Dead spot at 3200rpm

[swc69]

Hey All,

I have a dead spot in the power band at about 3200rpm. When I'm accellerating, when the tach hits 3200 the car bogs for a few seconds, and then takes off again.

Its really annoying. Does everyone have this problem?

Steve C.
2003 300A

[halucin8]

I noticed this in my MM before the GF wrecked it. I thought maybe it was a torque convertor thing going on.

It is very noticeable. On my car it seems to only happen during normal/moderate acceleration. Under hard accel, nothing.

[TripleTransAm]

There's been some discussion about this previously. It's either a 2-3 upshift with no TCC engaged (ie. the torque converter soaks up the upshift jolt) or a somewhat premature (thanks to the factory) TCC application during acceleration. Once I get my OBD-II scanner s/w I'll confirm...

[RF Overlord]

The Bunny Lady doesn't let me drive the Blackbird very often, but I did manage to weasel it out of her yesterday by promising to go to the dump... *sigh*

Anyway, I did not at that time, nor have I ever noticed a lag or bog at any RPM during any level of acceleration...

And to answer your other post, swc, I don't have any weird shifting issues, either...

[CRUZTAKER]

Mine regularly did this before the chip install. It's all in the programming.
Deja Vu thread...

[Murader03]

Hey All,

I have a dead spot in the power band at about 3200rpm. When I'm accellerating, when the tach hits 3200 the car bogs for a few seconds, and then takes off again.

Its really annoying. Does everyone have this problem?

Steve C.
2003 300A
Yea! I had it also, until I installed DR's Stage-1. Took care of the shift problems right away. If your not inclined to install any performance mods, (for shame, for shame:cry:) then have the dealer flash the computer for the lastest upgrade if there is one for your car.

[LVMarauder]

I also have this and it pisses me off, it is like u say only under part throttle. The engine is winding up just fine and then BAM it plateaus out. then after about 2-3 seconds starts climbing again. How is this a programming "problem" ?

[CRUZTAKER]

How is this a programming "problem" ?
My guess, and it's only a guess....is that the car HASN'T acted that way since I added the diablo...it must be.

[FordNut]

I also have this and it pisses me off, it is like u say only under part throttle. The engine is winding up just fine and then BAM it plateaus out. then after about 2-3 seconds starts climbing again. How is this a programming "problem" ?

I don't think it is a programming "problem", but rather the program does this intentionally. Seems that most folks with Diablo or DR chips no longer have this issue, but the Superchips Microtuner users still have it. Maybe the Superchips tuner doesn't allow access to these parameters?

Mine was working great with just a DR chip, then when I got the dyno tune in Atlanta the engine performance was improved but apparently the tranny parameters were changed back to stock or something at least milder than what Dennis had programmed into the chip originally. But I know it CAN shift good and it WILL in the near future.

[Krytin]

Yeah - what FordNut said. I don't have the problem if I turn off the overdrive - which I leave off unless I am travelling +55 mph continuously.

[Petrograde]

Seems that most folks with Diablo or DR chips no longer have this issue, but the Superchips Microtuner users still have it. Maybe the Superchips tuner doesn't allow access to these parameters?

That's correct. Mine seems to bog a little less since I got the SCMT,... and sometimes it doesn't bog at all. Maybe it's in how you mash the pedal?

The problem seems to be when the pedal is 3/4 to the floor.

Tom

[studio460]

swc69:

Yup, I've been whining about this "dead spot" on this board for nearly a year now . . . I got an SCT dynotune last year from Jerry--still have the issue. Just got my SCT ProRacer software and tuner/flasher. MANY trans parameters to fool with in the software, and I have no clue to what most of them mean. See your other thread for an example . . .

Oh, and another thing, I do have it at full throttle as well.

[Fourth Horseman]

I have it, too, but haven't tried with OD off. I'll give that a shot today.

[SILVERMARAUDER]

Hey All,

I have a dead spot in the power band at about 3200rpm. When I'm accellerating, when the tach hits 3200 the car bogs for a few seconds, and then takes off again.

Its really annoying. Does everyone have this problem?

Steve C.
2003 300A almost 10k and have not noticed this?

[Fourth Horseman]

I punched it going up the on-ramp to the freeway today, with the OD off. Think I still felt the "flat spot" in the programming. I didn't have a lot of time to play with it as I was late meeting some friends at the pistol range. :) I'll play with it some more, but it seems like OD doesn't make much difference.

[MarauderMark]

I have had a problem with the chip and my trans.i took it out(the chip) and now have noticed that hesitation problem between shifts.hoping when i recieve the new chip this will go away.

[JamesHecker]

Hey... I remember that "dead spot". Used to really bug me. Haven't had it since I installed Dennis' chip!

[TripleTransAm]

I posted something that may be related to what's been discussed, and included some hand-drawn (okay, mouse-drawn) diagrams to illustrate what I was trying to describe.

http://www.mercurymarauder.net/forums/showthread.php?p=105269#post10 5269

While I can't guarantee it just yet without seeing the output of a scantool simultaneously while driving, I think what's happening is either a "too-soon" upshift while the engine is still slipping against the torque converter, or the TCC application comes on at just the moment where the engine RPM and tranny RPM begin to sync somewhat (and therefore the drop in RPM is very slight, but may show up as a 'hesitation' or stumble).

The chip may reprogram the part-throttle upshift points such that they come about at a later speed, where the engine RPM has already gone past the stall speed, so the upshift is felt more as an actual upshift, and not a mushy fluctuation in engine speed (as when the engine is still slipping against the torque converter).

or...

The chip may reprogram the TCC application speed, such that it engages much later when the RPM difference between engine and tranny is even less, so you don't even get to feel the TCC application.

or....

There is some real and present glitch in the factory tables that makes the MM's 4.6l hiccup at that speed of operation, and the chip corrects this.


One way to eliminate the TCC option above is to try the same test when the engine is cold. The PCM will not command the TCC operation when the engine is cold, so if you still get the hesitation, you can effectively discount the second possibility I mentioned above. Possibly even the third (PCM-related), since the engine would be operating in open loop and not using the same operational values as when in closed loop.


Oh, one more possibility just crossed my mind! All that talk of cam clatter due to improper torquing got me wondering if this would trigger the spark retard function due to false knock detection. By the same token, perhaps the MM's 4.6l valvetrain generates some sort of harmonic that the knock sensor picks up as false knock, and the PCM pulls timing in a big way, at that particular RPM? A scan tool would pick this up, showing all sorts of spark retard when this stumble occurred, if it didn't coincide with an upshift.

[swc69]

I haven't tried it with O/D on, since I usually have it turned off when driving around town.

It seems like it would be an ECU issue, so I suspect that those people with chips wouldn't have the problem at all.

But I have to say that its not the kind of thing you have to look for to notice - its really pronounced and very obvious. (At least on my car.) I suppose it wouldn't hurt to ask a dealer about it, although I'll probably get the "they all do that" answer.

Steve C.

[grimmace]

I posted something that may be related to what's been discussed, and included some hand-drawn (okay, mouse-drawn) diagrams to illustrate what I was trying to describe.

http://www.mercurymarauder.net/forums/showthread.php?p=105269#post10 5269

While I can't guarantee it just yet without seeing the output of a scantool simultaneously while driving, I think what's happening is either a "too-soon" upshift while the engine is still slipping against the torque converter, or the TCC application comes on at just the moment where the engine RPM and tranny RPM begin to sync somewhat (and therefore the drop in RPM is very slight, but may show up as a 'hesitation' or stumble).

The chip may reprogram the part-throttle upshift points such that they come about at a later speed, where the engine RPM has already gone past the stall speed, so the upshift is felt more as an actual upshift, and not a mushy fluctuation in engine speed (as when the engine is still slipping against the torque converter).

or...

The chip may reprogram the TCC application speed, such that it engages much later when the RPM difference between engine and tranny is even less, so you don't even get to feel the TCC application.

or....

There is some real and present glitch in the factory tables that makes the MM's 4.6l hiccup at that speed of operation, and the chip corrects this.


One way to eliminate the TCC option above is to try the same test when the engine is cold. The PCM will not command the TCC operation when the engine is cold, so if you still get the hesitation, you can effectively discount the second possibility I mentioned above. Possibly even the third (PCM-related), since the engine would be operating in open loop and not using the same operational values as when in closed loop.


Oh, one more possibility just crossed my mind! All that talk of cam clatter due to improper torquing got me wondering if this would trigger the spark retard function due to false knock detection. By the same token, perhaps the MM's 4.6l valvetrain generates some sort of harmonic that the knock sensor picks up as false knock, and the PCM pulls timing in a big way, at that particular RPM? A scan tool would pick this up, showing all sorts of spark retard when this stumble occurred, if it didn't coincide with an upshift.


IN MY EXPERIENCE WHEN THE CAR IS COLD THERE IS NO DEAD SPOT. IT HAPPENS AS THE CAR WARMS UP. I FIND IT VERY ANNOYING AS WELL. IF YOU TURN THE OVERDRIVE OFF IT IMPROVES BUT ITS STILL NOT PERFECT. FOR THOSE OF YOU WHO HAVE THE CHIP I THINK I READ SOMEWHERE THAT IT IS A PAIN TO PUT IN A '04. IS THIS TRUE? WHAT ELSE DOES THE CHIP IMPROVE?

[CRUZTAKER]

I THINK I READ SOMEWHERE THAT IT IS A PAIN TO PUT IN A '04. IS THIS TRUE? WHAT ELSE DOES THE CHIP IMPROVE?It's a pain because there is no place to plug it it.:P

It improves everything in regards to shifting patterns, timing settings, speed governer delete, and as a bonus...potentially 35 hp.

What SWC69 and others are experiencing is normal, and very addressable in the '03's. Now it's just a case of convincing them. A test drive in a chipped marauder would convince them once and for all.

[grimmace]

It's a pain because there is no place to plug it it.:P

It improves everything in regards to shifting patterns, timing settings, speed governer delete, and as a bonus...potentially 35 hp.

What SWC69 and others are experiencing is normal, and very addressable in the '03's. Now it's just a case of convincing them. A test drive in a chipped marauder would convince them once and for all.


SO HAVING AN '04 I'M PRETTY MUCH STUCK WITH THE CURRENT SHIFT PATTERNS?...IS THERE ANY OTHER WAY TO CORRECT THIS?

[Kelly]

SO HAVING AN '04 I'M PRETTY MUCH STUCK WITH THE CURRENT SHIFT PATTERNS?...IS THERE ANY OTHER WAY TO CORRECT THIS?


I think one of our vendors has a hand held tuner that will work on the '04 :banana:

[CRUZTAKER]

SO HAVING AN '04 I'M PRETTY MUCH STUCK WITH THE CURRENT SHIFT PATTERNS?...IS THERE ANY OTHER WAY TO CORRECT THIS?Call Dennis Reinhart at his shop. His his website and shop phone number is linked in his profile, in the 'VENDOR'S FORUM'.

I know he has been working on a handheld tuner* for the '04's which is a non-volitile mod. ie., no taking things apart. A flash of the eec externally can be done as well**, non-volitile.
*Allows the user to change / restore parameters any time for life.
**A reflash from the dealer could cause a loss of prior tuning info. Bye-bye money and tune.

I actually wish this was available to us back in '02, but back then, we were happy to get anything, plugable or not, to fix these issues. Dennis always came thru in that department with the help of some great Jerry software.

[RF Overlord]

^^^what CRUZTAKER said^^^

[schuvwj]

I do not have a chip but a dyno tune from Jerry and the dead spot is really bad!

Purchased the SCT Custom Tuner from Dennis but not here yet. Hope this fixes it.

[TripleTransAm]

Finally managed to get my Autotap installed... I'm now armed and dangerous, with license to snoop, thanks to Bill Bowker (Marauderer, I believe, no longer with us).

So this issue has been bugging me since NBC Shooter first mentioned it sometime last year. I figured out how to reproduce it, but could never figure out exactly what it was (although I had several theories, as I posted here earlier). Turns out I was semi-correct in one of them, but boy was I unprepared to see exactly what this PCM is programmed to do with the TCC and Tranny shift points!!!!!!!! :eek:

I reproduced the problem, and plotted out the following graph showing engine RPM, TCC duty cycle (%), and PCM-commanded tranny gear.

http://www.tripletransam.com/mm/tech/surge.jpg


What happened here was that I accelerated from a complete stop smoothly at first then adding enough throttle to keep the engine RPM in 2nd gear at just above 3000 RPM... where it kind of hovered until the 'hesitation' happened. I added letters at the top of the chart to illustrate the different stages of the run (up to about 80 kph... close to 50 mph... then back to a stop).

A) Here is the upshift from 1st to 2nd. Nothing exciting to report here.

B) The start of the 'surge' or 'hesitation'. To my surprise (shock?), I see the torque converter clutch duty cycle get bumped up to around 68%. So, under the torque of the engine under power, we see the torque converter clutch begin to flutter on-off-on-off in such a way that it is effectively engaged 68% of the time. Can you say MAJOR SLIPPAGE of that poor clutch? The engine RPM drops a bit because of this, but not a tremendous amount... in another graph I see the speed doesn't drop at all, maybe the speed curve flattens out a bit, but it still climbs.

C) It gets even better here.... as the torque converter clutch is slipping away 68% of the time, the PCM decides it's time for an upshift too! So this point shows the 2-3 upshift coinciding with the PCM's decision to ease up a little on the torque converter clutch application, lowering the duty cycle to about 55% or so. Judging by other logs I took, it seems the PCM has a habit of pulling back on the TCC duty cycle for a bit during an upshift, so this is to be expected, but boy what an unhappy combination of events happening here. Because the poor TCC is slipping about 55% of the time, the increased load on the drivetrain keeps the engine somewhat smothered.

If I had stayed on the gas for a bit longer, the TCC duty cycle might have climbed to 100 eventually, or at least I'd see the engine RPM climbing again, but I backed off.

D) I've backed off, the PCM commands an immediate 3rd-4th gear upshift, and gets slightly confused in that it momentarily wants close to 90% of TCC lockup duty cycle, but then reconsiders and totally unlocks the TCC as I coast down.

E) At this point I've begun hitting the brakes as I approached my parents' driveway (going to pick up my kid, thanks to my wife for patiently holding my laptop). This particular point is a 4-3 downshift as my speed decreases.

F) and G)... both of these are speed-related downshifts, first 3-2 then 2-1 as I pull into the driveway.

H) small RPM rise as I throw the car into Park.


There you have it. A 2-3 upshift under load with the TCC beginning to lockup partially. Damn. Who thought of these tranny shift/lockup points anyway?????

And how long does a pulse-width-modulated Torque Converter Clutch last on these cars anyway? Even my wife doesn't abuse my Honda's manual clutch THIS bad! :confused:

[Mad4Macs]

Do you know of anyone near you that has had Lidios chip/programming installed? A lot of what you said was completely over my head, but as best as I understand about what Lidio did in his programming, my car shouldn't be doing what your graphs show anymore.
DAMN! I'm curious now!

[Marauderjack]

This is exactly what Dennis and I have been fighting with my car......"Slushy" 2-3 shift at part throttle!!! :( Under light to mild acceleration the TC engages after the 2-3 shift.....On moderate acceleration 2-3 shift and TC lock happen all at once and I get a 1000 RPM drop and a crummy feeling and sounding shift!!! :cry:

More throttle at the instant 2-3 shift occurs catches the TC lock and holds it out...sometimes!!! You have to be pretty fast or it engages and then disengages again!!!!!! Sounds and feels crappy :fire:

My other complaint had to do with downshifting and TC unlock which Dennis was able to fix very nicely.....NO MORE LUGGING AND KNOCKING while rounding curves at 1000 RPM's. :up: :up:

I wish there was a way to tie the TC to the O/D switch in such a way as to completely disable the TC lockup with "O/D OFF" and allow it to engage by turning the "O/D ON"????? :( Anybody have any ideas on this??? It would make the car perform so much better!!! :)

BTW....Neither deceleration nor braking unlocks my TC.....Only a "Dennis Installed" 35 MPH unlock code did the trick!!!!

Marauderjack :pimp: