need help from keeping my rebuilt motor from dying...
 

ok guys, i got my newly rebuilt streetported engine started twice but it's very hard hard to keep a steady idle. it dies out when i let my foot off the gas and the rpms fall really fast which could be attributed to my 9.5 lb flywheel. what screw(s) can i adjust to keep it from dying? I also have a pfc with base mod map which i will use to break in the motor. My mods are all the bolt ons with full non sequential twins. thanks in advance.

I've got a healthy streetport on my engine too, but it started up and purred like a hungry pussy when I first fired it up. I am sure your light flywheel doesn't help, but it sounds like you have a LOT more going on there....
How are your injectors and all that? What ECU are you running?

hi, ive got an apex power fc with base mod map. my vta1 value is .80 and my vta2 value is 1.79. would these tps figures cause the dying? i've got 1300cc secondaries but i changed the figure on the commander to reflect that.

Youor secondaries aren't even firing anyway...... Sounds like you need to adjust your throttle body screws or you might have a massive vac leak.......

As per page F-182 in the FSM:

narrow range---fully closed, 0.75 to 1.25V//closed to open, 1.0 to 5.0V//fully open, 4.8 to 5.0V
full range---fully closed, 0.1 to 0.7V//closed to open, 0.4 to 4.3V//fully open 4.2 to 4.6V

(I think VTA1 is narrow range and VTA2 is full range on the pfc commander, but without having it in front me I can't be sure.)

You want to check all of this with the motor warmed up, but shut off. Have the key in the 'accessory' position, and rotate the linkage by hand. Also, you'll want to reset the ecu by disconnecting the ground on the battery for at least 20 seconds and depressing the brake pedal.

should have nothing to do with the flywheel. my 8.5lb has never even caused me to stall out. it must be either a vac leak or some sort of fuel problem. if you havent adjusted your tps and your car ran properly before the motor swap do not touch your tps! i adjusted mine to the specs and it acually runs consideralbly worse. i would have someone look over the map and in the free time look for vac leaks. does the car at least stay running if you get it to 1500-2k?

Rich is right, make sure your TPS is calibrated...with your engine being in and out.
but to answer your question, there is an idle screw on the front of the TB, that you can tighten to allow more air to seep past the primary butterfly (IIRC)...you will notice the screw pushes down on the linkage the throttle cable connects to.

I actually transfered my TPS to a polished TB. My values for vta1 are.79 and for vta2, 1.75. Would this cause the problem? Regardless, those values are out of spec and I'm gonna have to adjust it.

tps or idle adjust screw under the throttle body!

yea, screwed that one under the TB all the way in and screwed the vertical one quite a ways down, hopefully that'll keep the car idle. gonna start it again tomorrow, thanks for the replies fellas. :)

I have seen this happen on a 2nd gen when my buddy installed his lightweight flywheel. stock ECU and he also installed the RB full exhaust (engine back, true dual) along with an intake of some sort from RB. It would die out if he didn't leave it in gear as he came to a stop. if he let it fall from high rpm, it would stall out.

yep...especially when changing TB's, the TPS must be calibrated. Your ECU and MAP aren't on the same team yet ;)

^ i know you are much smarter than i am... yet if he had the pfc and the tps sensor has not been messed with and the car ran properly before i would not move it. the air bleed screw can be adjusted to help with idle. and he might want to reset his idle via the cable. i had references that were slightly out of spec and the car ran quite well... not perfect but it ran well. i then adjusted the tps to be within specs and the car runs worse now. i guess if the specs are way out then change it but i would write down your specs you have before you change it so you can go back.

i honestly think theres a massive vaccume leak somewhere that is causing it to die right out. if he can get it to stay running at an rpm i would use some carb cleaner to check for vac leaks. or just check for some vac lines that are not connected. some motors dont have to good compression on startup so any leak is not going to help. my 3mm motor took a lil while to start up.

if he has or can get his hands on a commander unit its very easy to check the tps specs which is what i would recommend. and the tip for not stripping the tps screws is to just take the throttle body itself off and loosen them up.

i do not disagree that the tps is the problem i just dont want him to have the same scenario i had. i hope he has a quick fix with the tps calibration. but please before you adjust it just probe the connector and write down your specs so you can go back.

-Lance

he moved it to a different TB.

and a vacuum leak would mean more air passed the throttle plates...increasing idle rpm. not stalling the car.

^ good one didn't see that with the tb. your absolutely right! another thing i thought of. did you change map sensors? i did not switch my settings (i forget which option) for the map sensor and it would cause the car to die if i let off the throttle.

the simplest thing at this point would be to adjust your tps and have the air screw closed at first. its normal to turn it a little bit afterward to clear up problems.

from this point forward i will not contribute misleading information :(

Gene, i told you its the TPS!

If you moved the TPS from one TB to another, the settings are off and you have to adjust it again.

I was in the same situation as you, thats why i know.