Hello everyone,

I have a 4.8 build I can't get right to save my life. Build specifications are stock 2000 4.8, Turbo 400, Stock PCM, Siemen Deka 80s, 78/75 Turbo running on Speed Density with a 2 Bar Map.

I had a reputable tuner do a base tune on the truck to get it up and running. It ran and idled great, however when you would go to drive it the truck wouldn't want to go over a certain RPM range and would sometimes die after coming to a stop. After getting a log we decided that he forgot to turn off abuse mode. However, in that log we found out that I forgot to plug in the IAT sensor. After plugging in the IAT sensor the truck runs like absolute garbage. Unplug the IAT and it runs relatively fine idling a little high and having the idle stick occasionally. I have gotten a log, which I can post with the IAT plugged in and after having my tuner and another tuner look at it nothing seems too out of the ordinary and it looks like the truck should be running fine, but it's not. You have to pedal it to get it started most of the time, and have to pedal it for it to stay running so it doesn't die. And when it does want to idle on its own without pedal, the idle will be anywhere from 400-1,200. Along with the log looking good, I have also tried a leaner tune, a richer tune, checked for vacuum leaks over and over, checked for fuel pressure, tried 3 different IACs, 3 different IATs, a TPS, read plugs, checked injectors, all to no avail. The truck also has no codes.

I am at a complete lost, I have been fighting this issue in my spare time for the past couple of months and I really want to get it right before I have to put it in storage for the winter. I will post the tune file and the logs below, if I can figure out how. Any suggestions are appreciated.

Thank you!

 

Disconnected ie open circuit IAT will command -40 degrees temp compensation from ECM.
IF your "Tuner" built a fuel map (VE table) with OPEN CIRCUIT IAT, you need to do two things:
1) fire your tuner.
2) Build a new VE table.
.
Do not despair. 4.8 is A: the toughest most durable gasoline engine since the slant six.
B: Tuning "window" with 4.8 is very wide due to short stroke, small bore, LONG rods. Basicly as close to bullet proof as any V8 engine inexistence.

 

Almost everything about that tune is nonsense garbage. I have no idea why somebody would try to scale a tune without knowing how to make a good tune without scaling. You desperately need to go back to the original stock file and start over.

 

Gametech,

Lovely. I know little to nothing about tuning which is why I paid a rather well known and high regarded tuner here in the midwest $300 for the base file. That is extremely aggravating and unfortunate, all the while he has been telling me "everything looks good.".

 

You are running DEKA 80# injectors, and your "Tuner" has your injector flow rate at 51.7 Lb/Hr. That, coupled with your PEAK VE 'numbers' being 55, compensating for incorrect injector flow data suggests that your "Tuner" should not quit his day job.

IF he tuned the motor to " RUN" with OPEN Circuit IAT, which is equivalent to MINUS 40 degrees, THAN it will certainly be a bit OFF when actual ambient temperature is used to modify fuelling.

I see some pretty funny idle airflow settings, looks a little high for a 4.8 liter.
I'd strongly recommend getting your own HPTuners interface, eat the credits, and tune it yourself. You'll have plenty of time to learn.
4.8 is a pretty tough- and forgiving motor.

 

A motor that won't rev, won't idle, needs pedal to crank, and dies when you come to a stop has serious issues that would be obvious to any competent tuner. Even if it had a reasonable tune (which is absolutely not the case), mechanical issues would be obvious from log files. Telling you everything looks good tells me you got ripped off by somebody who does not even care enough to make up something to tell you.

 

The injector size is smaller because he was trying to scale the tune. I have deka 80's and my injector flow rate is set at 40 or 50 (don't remember). When you scale a tune, just scaling the engine size and cylinder displacement does not do it.

 

.
.
. . . . . NAME the author of your 300 dollar "Tune"..

 

"why I paid a rather well known and high regarded tuner here in the midwest $300"...
He charges by the fukups.. $30 each.
Not unusual. Around here, the local "hotshit tuner" is $600, and a dyno pull is $250 more. All to get a shitty tune that wouldn't run well enough to pull the car onto the trailer.
Time to learn to do your own.

 

About 20 years ago I had a guy "tune" my silverado to bypass the add-on whipple piggyback that came with their blower. He put in a canned tune that may or may not have been stolen from the internet, hooked up the blower bypass to never shut so I only got 2lbs of boost, and disconnected the turn on wire for my electric fans. I bought my own tuning software and never looked back.

 

Did you actually make sure that you have a 2 bar Map sensor? What is the map reading at key on---engine off?
Are you still using the Maf? In Airflow, Maf shows 14500hz, Dynamic air shows over 8000. Are you running SD or blended?