i've been recently experiencing this issue, which became apparent during a race where i shifted the car above 6k rpms. around 6k it kind of fell on it's face and apon shifting (manual valve body, i shift the car) in 2nd gear it took a couple seconds to re-gain it's power, almost like the car was still sputtering and then took off again.

i've been logging it with HPTUNERS and have found nothing out of the ordinary, besides my maf lbs/min drops dramatically when the loss of power happens. not sure if it drops before or after the car "breaks up" or cuts off however.

dfco fuel cutoff is set at 6400rpms and resets at 6390 rpms in all of the tables. i swapped out the maf sensor for an old one i had lying around and it has the same problem, nothing changed.

this problem sort of just happened out of the blue, and it unexplainable according to my logs, there is no knock, and everything seems to be functioning properly like the injectors, o2's etc.. timing DOES drop out when the breaking up happens, but i was thinking that was due to the drop in the maf lbs/min.

any advice on WHAT to log, or what to check out? i was thinking it is just worn out valve springs and the valves begin to float at that rpm, which is causing an extreme decrease in airflow which is why i see the maf drop off. doesn't make complete sense but im stumped at this one. maybe bent pushrod(s), or something else??

i also tried to log maf HZ (hertz) and it would just sit at 0 hz. maybe both maf's are bad or what? or maybe a glitch in the software which doesn't allow the logging of hz.

plugs are practically new, wires were replaced not too long ago.

the problem ALWAYS happens around the same rpm point, 6k rpms.

ANY suggestions appreciated.

it is driving me nuts because with the new gears im running hitting the first gear shift before 6k on the nitrous is gonna be almost impossible. it just comes too fast, and i believe this condition is what caused me to burn a plug while on the nitrous last season. it is like something is causing the fuel to cut off but nothing that i can find!!

 

I did not see this mentioned in your list of things but are you still on the stock abuse mode, or have you changed it. Im not sure if this is causing your problem, but you can look into it and maybe change the abuse setting and see if you have the same issue.

 

Maybe it's time for a new fuel filter? But that I
think would show you some KR & a lean signature.

If the airflow drops and dynamic cylinder air drops
that would index you to a higher advance, in any
normal-profile spark table. If timing drops it's more
likely a reaction to something. If not KR, then some
other spark retard element; log 'em all and see who.

An outside chance is that you have some sensor
/ connector / wiring loose, that just happens to
like to rattle at the 6000Hz engine note. If the
ECT / IAT value were to jitter around, it would
jack timing (and possibly fuel).

I would log injector PW to see if it's flaking as
well. There are some mixture advance things, and
if fuel is cutting then spark may follow.

 

The problem we have found with gear changes is the rpm is different then the speed for some reason, even though we correct the gear change with HPtuners. hope this helps.
the speed and rpm have to be exact, like on the truck it is set at 6800 1-2 we found the mph to be 44, if you can get both of them set up the same you should be fine.

 

posting your file would definitly help in identifying any undersying problems in the tune. FWIW the scanner should have no problems scanning maf in hz if it is there might possibly be something wrong with your maf.

 

i have to figure out how to post the file- but if i should be able to log hz then im thinking it is the maf being bad.

abuse mode= off and has been since i've first tuned the car. the rpm vs. mph tables don't apply since the vss isn't even hooked up- the codes are all disabled as im running the th400 with the rmvb.

as far as the timing, i gotta check again because i THOUGHT it was dropping out, but i could be wrong and it didn't. if it doesn't make sense that the timing would drop out if the maf lbs/min dropped out then maybe i was looking at the wrong value.

 

Check that the MAF receives +12V and puts out
something about 5V at idle and decreasing with
load. These can be done with a DMM and show if
it's a MAF problem (output does not change w/
load), care & feeding problem (12V) or just a
scanner PID that does not match the vehicle (in
some cases there are multiple versions, some for
other vehicles / setups etc.). The scanner should
validate available / sensible PIDs but using a stale
or someone else's config might point at one that's
not.

 

i know it is going to be hard to diagnose until i figure out how to upload the bin and some logs-

just now i went out and took .05 out of the PE just to see if it helped any. it was a tad rich last time i dyno'd it (12.4 :1) so i know it wouldn't hurt anything to play around with it a little bit.

it DID help the issue some. not sure if it is related or not since i didn't test the car out today before i leaned it out- so a malfunctioning sensor or lose connection could still be a culpret. i did also go over all of the injectors and coils, coolant temp sensor plug, maf plug, iat sensor plug just to see that they were all properly clipped in, nothing stupid like a broken wire and i found nothing. all was well.

now it crackles a little bit around 6250 or so, but if i shift it is immediately back in the power and the car doesn't hesitate for the full second or 2 that it used to.

still stumped as to why anything happens before the rev limiter however- which is set at 6400.

 

Check you speed limiter in the Speedo section
Max. your torque thresholds in the engine torque management section
Alter your TPS MAP error limiters to min. and max. values respectively

But a copy of your tune would help, as foff said...