# Car Backfiring **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [February 29, 2008, 11:52pm UTC](https://community.cartalk.com/t/car-backfiring/11290 "2008-02-29T23:52:47Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![1weeks2go](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/1weeks2go/32/696_2.png) [@1weeks2go](https://community.cartalk.com/u/1weeks2go)\ **Post date:** [February 29, 2008, 11:52pm UTC](https://community.cartalk.com/t/car-backfiring/11290/1 "2008-02-29T23:52:47Z")
I have a 1990 pontiac firebird 305 tpi. It is backfiring out the exhaust. I have change the plugs, wires, distributer cap & rotor, added injector cleaner. It has a new remanufactored ecm unit. Im stuck! can anybody help? ~ Kurt ~ ---
**Author:** ![willey](https://avatars.discourse-cdn.com/v4/letter/w/a9adbd/32.png) [@willey](https://community.cartalk.com/u/willey)\ **Post date:** [February 29, 2008, 11:57pm UTC](https://community.cartalk.com/t/car-backfiring/11290/2 "2008-02-29T23:57:20Z")
Have you checked the timing? ---
**Author:** ![1weeks2go](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/1weeks2go/32/696_2.png) [@1weeks2go](https://community.cartalk.com/u/1weeks2go)\ **Post date:** [February 29, 2008, 11:58pm UTC](https://community.cartalk.com/t/car-backfiring/11290/3 "2008-02-29T23:58:41Z")
Yes, 6 degrees ---
**Author:** ![1weeks2go](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/1weeks2go/32/696_2.png) [@1weeks2go](https://community.cartalk.com/u/1weeks2go)\ **Post date:** [March 1, 2008, 12:01am UTC](https://community.cartalk.com/t/car-backfiring/11290/4 "2008-03-01T00:01:32Z")
yes, 6 degrees ---
**Author:** ![winarth](https://avatars.discourse-cdn.com/v4/letter/w/b5a626/32.png) [@winarth](https://community.cartalk.com/u/winarth)\ **Post date:** [March 1, 2008, 2:13am UTC](https://community.cartalk.com/t/car-backfiring/11290/5 "2008-03-01T02:13:48Z")
Are you sure the plug wires didn’t get crossed somewhere? ---
**Author:** ![MG-McAnick](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mg-mcanick/32/188_2.png) [@MG-McAnick](https://community.cartalk.com/u/MG-McAnick)\ **Post date:** [March 1, 2008, 2:56am UTC](https://community.cartalk.com/t/car-backfiring/11290/6 "2008-03-01T02:56:05Z")
Did it run right before you worked on it? ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [March 1, 2008, 3:43am UTC](https://community.cartalk.com/t/car-backfiring/11290/7 "2008-03-01T03:43:20Z")
Did you check the ignition timing with the test connector grounded though? Backfiring out the exhaust may mean the timing is retarded too much. ---
**Author:** ![willey](https://avatars.discourse-cdn.com/v4/letter/w/a9adbd/32.png) [@willey](https://community.cartalk.com/u/willey)\ **Post date:** [March 1, 2008, 1:24pm UTC](https://community.cartalk.com/t/car-backfiring/11290/8 "2008-03-01T13:24:01Z")
Good point. I looked up the procedure for putting it in base timing and the procedures are different for a engine with a carb and a fuel injected engine. ---
**Author:** ![1weeks2go](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/1weeks2go/32/696_2.png) [@1weeks2go](https://community.cartalk.com/u/1weeks2go)\ **Post date:** [March 1, 2008, 2:55pm UTC](https://community.cartalk.com/t/car-backfiring/11290/9 "2008-03-01T14:55:19Z")
Yes, I did check the timing by disconnecting the timing advance wire. I was reading in the chiltons hand book about the emissions air pump diverter and valve. what do you think about that? could that be a possability?