exhaust goes "grumble grumble pop!"

[hahaitzskippy]

1985 318i m10
when i let off the gas and slightly depress the gas... the exhaust pops and grumbles.

am i running rich? should i be concerned?

im still getting about 30 MPG mix highway and street...

[EatsHondas]

Does the noise sound mechanical, like the actual exhaust is the problem? Or can you tell if it's noise from the motor? If you're still getting those nice fat mpg numbers, I'd seriously doubt you're running rich.

[hahaitzskippy]

it exactly sounds as if teh gas is igniting in teh exhaust system.

it is defintely NOT the motor.... i was hoping it was running a little rich... that would help me pass smog...

not a problem... yet? just wanted to share to see if anyone had any input or preventative measures.

[E30_Pare]

My car has always done that. When I rev to about 4k. "Snap, crackle, pop Pop POP". Same at redline. Exhaust is toast though.

[E30_Pare]

Oh & car runs excellent about the same gas mileage.

[EatsHondas]

Cars can backfire from being too lean as well as being too rich. If it were mine, I'd pull the spark plugs and see what they look like. Wet or a sooty black would indicate rich while a white scorched look would suggest lean.

The Bentley manual lists 12 possible causes of rough running/backfiring, but the best place to start (ie not spending any money) would be to look/listen for intake leaks. If you google around, you should be able to score yourself a free download for the manual.

Exhaust is toast though.

Another easy thing to check. Dive under the car and take a look.

[Hooffenstein HD]

Mine does the same thing but M20B23. Everytime I let off the gas, it crackles and pops. I figure it's probably running rich.

Also has a funny idle issue though. On start up, it will idle at 1700RPM and gradually drop down to 1,000RPM.