backfire on startup

[JimG]

I have done a quick search and found no directly associated info, so here I am.
On the occasion, my car will backfire on startup. I thinks its through the intake as the last two events caused my idle to increase.
A couple of weeks ago it happened, and the idle jumped up to 1100-1200 rpm. I have spoken to my local mech/builder, and I am scheduled to visit him, however yesterday it backfired again prior to starting and now the idle is an unmanageable 2200 rpm.
So now i have two, no, three problems to solve.
1. backfire at the first turn of the key (doesn't happen every start, though??)
2. idle at 2200 rpm. (SM shows .42 TPS while at this idle rpm)
3. drive to my mechanic with the idle so high (lot of traffic... many red lights, 40 minute drive, etc)
It was mentioned that a gasket might have been pushed out when the backfire occurred.

Any other thoughts or ideas?
Many thanks
Jim

 

[turbofabricator]

Sounds like a cam sensor timing issue. Or possibly an ignition module going south. Re-do the cam sensor install, check the crank sensor for contact, too. Have the ignition module checked with a Caspers tool. (find someone local that has one to borrow/rent.)

 

[JimG]

thanks for the quick reply, Ken.
all parts listed were new last year and only have 1,000 or so kms.
any way to lower the idle so I can drive it comfortably over to Dave's?
Jim

 

[JimG]

update

For those who are interested:

1. The backfire was likely caused by the cam sensor being slightly out of adjustment.

2. the high idle was created by the backfire through the intake bending the throttle plate, making it unable to close completely. The throttle body originally was sent out for porting and reconditioning at Steve Monroe's shop. I guess the "knife edged" blade was a little to fragile and took the impact of the backfire.

So, once the TB gets repaired, the crank sensor will be checked and the cam sensor reset, we should be good to go.

Again, many thanks to all assistance offerred.
Jim

 

[stevemon]

update

For those who are interested:

1. The backfire was likely caused by the cam sensor being slightly out of adjustment.

2. the high idle was created by the backfire through the intake bending the throttle plate, making it unable to close completely. The throttle body originally was sent out for porting and reconditioning at Steve Monroe's shop. I guess the "knife edged" blade was a little to fragile and took the impact of the backfire.

So, once the TB gets repaired, the crank sensor will be checked and the cam sensor reset, we should be good to go.

Again, many thanks to all assistance offerred.
Jim

TO add to the info Jim posted, the throttle plate was made of .062" thick 6061-T6 aircraft grade aluminum. Here's a pic of the plate. BTW the halfshaft held up fine.