Engine fires before cranking.
 

Sometimes when I turn the key to ignition my engine pops. This seems to happen hot or cold. What is happening is this.

I get in to start the car
put the key in
turn it to ignition (one before CRANK)
a small explosion emits back through the intake manifold.

Makes a pop sound. The microtech says the engine is in a idle state just after this all happens. Seems like some spark plugs are firing at will! Usually when this happens a vacumm cap blows off. I have yet to catch this happening when my foot is on the gas 1/4 while turning the key to ignition.

This has popped 7 times since I installed the microtech.

I wonder if you have leaky injectors? The fuel pump primes when you turn the key to on. Just a theory.

Man has this happened to anyone eles? I don't need this type of stuff to happen to me.

Does anyone know what this is? I too would like to know.

Brandon?

I havent heard of this heppening before, the only reason it would do this is if it is picking up a signal from teh CAS and then would pluse the injectors and the coils,

check you CAS wiring,

No problems here, I did have a problem with my Talon back fireing after i turned it off when I was trying to install a PMS on it once. That was weird enough.

Daniel

It's probably the coils firing - might be getting some sort of surge to the coils that's making them discharge. That could be a tricky one to trace down!

Dale

What about the 12V wire that's "supposed" to supply power to the coil...could it be mixed up with the signal wire?

The wiring checks out. This is on an LT8x unit.

Yes the injectors probably have a small leak, either that or they inject while the motor turns off from the run before.

Dale, I tried moving some of the CAS wires around a little and I reseated the connector at the CAS. Im waiting for this to happen again.


I do notice that my tach kicks just a tiny winsy bit. like it just pulses off of 0 for less that 100th of a second.

I noticed on a haltech when you turn the ignition to on, the coils will fire.. (check this using a timming light)


We where having trouble with the coils so i am not sure that is 100% normal though..


We never got a pop though.. check your injectors.. they may be leaking.

Or they may not be leaking if the ecu injects fuel continually upon engine shut off.

Or maybe the ecu is injecting fuel when I turn the key to ig. Either way, leaking or not, its still not normal unless Microtech says its normal.

Good advise with the timing light though.

my haltech will pop like that sometimes. It definitely sparks the ignition when you give it power b/c I bumped the battery cable to the post and I got a nice little shock in the arm from my leading coils

I kind of dont care about this problem anymore. Its bothersome but whatcha gonna do.

I just open the throttle when I turn the key so that my vacumm caps dont bust off.