i've recently done a ls1 5.7 swap into my 2001 chevy pickup. now, i ask this question on LS1Tech because i think these are engine issues, not truck side, and this is the site to go to for LS1 questions

What i have:
2001 silverado (use to be 4.3)
2001 z28 Ls1 engine, accessories
truck 4l60e
truck TQ (from 4.3)
Custom built wiring harness
Z06 MAF
first of a line intake


here's the list of problems i'm having:

1. rough idle
2. when shifting from drive to reverse (or other way around) i have to sit it in nuteral for a bit...cuz the truck will rev up real high, 2000 rpm - 3000 rpms, between those shifts
3. there is a "flat spot" i get when driving. usually between 40 mph and 50 mph...i can stomp on the gas and it won't down shift....it'll stay in 4th gear. but i don't have to stomp on it to do it..it'll "bog out" just normal driving too. this happens only about 75% of the time. the rest of the time it'll shift and accelerate fine.
4. code p0121
5. MAP sensor reading flat, like 13.6 or something

here's what we've tried:

replace tranny, but not TQ
Hours of re-tuning to try to see if it's a tuning issue
replaced the TPS

What we think it might be:
Trottle Body
Map Sensor
TQ

Anyone have ANY thoughts??

 

first, what PCM or tuning is in the truck? generally the stock 4.8/5.3 tune will run an LS1 fairly well, but i dont know whats in there
second, are you certain there are no vacuum leaks, sounds like you could have one,which intake are you using?
map sensor could be junk
did the tps sensor code came back after you tried a new one?
hows FSC, i havent been over there for a while?

 

i think it's a re-flashed 5.7 PCM, re-tuned using HP tuners, set off a Z06.

I'm pretty sure thre's no vacuum leaks...sprayed either all around looking for one a while back

I'm using stock 5.7 intake

TPS code came right back after the Sensor swap.

FSC is good same ol' clowns like me :LOL:

 

i read this on another forum:

"I recently swapped out my Gran MAFS and put back my stock one.

I now have a "dead spot" at around 50 mph-65mph where if I slowly apply more gas nothing happens. I hear more noise as if I'm getting more air, but my truck just doesn't do anything. If I keep pressing down on the pedal, at some point it downshifts and takes off. Whats happenin'?"

Do you think a bad MAF could cause this prob?

 

run in mafless, SD tune for a while and see if that helps. also try disabling closed loop with hp tuners scanner.

 

if youre still in tucson bring the truck up to us... I will get our tuner in here to peak at it and see if he sees anything wrong... in addiiton we have numerous LS1 parts laying around incase something accidently broke during the swap or if something small is just missing!

 

wrong onyx i'm in san antonio...but i do apperciate the offer

 

any other thoughts??

 

Have you done real-time tuning while driving? Have someone sit in the car with the tuning laptop while you're driving in that dead spot and see what's going on.