Hi there all....Needing alittle help here (thing is driving me crazy). I recently did a small overhaul on my 95 cobra, with the addition of a FMS B-303 camshaft. Everything went very well, until I tired starting it. The issue here is....If a go outside first thing in the morning, the car starts right up and idles beautiful. I can even drive the car, and it drives awesome (no miss, hesitation, etc...). But as soon as I kill the car, then try and start it back up again..., the car will NOT hold an idle !. As soon as I lift my foot, it stumbles and dies. I have replaced items new below... I even purchased a BAMA 4 bank chip, thinking it would stabilize the idle, which it did not. But the chip really did help out performance.
The only thing I have NOT done is "check for codes". I am planning on doing that this weekend.
New items replaced
both 02 sensors
new plugs and wires
New dizzy, cap, etc...
New cold air intake
new air filter
New fuel pump
.....Timing is at 10*
I did remove the EGR with a delete plate. and also remove the motor for the gas fumes canister.
Also what’s funny is when I hook up the code reader and start running the self test and pulling codes, The engine holds a steady idle But if I turn the unit off the car dies. Or if I leave it for a couple of minutes and the car will eventually die
That sensor reads coolent temp for the cold engine to warm transition, like a choke for efi. It tells the computer engine temp for timing control too. Not sure why the reader makes it run better, there is a chart in the checklist that gives values for the sensor, temp=resistance.
Your code reader, when running the KOER self-test, will rev up the engine a bit. So it's not at all unusual for it to run better during the test as you're describing a problem at-idle. Sounds to me like your open-loop warm-engine settings (low-rpm fuel-related) in the Bama tune need some adjustment.
When you start the car cold, the computer is running on open-loop settings, and the fuel mixture is enriched due to the cold engine temperature.
As the car warms, it transitions into closed-loop settings, where the O2 sensors determine how much fuel to provide.
Everything's good up to this point.
When you stop and re-start the car, it goes back to open-loop settings, but since it's warmer, the fuel mixture isn't going to be enriched, and if those base settings are off (open loop, warm engine fuel settings) the car may not run well. There's also a fuel "startup table" that adds a bit more fuel (depending on engine temperature) at startup, it may be adding a bit too much or too little.
If you manage to keep it running for a while (about a minute) the car should go back into open loop, and should start running properly again. If that's the case, this could be tuned out.
Bama's 'tunes for life' right? I'd get in contact with them, explain the problem, and they may want a data-log but should be able to adjust this for you.
A faulty computer is very unlikely to be the problem. A bad ECT sensor could cause you to be getting too much or too little fuel for the given conditions - you definitely want to correct that before proceeding if the sensor is in doubt at all.
I suspect the problem is the same before and after the Bama tune because they probably didn't adjust those values at all.