Well heres the deal, the car is a mildly modified 350 TBI, the mods are in the sig, but also the engine has the crappy 305 TBI heads on it, these will be swapped out withing the next few weeks, i just bought a set of L98 Aluminum vette heads and they are getting ported, and redone as we speak. But anyways, here it the issue, I cannot get the car to stop smoking. Or to run right on startup. The car, when cold, (not necessarily the weather), but the engine is cold will not run good at all, it starts up fine, but will want to stall out if i do not give it a little gas, but if i try to gas it too much the car will die and stall. I cant drive it, because once the gas is pressed down too far it wants to stall out, and also im having a big problem with smoking, it smokes 9 times out of 10 on startup, its fuel, i know because i can smell it and it will burn your eyes. But it will be fine if the car is going downt he highway, or just idleing, however once you throttle it more you get the puff of smoke, the car seems to be running incredibly rich. Could this all be a result of me running the 350TBI Holley 670 unit with the 65pph injectors, any possible sensors that might make this occur, anything...? At this point im about lost, the car was running decent last summer, but still not perfect, but now the car seems to be worse, im not sure if im running too much TBI on it, or what. Any help would be greatly appreciated, thanks guys.

 

no one has any ideas or thoughts ? wow, this is getting really frustrating

 

I don't know a whole lot about the ECM and reprogramming or any of that stuff, but I'll make a pass at what it could be.

When your car is first started ("warming up") the ECM is in open loop mode. It pays no attention to the 02 sensor at all. It has set parameters that it follows no matter what. One of those parameters is to run a little rich.

You have 65pph injectors. The factory injectors are (IIRC) 44pph. The computer has no way of knowing you changed them, so when it's in Open Loop, it thinks you have 44pph injectors, and treats them as such. Same pulse width, same IAC control, same amount of advance.... etc. etc.

You're now feeding the car A LOT more fuel at start up compared to what the ECM is used to. Until it goes into Closed Loop (which happens either after a certain coolant temp, or timeframe, whichever comes first) it will keep doing that.

Once it goes into Closed Loop, it uses the O2 sensor and sees that it's running really rich, then corrects that by decreasing the pulse width, increasing the IAC... etc. That's why it's fine (or as fine as it can be without programming a new PROM) after it "warms up".

That's just my educated guess (or lack thereof ) so don't take it as gospel. You need to burn a new chip with new parameters.

 

My two cents?

in a word;

CHIP!!

I went from a 305TBI to a 350 Vortech 330 hp engine and mine did the same thing. I put in a Esc module for the cop car, the 65lb injectors, a 350 knock sensor and still ran like poop. If you've already done these things, then you need a 350tbi chip.

Your chip still thinks it's a 305 and with a cold engine, it's still feeding it like it's a 305. Not good. Is it hesitating, a little poping noise from under the hood, gnerally acting wierd? It's that you need a custom chip.

Once you get a custom chip you'll have to mess with the timing again, but the custom chip will help you a lot.

Good luck!