6.0 LQ4 stalling when @ operating temp coming to a stop - HELP!!!

[Capt.Throttle]

With the non electronic trans it would be more time consuming to dial in without converter lock in the scanner. Probably had a glitch with the tach, i have some vehicles do excellent with my tach and some do not. Anything from electrical noise to a bad plug wire or weak coil can cause the tach to hiccup even if the engine runs good. Those numbers may not be bad considering the older software version being used.

Interesting observation about the tach signal. This guy had a custom coil pack cable harness that he installed in place of the OEM cable harness to pick up signal for RPM data.

[SiriusC1024]

Burb was on the roller for about 2 hours. There was a lot of idle time, 4 or 5 low speed pulls from idle to maybe 2500 RPM back down to a stop and idle, then 3 or 4 WOT pulls in 2nd gear. I forgot to mention in my build specs that behind the TH400 is an NP203/205 transfer case, then a Corp 14 with 4.88 gears, and 40 inch tires. Final tune dyno sheet is attached, however the layout is garbage because there are no RPM units across the horizontal axis and no HP/TQ values on the right axis.

Attachment 155116

Down a lot of power with the spark tables setup the way they are.

[ns158sl]

That is not a professional tune lol. Why is the idle so high? Dial in the VE then MAF, lower timing a few degrees. The idle over/under spark is too aggressive. I would like to see a stock compare file to compare idle airflow too.

Im confused what they were doing that long on the dyno to look like that?

[Alvin]

There is a lot of janky work out there.

I own a loading dyno.. I only use it for part throttle tuning in a pinch. Nothing beats actual road tuning.

[04silverado6.0]

There is a lot of janky work out there.

I own a loading dyno.. I only use it for part throttle tuning in a pinch. Nothing beats actual road tuning.

You ever heard of steady state tuning? You do need some street tuning to verify work and tweak some drive ability things. Steady state tuning on a loaded dyno is where its at, track tuning is hard to beat at wot though.

[Capt.Throttle]

Ok. Here's this if you want to begin fixing it. Clear LTFT's through scanner then log. Include Idle Adapt (STIT) and LTIT.

Loaded this today. Did not die when coming to a stop or idling in gear, but came close. Definitely an improvement. Added the Idle Adapt (STIT) and LTIT data and took 2 logs... 25 minute more steady state driving (d1) and about an 8 minute drive through the neighborhood (d2).

Appreciate the help. Where do I go from here?

[04silverado6.0]

Have you verified fuel pressure is correct?

[SiriusC1024]

Clear LTFT's, load, log again.

Too soon to tell certainly about fuel pressure being a problem. Be a good idea to verify 58psi, but looks like VE is tracking ok.

[ns158sl]

You should delete half those channels while logging, then add throttle cracker and follower channels. Again cant adjust adaptive AF until fueling is spot on, the MAF is pretty jaggy still.

[04silverado6.0]

Throttle cracker isnt going to function without vss.

[ns158sl]

Ah. Didnt catch that. Well something is pulling the airflow down during a coastdown, ill try and look at it again tomorrow.

[04silverado6.0]

I have successfully set the minimum value for ltit to 0 and raised braf slightly to get a little extra airflow while moving. Not sure that would work either with the vss. Honestly, this may be required without vss if it is trying to pull the idle down during coast and leaving a negative ltit.

[Capt.Throttle]

Clear LTFT's, load, log again.

Too soon to tell certainly about fuel pressure being a problem. Be a good idea to verify 58psi, but looks like VE is tracking ok.

New data logs. Not sure what happened with the first log, scanner just quit capturing data. I tried to get as much stop/go town data as possible. There are two stalls in the d2 log @ the around the 18 & 24 minute marks. Both stalls happened when coasting to stop in 2nd gear. Will try to get a fuel pressure reading some time next week.

Just thought of something... I use a Dakota Digital GPS-50-1 to deliver a GPS based speed signal to the OEM dashboard speedometer (1994 Suburban). Wondering if it would be possible to use this signal to provide input to my ECM for VSS? I have done some searching online but not much out there for 1 guy who supposedly did it to solve a similar issue in a Duramax boat application. It supposedly worked, but it wasn't really clear what OEM ECM he was using or how it solved the problem. Just an idea to consider.

Thanks again for the help.

[gametech]

I have never seen a gps based speed signal that updated fast enough to be of use for any of the pcm calculations. Mind you, just because I have not seen it definitely does not mean it does not exist, but it does make me skeptical.

[Alvin]

You ever heard of steady state tuning? You do need some street tuning to verify work and tweak some drive ability things. Steady state tuning on a loaded dyno is where its at, track tuning is hard to beat at wot though.

I just mentioned I own a loading dyno..

Good luck doing steady state tuning and not having a thermal melt down. It doesn't work as well as you think it would. It's mainly for cars that can't be driven on the road for some reason or another and nothing replaces actually driving the car.


Holding even a moderate load for any amount of time will over heat the exhaust mainly but all sorts of things will run away in temperature. The amount of air moving over and under a car at 35mph even is impossible to reproduce with just fans.

[SiriusC1024]

Will try to get a fuel pressure reading some time next week.

Yeah there's something going on. VE is too low based on corrections, and it's inconsistent between logs. Fuel system problem is possible.

[04silverado6.0]

I have not checked exhust temp while on the dyno but if a car has efans ill command them in the scanner, no ect issues unless its an actual issue with the vehicle.

[Capt.Throttle]

Yeah there's something going on. VE is too low based on corrections, and it's inconsistent between logs. Fuel system problem is possible.

Ordered fuel pressure tester will know PSI in next day or so. I have a new filter/regulator on-hand, but don't want to change anything until I get baseline data.

[04silverado6.0]

What pump and pressure regulator are you running if you havent already mentioned?

[SiriusC1024]

What pump and pressure regulator are you running if you havent already mentioned?

ACDelco 12576341 42lb/hr injectors; Corvette LS1 Inline Fuel Filter Regulator; Walbro GSL392BX 255lph in tank fuel pump