don't notice it too much while driving since I have no need to floor it from a dead stop.

 

[MutantNinjaTJ]

I don't see anything like that out of my 05 manual.

 

[Goatman]

06 Rubi 6 speed. Nothing. Have very good acceleration.

 

[mots]

This has always been something that my 05 has done since day one. I think this would apply to both manual and auto but I would expect is much more obvious with a manual. I also suspect this is a PCM issue only specific to the 05-06, and maybe as early as 03.

When going from low or no throttle to full throttle very quickly, ie 2 to 3 shift at 3500 rpm, the engine will not exactly bog, but hold rev for about 1 second before accelerating again.

It was simply a curiosity when my Jeep was in stock form but now that it's supercharged it's going lean while blowing 6.5 psi down it's throat so I'm trying to figure out the cause. I think it's stemming from the tip in timing retard.

I know I'm not the only one, an internet search brings up several threads from people upset about this with their new TJs in 05/06/07. What I want to know with this thread, is who else experiences this now, and the year/trans information about your vehicle, and any fixes you may have tried or general observations

Perhaps someone familiar with forced induction tuning on manuals will chime in, but I read somewhere that the manuals are harder to tune in this regard, i.e. fighting A/F ratio during boost recovery after shift points etc.

 

[mots]

Perhaps someone familiar with forced induction tuning on manuals will chime in, but I read somewhere that the manuals are harder to tune in this regard, i.e. fighting A/F ratio during boost recovery after shift points etc.

P.S. 2005 4.0 6-speed here. Great acceleration after 3 new cats (2 pre-cats partially clogged) and new Bosch fuel pump made it even better. How many miles? Is your exhaust original? Some limiting factor like this could also be holding you back.

 

[bluescapegoat]

P.S. 2005 4.0 6-speed here. Great acceleration after 3 new cats (2 pre-cats partially clogged) and new Bosch fuel pump made it even better. How many miles? Is your exhaust original? Some limiting factor like this could also be holding you back.

Was the same with all three cats. Now it's entirely catless, running open loop so it's not fighting a/f adjustments, and still does it exactly the same as stock form closed loop. It's had 4 different exhaust configurations on it at this point. 80k miles now, got it with somewhere around 30k. Just put a brand new fuel pump in it after I broke the last one dropping the tank.

The tuning allows for up to 8 degrees of timing retard on tip in and there are adjustable option for bobble management. I have a couple copies of tunes from aftermarket boost kit manufacturers and they appear to disable the tip in retard.

I might add, it doesn't do it every time. Not at all. About once out of every 50 times.

 

[Chris]

You've remove all three cats, but have you disabled the post cat O2 sensors?

 

[mots]

Was the same with all three cats. Now it's entirely catless, running open loop so it's not fighting a/f adjustments, and still does it exactly the same as stock form closed loop. It's had 4 different exhaust configurations on it at this point. 80k miles now, got it with somewhere around 30k. Just put a brand new fuel pump in it after I broke the last one dropping the tank.

The tuning allows for up to 8 degrees of timing retard on tip in and there are adjustable option for bobble management. I have a couple copies of tunes from aftermarket boost kit manufacturers and they appear to disable the tip in retard.

I might add, it doesn't do it every time. Not at all. About once out of every 50 times.

Sounds like you have an interesting custom setup. If you have a post\page the describes the details, I would love to read more about it. If there is something quirky with the PCM logic that some don't like, and that you have noticed, then it is very likely going to be amplified and accentuated after tuning (if it isn't something known that tuners can "tune out"). If it only happens 1 in 50 times, and happened before the tune, and doesn't ever correspond with detonation, then it is more than likely just some quirky part of the PCM logic that still there and part of the tune.

"Tip in retard" would definitely be one of those things that would be accentuated and more annoying after a tune, since the idea is to reduce torque during shifts to be easier on the transmission (by running less timing advance). Reducing or removing this retard can yield performance benefits, but at the cost of transmission longevity.

That said, the part you noted in the original post about going lean after the 2-3 shift under full load at 3500 RPM would definitely concern me if reproducible. Do you have a wideband sensor you are logging with in real-time as you wring out 3rd gear? It wasn't clear to me if you were doing logging and linking the lean condition with the the "pause" you felt in acceleration or not. Sometimes logging is odd with AFR on some platforms and you aren't really seeing what you think you are seeing between shifts.

 

[bluescapegoat]

You've remove all three cats, but have you disabled the post cat O2 sensors?

Yeah, rears are disabled, removed, plugged, and associated DTCs are disabled.
Front O2s aren't technically disabled, but the codes are disabled on them and the PCM is running open loop 100% of the time.

Do you have a wideband sensor you are logging with in real-time as you wring out 3rd gear? It wasn't clear to me if you were doing logging and linking the lean condition with the the "pause" you felt in acceleration or not. Sometimes logging is odd with AFR on some platforms and you aren't really seeing what you think you are seeing between shifts.

I have a wide band o2 welded in after the merge in the exhaust and a vac/boost gauge directly off the manifold.
I've done some logging but haven't caught it yet. I'm observing it on the gauge when it occurs in daily driving.

 

[astjp2]

Throttle position sensor problems and shift cable being out of adjustment can cause hang shifts

 

[bluescapegoat]

Throttle position sensor problems and shift cable being out of adjustment can cause hang shifts

TPS seems fine, but again, haven't logged it when it acts up, just monitored it while driving and tested it when I was having trouble with the closed loop/open loops transition a while ago. I can't truly rule that one out. Maybe I should swap it and see what happens. That would be a very very intermittent short that hasn't changed in condition in several years but I could definitely see where that could be sending air in and not giving it fuel and causing the condition I'm seeing.

And... shift cable? Maybe I wasn't clear before, it's a 6 speed. It definitely feels likes it's an act of the PCM.

 

[astjp2]

Sorry, I read so many posts today that I was thinking you may have an auto. The tps can be measured with a descent multimeter. Check for voltage out, don’t trust the pcm if it is suspect.