Just finished my 4.8l install after alot of crap, it runs but runs like crap, any ideas? I got my tune from Jesse at Wait4me Performance, I have like 50+ PSI fuel pressure at the rail, it is an 05 4.8 with 02 DBC intake and stuff on it.

Thanks Guys

 

could you describe the problems your having in a bit more detail?

 

Is this the first time you've had it running in the swap car? Or did it run fine before and is giving problems post tune?

 

This is the way it started, 1st run. it just doesnt have ANY power at all, it runs fine at idle and when you hit the gas, it just feels bogged down and sluggish. the tune was done a while ago.

 

You should have 58 PSI at the rail. Less than that and the engine will do all sorts of weird stuff. One key on / off cycle should net 58 PSI and it should hold that while not running. Eventually it will leak down but you should be able to watch for a minute or two and not have much drop.

Is your MAF plugged in? Do you have any codes? Is you wiring correct and WELL grounded?

I know it sounds stupid and obvious but if your voltage is low and / or your battery terminals aren't up to par, the engine will likely run like dog poo. The alternator should be charging between 13.2 and 14.4 volts with the engine running...

Not trying to sound like a know it all but I can't emphasize the importance of good grounds, good electrical connections and proper fuel pressure. If you are having electrical or slight fuel pressure issues (especially if they are intermittent) you may not get codes.

 

Start over....
Give all details of the donor engine/trans, what you transplanted it into, what sensors your running or not, etc..
My engine/tune sucks doesn't help.

 

What does the fuel pressure do when you give it gas? When you say 50ish, exactly how much do you have? What kind of fuel setup are you running?

It starts so that's good, sounds like it's starving for gas to me......

T,

 

The computer, injectors are all tuned to be at 58psi.. less then 58psi would explain why idle is good. but as soon as you hit the gas a bit.. there is not enough fuel being sprayed and you are most likely having a lean condition.

As some electrical expert once told me.. 99% of electrical problem are bad grounds. So.. having good grounds were needed is a Requirement ! not a I guess this will work !

So.. what eveyone is getting to and saying. Start at the beginning if you expect help from us. And make sure all fuel and electrical requiremetns for the engine are meet (Fuel pressure, Battery voltage, etc). Check for vacuum leaks also...

Good luck..

P.s... i have a jessie mail tune also, it fire right up 1st time and have had no problem (but could really use a dyno tune for that last bit of power)

 

Look here.
Im having the same problem and same pcm tuned by Jesse @ waitforme. Take your time to read.

https://ls1tech.com/forums/generatio...situation.html

 

I have 54psi at the rail, but it fluctuates too, the engine is running like the timing is way off, in the computer, the o2 sensors dont show a code and they are not installed. when i take the plug off the MAF sensor, no codes at all, nothing changes. I made sure the engine grounds are clean and tight, one on each side of the engine to the frame, the harness ground behind the intake cleaned and tightened.

the engine runs bad at idle too, like the timing is way off. but also wont get out of its own way. my mechanic says all other sensors are correct.

no codes are set at all, that is weird

 

Was the 05 computer used?
Could be that the computer is not capable of running a cable operated TB, and you would need an earlier computer.

 

the engine is an 05, but the pcm/harness/intake/sensors and fuel rail is 02

 

the '05 4.8 isn't a 58X tooth reluctoris it?

 

supposed to be the same from 99-07 early ( old body style) the blocks are all the same. that is confirmed by Hot Rod Lane website.

 

Go by sensor color. Black is 24x, gray 58x

 

I am getting that looked at now, if it is a 58 do I need to change the harness and pcm? What is the best/easiest avenue to go?

 

I found this info on

http://www.fbparts.com/ls_general_info.htm



The 4.8L crankshaft is an iron crankshaft with 2.1” rod journals and 2.65” main journals. The stroke is 3.267” and is designed to work with a connecting rod length of 6.275”. They started out with a 24-tooth reluctor wheel and this was used through the 2007 model year in the classic 800 series trucks. However, in 2007 starting with the 900 series full size truck, they were changed to the 58-tooth reluctor wheel.

 

Exactly the same happening here. Now the more and more I look at it, the pcm is to blame. Ill know for sure this week-end.
Clyde65, when did you buy that computer? I think I bought mine early december 2009.

 

I got it when I got my motor in August 2009. Just doesnt make sense to me.... If I had another "stock" computer without a tune, what would the engine do? run then die?

BTW what does it look like when the rear o2's are removed in the tune? By what my mechanic says he doesnt think they are removed.

 

Shouldnt change a thing. They have nothing to do with how the engine is running. I think we both have defective units.