formula218

iTrader: (2)

i put a 5.3 into my '94 firebird, but my speedometer is reading about 30-35mph while i'm going 70mph, is this something in the tune that we missed?

i'm also having a high idle issue, it's idling at about 1500rpms and sometimes goes down to about 1000rpms. i thought IAC but i swapped it out with a new one and it still isles high.

thanks for any advice guys, much appreciated.

sierravmax

iTrader: (1)

T56 or auto? I would check for vacuum leaks causing the high idle. Computer most likely has to be tuned for the speedo. Also are you running a egr? Throwing any codes?

I am having the same issue as you with the speedo. I have been just using my gps. I need to get it fixed some time soon.

formula218

iTrader: (2)

T56. i sprayed starter fluid around looking for a vac leak and couldn't find anything, i'll try again.

i think something needs to be done in HPT for the speed, i'm just not sure what. i believe we had to change the value of something to get the RPMs correct.

No EGR, only code is for EGR.

sierravmax

iTrader: (1)

Did you hook up the small vacuum port on the back of the intake? Have you hooked up the vacuum canister and vacuum line going to blower housing? Any exhaust leaks? I can't help much for the tuning as I had someone do mine. I know he set the rpm value at 3. He also deleted my Egr and A.I.R from the computer.

formula218

iTrader: (2)

yes on the back port by the MAP sensor, i don't know about the vac line to the bell housing, no exhaust leaks because it's open headers right now, our wonderful MI roads thought my exhaust was too quiet and stole my Y-pipe back.

bczee

iTrader: (12)

Use HPT to verify the VSS ppm.

Most likey the Firebird speedo is set up for a higher value and the trans VSS is a lower output count. Might be able to adjust the pcm to speedo ppm.

That would be suggestion.

jmd

iTrader: (4)

Could be.
Auto VSS reluctor is 40 tooth.
Most GM T56 reluctors are 17 tooth.

sierravmax

iTrader: (1)

My car was a auto with the Lt1. Then when I did my Ls swap I swapped to t56.

jcvett56

Update gear ratio and tire size in tune. If your file in PCM is for auto and you have a manual idk if/what you can change to make the PPM match properly. If you can't change anything then upload a manual file in computer that's close to your setup and update tune accordingly.

LS1MCSS

iTrader: (18)

The problem is most likely in the tire size and gear ratio settings in the tune. The speedometer is expecting 4K pulses per mile and when everything is set right in the tune, that's what the pcm will output.

formula218

iTrader: (2)

i know it's already been adjusted for tires and gear, that was one of the first things he asked. unless maybe we used the wrong gear ratio, but it's a stock rear and we went off the RPO sticker.

jcvett56

Sounds like you need a manual file uploaded into PCM then. Then upload your gear ratio and tire size.

sierravmax

iTrader: (1)

I recently did a test. I drove my car at 20mph per the speedo and my GPS said I was going 42mph. Then I did it again at 30mph and the gps said 64mph. I then pulled my computer and sent it off to a different tuner. He just got back to me and told me I had a tune for a automatic Silverado. lol Anyhow he is reflashing it for a manual Fbody and hopefully everything will be fine when I get it back.

Project GatTagO

iTrader: (7)

Your ECU is most likely set for the 40 tooth auto trans gear, and you need to change it to the 17 tooth T56 gear.

Andrew