backfire?

[92sho16]

When im driving along an have the need to downshift sometimes when im going down in rpms a backfire sort of sound is emitted from the exhaust. Does anyone know what causes this?

 

[Slo-Sho]

Has the timing belt ever been replaced? Is the belt set at the proper tension?

 

[Ace]

do you have the stock cats on it or an aftermarket y-pipe?

 

[Mr Anonymous]

Backfiring is usually indicative of a timing problem (usually the belt has slipped a cog), or mis-routed plug wires. Have you had any work done to your car recently?

 

[92sho16]

timing belt has been replaced but im not sure when, i have a ss catted y pipe, dynomax catback. Not sure about the tension on the belt. Wires are routed right because the car isnt down on power. The wires do need to be replaced however because i dont know when they were put on the car.

 

[Mr Anonymous]

Wires are routed right because the car isnt down on power.

Um, that doesn't mean anything. I've seen SHO's running on anywhere from 3 to 5 cylinders that still seemed to be plenty powerful. Check the routing. It will take 2 minutes or less. If the plugs are indeed routed correctly, then your next step is going to be to remove the upper timing belt cover, and verify the timing between the cams and the crank.

 

[92sho16]

Um, that doesn't mean anything. I've seen SHO's running on anywhere from 3 to 5 cylinders that still seemed to be plenty powerful. Check the routing. It will take 2 minutes or less. If the plugs are indeed routed correctly, then your next step is going to be to remove the upper timing belt cover, and verify the timing between the cams and the crank.

I guess ill have to check the both of those asap. Thank you for your help.

 

[SHOslyter485]

Well, I see that you have a catted y-pipe and an aftermarket catback.. I've noticed on my catless y-pipe, under hard acceleration or downshifting, the exhaust would pop a bit, but nothing obnoxious or loud.. but I have stock catback.

 

[MichaelH]

How old are the plugs? I'm wondering if it could be the condition of the plugs. I have a backfire occasionally. Not often, and only one at a time. My MTX has the MidwestSHO Y pipe and the rest of the exhaust is stock. However, I run plugs one range cooler because of the NOS, so I attribute it to the plugs not being the ideal type.

Since the plugs fire on every stroke, it could be if a plug misfires on the power stroke, it could fire on the exhaust stroke and cause the backfire. Or, maybe that couldn't happen and it's just wishful thinking.