gregX10A

Hey guys im tring to finish up my ls1 swap on my 89 firebird and im having an issue with the car wanting to drive itself. It was doing this before and after lmr tuned it and was hoping getting it tuned would take care of it. A few seconds or so after letting off the brake at idle it would begin to accelerate up to 30mph and drive itself down the road. Iam right now taking off my intake and checking for leaks and resealing everything. I have noiticed that there are divets on the bottom of my fast intake from my arp head bolts. Any input would be greatly appreciated.
Here is my set up:
rebuilt 98 ls1 short block
prc ls6 stage 2.5 heads
Tsp torquer v2 cam 112lsa
Fast lsxr 102/102
4l60e
circle d 245mm 3200-3400 stall torque converter
01 fbody pcm

thunderstruck507

iTrader: (18)

Check for vacuum leaks and check for throttle position signal to be showing 0% when you aren't on the throttle.

My guess is a vacuum leak and I am surprised it wasn't noticed during the tune. If it is a leak, you will want to have the tune looked at once it's fixed.

Another possibility is that the converter is too tight for the combo. What is the idle RPM set at?

gregX10A

Thanks for the info, ill let you know what i find when i get it back together. Ill also note that when i was taking the intake out i noiticed that lmr drilled a hole in my throttle plate and neglected to ask or tell me about it.

SickZ28

iTrader: (8)

if you can't get the RPM down by locating any vacuum leaks or pin point the source of the problem try to plug the throttle body butterfly plate breather hole with a rivet. My setup pulls more air that i want which causes my rpm's to be a bit higher thus making the car accelerate a bit, once i plug the throttle body plate hole with a rivet problem solve. RPM's are at normal settings and everything running beautiful.

Also not sure which intake your running but if you got an EGR check the EGR tube that inserts on top of the intake right behind the throttle body. The EGR gasket might of moved and its sucking in air. Just a thought as i'm not sure what intake your running.

SickZ28

iTrader: (8)

LS1 throttle plates come with a hole already, do you mean an additional hole was made or was the hole drilled larger.

If so follow my previous post and its fixable with a large rivet (one that fits perfectly within the hole)

gregX10A

The intake i have is the fast lsxr 102 intake and i have the 102 tb. no egr. the throttle body didnt have a hole in it when i took it to lmr but it had one after i got it home and took it apart ( had to clean up the burs from where they drilled). Thanks for the tip on the rivet. ill see what i find when i get it back together

SickZ28

iTrader: (8)

thats a bummer, i highly believe that is your issue as my car was doing the same thing until i plugged the hole with a rivet.

thunderstruck507

iTrader: (18)

same here, bought the TB used and previous owner had drilled a hole

but you said it was doing the same thing pre-tune so it might not be the issue

SickZ28

iTrader: (8)

Hmmm if it was doing this before LMR tuned it then why would LMR drill a hole making things much worse. lol

gregX10A

thats what im tring to figure out. lol When i was there on the first day they said the iac was being intermittently inconsistent and the motor would want to idle up and then catch itself and would want to stall

z28SSilvest

I would say either clean behind and around the throttle body if you haven't already.

is your car auto or manual?

gregX10A

automatic. im about to go and work on it

wait4me

iTrader: (10)

It is the throttle cracker table in the tune itself causing the issue, or the main desired airflow value.

Simple fix in the calibration is needed.

gregX10A

i wish i could tell u what lmr did but they didnt really give me to much info on the tune and there wasnt really anyone there to answer my questions when i picked the car up. I talked to a Patrick Guerra and he tried to explain to me about some of the tables that need to be adjusted for idle. Im sorry i cant be of anymore help with the tune info as this is still new to me since im coming from a 350 tpi to a ls1 im still learning

HioSSilver

iTrader: (8)

If it's a cheap throttle body it may need some work. I had to put epoxy around my tb blade to get it to seal so the iac would work properly. My issue was very similar to yours.

gregX10A

I have a fast 102mm throttle body

crazyelf

iTrader: (21)

Did everybody miss that part? Your head bolts shouldnt be contacting any part of your intake, So I assume your speaking of the valley cover bolts. You need low profile bolts so that they don't contact and CRACK the bottom of your fast intake. Which it very well may have already or they could be keeping you from torquing the intake down properly and getting a good seal.

gregX10A

I installed the button head bolts that came with the intake on the valley cover. The bolts I'm referring to are the small cylinder head bolts at top of the head. I have arp bolts and the washes push the bolt up a little hitting the bottom of the intake. I filed down those areas so it would clear. I got my intake and throttle body back on and I tripled checked everything to make sure it was sealed good and torqued down good. All vacuum lines are good to.

gregX10A

Alright, so I got home from work today and finished hooking everything up. I rechecked everything one more time and it looks all good. I got my Dakota digital tach interface today and I got that hooked up and programmed. Started the car up and it started idling. My dad said it was idling kinda high. If the tach was reading correct than it was idling at 1500 rpm. Won't know how accurate it is till I get a scan tool that can read live data. Haven't blocked the hole in throttle body yet so that may be y the idle is so high and the tune is probaly more than likely off

gregX10A

Update!!! I trailered my car to Victoria to have Patrick gurrea take a look at the tune and it was off. Patrick took the time to redo the tune and get it right. I'm very pleased with the results and can't wait to get it redynotuned after getting the motor a little more broken in. Thanks everyone for your input and advice.