Mechanics

BACK FIRE AND CYLINDER MISFIRE

2007 Dodge Ram • 90,000 miles

2007 hemi pick up. I keep having a back fire. One tech said it's a miss fire on cylinder 6&7. I changed all 16 plugs. Still problem. Changed coils on 6, 7&8. Changed the cam or crank sensor (the one right below the alternator). Still having problems. No codes are being thrown on the computer. Help please
Avatar
Schirico
December 30, 2011.




Is the backfire intake or exhaust?

Tiny
Fixitmr
Dec 30, 2011.
Exhaust

Tiny
Schirico
Dec 31, 2011.
Backfire thru exhaust confirms misfire. So how did old plugs look? Especially 6-7. And does your motor have MDS?

Tiny
Fixitmr
Dec 31, 2011.
You could try switching injectors on 6-7 with nextdoor cylinders and see if problem moves with them?

Tiny
Fixitmr
Dec 31, 2011.
The old plugs looked good. Don't know what MDS means. Do injectors get bad or do the clog up.
AD

Tiny
Schirico
Dec 31, 2011.
MDS is gas saving 4cyl operation when cruisin. Injectors do both.

Tiny
Fixitmr
Jan 1, 2012.
Yes. And I notice the backfire when I let off the gas pedal

Tiny
Schirico
Jan 1, 2012.
I would say MDS takes this diagnosis beyond do it yourself. VVT adds extra complications to any attemp to guess at fix. You will have to take it in to get diagnosed with the right equipment and procedures.

Tiny
Fixitmr
Jan 2, 2012.

AD