Hi,
Heres the problem, My 89 Formula (its a 305 TBI with the 700r4 box) keeps stalling when sitting stopped at the lights with the shifter in D and my foot on the brake. It also stalls when going from D to R or from R to D.

It NEVER did this before last week, when I had a new ignition coil, ignition module, dizzy cap/rotor and new plugs fitted after the original coil/module died. The cars previous owner has had Edelbrock cam and valves professionally fitted along with a Hypertech superchip . However the car ran perfectly right up to me having the ignition parts replaced.

Last night I followed the instructions on this site for adjusting the idle mixture/speed (putting the computer in diagnostic mode, adjusting the idle screw with the IAC disconected ect ) and the car is now sitting totally steady and sweet at 450ish rpm. But still stalls when sitting at the lights for over 1 min or sometimes when going from D to R.

Ive got an Edelbrock air filter installed, inplace of the factory cleaner/snorkel. On the TBI body, just to the left of the idle adjustemnet screw, there is a small pipe (looks like an air bypass or something) going straight into the throttle body. This is currently plugged. Should this be open (if so where did it go) or plugged up?

Should I repeat last nights steps regarding the idle adjustment but with this small pipe unplugged.....will this cure my stalling problems? My Rev counter also died the same time as the coil/ign module packed up, so I have no exact way of knowing the rpm

Im in Scotland in the UK........so you guys are the best chance Ive got of fixing my car. I pretty much rebuilt my last Formula due to all teh info on this site!! Hope someone can help!

Cheers, Alastair.

 

That small pipe is probably the vacuum tube that went to the THERMAC system that was on the original TBI air assembly. Definetly keep that plugged (otherwise you've got a terrible vacuum leak).

As for the IAC, try opening it up more. I'm not sure what is a good idle, but my basically stock 305 TBI idles at 550rpm.

 

An idle speed of 450 is too low. Should be like 575 or so. Possibly you may have a faulty IAC if it really does idle that low. It may also explain the stall when shifting into gear. The IAC should open slightly when shifting to help compensate for the load.

 

Well my pc died the death......sorry its taken so long to reply to this! thanks for the ideas.....I took out the iac valve and the shaft had seperated itself from the valves body??!! Went over the whole TBI unit with Carb cleaner and screwed the shaft back into the IAC valve......adjusted the idle and it now idles in P or N at around 850 and sits in D, OD or R at around 600rpm roughly....hasnt stalled since so looks like it might be sorted now!

there is a noise comming from the engine under acceleration, sounds like its "pinking" so Im going to have a shot a adjusting the timing tomorrow if I can find the timing light lol!

 

My car would do this everyonce in a while, but would only do it when i shifted into reverse. I had tuned the car up completely and didn't make a difference. I ended up replacing the distibuter and that took care of it. My distributer was corroded(sp?)up and nasty. My car idles smoother now too. Hope this helps.

 

Hey Black T top, where did you read the tune up procedures at???? I am looking for it myself, Thanks, Tom