Help Please, on the dyno and rev limiter like problem at ~4600

[johnmaster]

Same issues as here http://forum.efilive.com/showthread.php?11720-Funky-Rev-Limiter-Like-Symptom-GTO
except 99 silverado, cos 5 5.3l speed density, failed maf hitting a wall at 4600 where it seems to be soft limiting the spark, rpm still climbs but power holds dead flat. No maf installed on vehicle, blow through carb so it is not able to pull fuel.

[johnmaster]

Here is the tune file I am using

[johnmaster]

Thinking the way i deleted the maf may be causing the issue, Searching and can't find the details of what is needed to succesfully delete the maf without ill effects.

Spark advance #1 cylinder figure stays strong after it occurs, I would assume it would be pulling fuel as well (but haha-carb so no fuel drop out) and it climbs rpm because it can't kill enough individual sparks to hold it back so hp flatlines from 4600 and up. Feels like "torque management" after that rpm and always has, I knew it had more in it and that was a main reason I took it to the dyno. Now I can figure out why...

Would bad spark plugs cause this issue? Cracked Insulators? Here is another thread with the same issue http://www.hptuners.com/forum/showthread.php?t=30871&page=2

[joecar]

Do you get any DTC's triggering...?

[johnmaster]

Bought new plugs, I can check for dtc's, I am sure my vehicle has a lot of them but they are mostly related to the fact that I no longer am using the fuel injection of the vehicle. I will install the plugs and go for a drive, and make sure the gap is on the tight side.

I need to remember how to work with dtc's again:) Since i killed all of them when I first fired it up last year I haven't had to deal with them.

[GMPX]

Hey John, got your PM at ....... 1:30am my time :mrgreen:
The LS1 PCM doesn't cut spark for RPM limiting, it only uses throttle (if ETC) or fuel for limiting (it's been a while, but I think that is the case). It can certainly pull a lot of advance out to limit power though.

[BLK02WS6]

You need to max out B6614 - that table peaks right at the RPM you are having the issue...

[slows10]

Blow thru carb?? You mean a 4 barrel efi throttle body correct? Are you getting the maf dtcs? Can you post a log?

[johnmaster]

Yes blow through carb, fuel portion of the harness was disconnected, I'm using the pcm simply for spark and trans functions, no maf, its using a 2 bar, cos 5. Thank you for the tip on B6614, my vehicle is not etc but I will change it to see if it helps, certainly can't hurt!

[slows10]

Might as well look at B1201 if we are looking at tables you are probably not using lol. Not really the rpm range you are talking about but what the hell.

[johnmaster]

Thats the spirit! :) funny that 90% of this tune is either irrelevant, disabled, etc and still possibly running into an issue... It coincided with 98-99 mph as well. Could H0109 be the issue?

Should I zero or max 6614 and/or 1201?

http://forum.efilive.com/showthread.php?18216-What-s-the-deal-with-%28B6614%29-Max-Torque-by-RPM

Will try to get an image of the dyno graph soon, it freaks out after 4600 rpm but continues to pull. Hp flattens out perfectly flat.

[BLK02WS6]

From that thread you posted, it appears some OSs need 6614 zeroed... I have never encountered that, the ones I have seen 6614 needed to be maxed - you will have to try both ways I guess. You might not have ETC, but there are settings in the tune that were set to ETC (i.e. the original tune you started with was ETC?). That would cause 6614 to kick in torque management right where you are seeing it go flat...

[johnmaster]

Thank you, I will try it both ways at the track today and see if it effects me either way. Looking back at the day I am now thinking the dyno was simply freaking out playing on some suspicions I had about my tune, Almost 100% positive there is no issue and that I was chasing my tail since only fuel can get pulled and if timing is pulled it would have shown on my #1 cylinder timing pid.

Thank you guys for taking the time to poke at my "issue", hopefully it turns out to be nothing.

[johnmaster]

Now that dyno fever has subsided I looked closer at the data and found it was sampling after the run but mixing the data back into the graph as it coasted back down from let off until the run was ended at 4600-4700 rpm. Happened three times in a row at about the same rpm which was what had us pointing fingers at the truck. Had I not doubted my truck we would have found the glitch and kept tuning, just deleting off the end of the run to clean up the graph. Oh well, small circus all for nothing, going to the track tonight to see what it really does, more boost, more timing!

[joecar]

Stuff happens... running at the track is the final word.

[johnmaster]

Indeed, can't drive a dyno!