3.4 DOHC pops while cranking but runs fine

[Series8217]

My 1993 3.4 DOHC pops while cranking (sounds like a backfire out the intake) but once it starts it runs fine.

Brand new injectors.

Ideas?

[FieroWanaBe1]

Are both crank sensors reading correctly?

[Series8217]

Are both crank sensors reading correctly?

There is only one crank sensor. It's a '93.

The motor runs fine with no error codes. I would suspect if there was a problem with the crank sensor I wouldn't have a running motor at all.

[FieroWanaBe1]

Ok. My bad, I thought all years had 7x and 24x, with the addition of the 2x can sensor in the later years.
To me it sounds like timing is off only during cranking.but what could cause that?

[ericjon262]

Are both crank sensors reading correctly?

There is only one crank sensor. It's a '93.

The motor runs fine with no error codes. I would suspect if there was a problem with the crank sensor I wouldn't have a running motor at all.

Doesn't the ICM handle spark while cranking? could be the ICM on the way out.

[Shaun41178(2)]

coil pack? waste spark not working correctly?

[The Dark Side of Will]

My 1993 3.4 DOHC pops while cranking (sounds like a backfire out the intake) but once it starts it runs fine.

Brand new injectors.

Ideas?

This is typically a sign of leaking intake valve seats.

Also, have you checked the fuel rail pressure leak down? If you have a leaking injector (it can happen to brand new ones, especially "offshore" units) dribbling fuel into the port, all the time, it might have some problems.

[Series8217]

Doesn't the ICM handle spark while cranking? could be the ICM on the way out.

Yes! I forgot I replaced the ICM at the same time as the injectors. That could be it. I have a few spare ones I can try.

Also, have you checked the fuel rail pressure leak down?

Yes... but I'll check it again as it has been awhile.

[Series8217]

Replaced ICM and coils; no change...