Stalls on stop - NO MAF, VSS, PNR1234

[BryanD]

This is a transplant into a Toyota Landcruiser.

NOTES -------------------------
Engine: 2006 LQ4 6.0L
Cam: Z06
Transmission: TH350
MAF: None

Without VSS or PNR1234 switch the ECM thinks its in 2nd gear, 0 mph all the time.

The engine will rarely, but sometimes stall when coming to a stop. Target idle is set to 700rpm. Scanned rpm often shows 500, 450, 300, etc. when braking and coming to a stop. more pronounced when hard breaking too.

A NO-MAF in car tune was performed and am COMPLETELY happy with every aspect of the performance except this "once in awhile" stalling issue.

Have played with Proportional & Derivative Idle settings (to about a 20% change) to try and increase the response time to maintain the 700 idle, but nothing seems to even make a slight difference.

Have increased Base Running Airflow until a "hunting" idle occurs and rpm's still drop. have noticed TPS at 1% right before low idle condition.

Have played with the Stall Saver, but once again nothing seems to help.

is there any way to "trick" the ECM to maintain the 700rpm without a VSS or PNR1234 switch?

[edcmat-l1]

This is a transplant into a Toyota Landcruiser.

NOTES -------------------------
Engine: 2006 LQ4 6.0L
Cam: Z06
Transmission: TH350
MAF: None

Without VSS or PNR1234 switch the ECM thinks its in 2nd gear, 0 mph all the time.

The engine will rarely, but sometimes stall when coming to a stop. Target idle is set to 700rpm. Scanned rpm often shows 500, 450, 300, etc. when braking and coming to a stop. more pronounced when hard breaking too.

A NO-MAF in car tune was performed and am COMPLETELY happy with every aspect of the performance except this "once in awhile" stalling issue.

Have played with Proportional & Derivative Idle settings (to about a 20% change) to try and increase the response time to maintain the 700 idle, but nothing seems to even make a slight difference.

Have increased Base Running Airflow until a "hunting" idle occurs and rpm's still drop. have noticed TPS at 1% right before low idle condition.

Have played with the Stall Saver, but once again nothing seems to help.

is there any way to "trick" the ECM to maintain the 700rpm without a VSS or PNR1234 switch?

Tune and a data log..............

[BryanD]

Darn it, i forgot to save any of the logs. unfortunately it is a friends vehicle and he is some 50 miles away. i've already made the trek several times now. hoping to have something concrete to try next time

but here is the latest tune i'm using.

[jakebdb56]

There may be some other trickery to fix it without a VSS, but increasing idle airflow around your operating temperature will help maintain idle. I've had to do the same thing with a friend's Camaro with a TH350.

The VE table could probably be smoothed out a little around 35-80kpa. In cases like this I'll usually copy over the 800 RPM column to the 400 column so if the threshold is met where the PCM will step down a cell you won't necessarily jump from say 71 to 56 on the VE.

Another thing you may look at too if it's a once in a while deal, fuel pressure. Had this happen on a truck before.

[BryanD]

another thing we noticed is; altitude makes it worse. at my house (4500ft) I couldn't get it to actually die. rpm's would drop into the high 400's but not die. take it to his house at 6500ft and it will drop to 300 and below and sometimes die.

I did think about the fuel pressure and also voltage. will check that for sure next time.

[jakebdb56]

I wonder if your'e hitting a certain area in the VE then that's making it not want to run. Can you post a log?

[BryanD]

I wonder if your'e hitting a certain area in the VE then that's making it not want to run. Can you post a log?

i didn't save any of the logs. i plan on another tune session for this problem next Monday. i will definitely save it & post it.

[BryanD]

There may be some other trickery to fix it without a VSS, but increasing idle airflow around your operating temperature will help maintain idle. I've had to do the same thing with a friend's Camaro with a TH350.

The VE table could probably be smoothed out a little around 35-80kpa. In cases like this I'll usually copy over the 800 RPM column to the 400 column so if the threshold is met where the PCM will step down a cell you won't necessarily jump from say 71 to 56 on the VE.

Another thing you may look at too if it's a once in a while deal, fuel pressure. Had this happen on a truck before.

update: found a fix!

i did increase the 400 column of the VE table to about 90% of the 800 column and smoothed both. but honestly, it didn't make any big difference. but it is the VE table i ended up using.

what did make a HUGE difference, and has appeared to solve the problem is; i disabled the "Proportional" & "Integral" Idle RPM tables. I did this by increasing the "enable rpm error" box to 2000 (a situation that would never happen).

Although it was my understanding that these are "adder" tables, they affect the idle in an adverse way in my situation. without the VSS, MAF, & PNR1234 sensors the ECM thinks its in 2nd gear & Zero mph all the time. it is my speculation that; sitting a Zero mph, the engine still idling at 800-900 rolling to a stop, these tables "subtract" airflow in an effort to slow the engine. and as you roll to a stop and the rpm's do come down it doesn't react fast enough in the positive direction. remember it thinks its a 0mph all the time!

anyhow i did learn a lot getting through this problem. also, i tried disabling the "adaptive idle" function also, but that made no difference, so it is running with stock parameters.

and, with the Z06 cam, 10%+ Base Running Airflow increase helped dial in, and maintain the idle as everyone said and was a reasonable thing to do.

thanks for the help guys!

[bad6as]

update: found a fix!

i did increase the 400 column of the VE table to about 90% of the 800 column and smoothed both. but honestly, it didn't make any big difference. but it is the VE table i ended up using.

what did make a HUGE difference, and has appeared to solve the problem is; i disabled the "Proportional" & "Integral" Idle RPM tables. I did this by increasing the "enable rpm error" box to 2000 (a situation that would never happen).

Although it was my understanding that these are "adder" tables, they affect the idle in an adverse way in my situation. without the VSS, MAF, & PNR1234 sensors the ECM thinks its in 2nd gear & Zero mph all the time. it is my speculation that; sitting a Zero mph, the engine still idling at 800-900 rolling to a stop, these tables "subtract" airflow in an effort to slow the engine. and as you roll to a stop and the rpm's do come down it doesn't react fast enough in the positive direction. remember it thinks its a 0mph all the time!

anyhow i did learn a lot getting through this problem. also, i tried disabling the "adaptive idle" function also, but that made no difference, so it is running with stock parameters.

and, with the Z06 cam, 10%+ Base Running Airflow increase helped dial in, and maintain the idle as everyone said and was a reasonable thing to do.

thanks for the help guys!

I belive this is the same problem I'm having. No VSS and a th400 transmission so my pcm is always reporting 0mph and in D4. So when coasting after a pull or letting off after a burnout the adaptive idle kids in immediatelyand starts pulling air out by closing the icv. So by raising the error rpm to alot higher value this slows down when adaptive idle starts closing the icv