Chevy Vortec Question!

[SGRIM]

We switched out an 05 Chevy Vortec 5.3L block out with an 00 Vortec 5.3L block in a Z71, swapped out intakes and dropped it in...

This truck used to get 19mpg and now with the new motor it is only getting 9mpg

Anyone having any suggestions or thoughts on what could cause such a dramatic difference. I could easily understand 2, 3, 4, or even 5 at most but 9mpg differnce... Something has to be wrong.

No codes and no idiot lights on...

 

[pdzz]

Shane, did you use the injectors off of the 05 or the 00? Do you have some type of scanner that you can monitor 02 sensors and long and short term fuel trim with? Phil.

 

[novaderrik]

somewhere along the line ('02 or '03, i think) they changed the number of teeth on the the reluctor wheel on the crank.. but i think they made the plugs physically different and not interchangeable and moved the location of the crank sensor.

 

[JOHNDEEREGN]

This truck used to get 19mpg and now with the new motor it is only getting 9mpg

but 9mpg differnce...

In Kansas 19 mpg - 9 mpg= 10 mpg difference

 

[Quiky One]

Camshaft, intake, and as someone mentioned already, the teeth on the the reluctor wheel on the crank changed in 2003.

Althought 10MPG is VERY drastic. Check the reluctor wheel first.

Jason

 

[Chuck Leeper]

Nope..

Camshaft, intake, and as someone mentioned already, the teeth on the the reluctor wheel on the crank changed in 2003.

Althought 10MPG is VERY drastic. Check the reluctor wheel first.

Jason

wheel tooth count did not change until, I think 07 on trucks.
24x or 58x.
The crank sensor is just above the starter, and is color coded, either gray or black.
Some reading material:
07 lq9 24 or 58 x crank sensor? = which pcm - LS1TECH
Could be that the engine is running in "cold start" mode.
You didn't change the PCM, or the trans when you did the swap, did you?

 

[xcessiv6]

I think the injectors and spider system is different.

 

[SGRIM]

Thanks guys!

No data stream yet! Truck had to go back to work!

We did it for a friend, so we did what he asked and just swaped out the intake from the old to the new one...

Funny thing is I called a few different chevy dealers and got different answers:frown: So we just did a quick swap... I think we got a mess now though...

I will check out all the stuff you guys posted, I got a feeling this truck may be headed for a trade

 

[novaderrik]

it's a simple thing, but check the temp sender. the ecm might think that the motor is always cold and make it run rich all the time..