stevebez

So got this 'issue' when I come off the throttle and decelerate engine drag at low rpm (~2krpm) I get a popping / light backfire in the exhaust (no doubt excess fuel burning off in the exhaust).

So two things - I don't think I am doing damage given its not backfiring through the intake but I am concerned I am running too rich - so as I come off throttle the unburnt fuel is able to be ignited in the exhaust I don't think I am leaking in throttle closed position although don't think I can rule it out.

So is it tune, Injectors, O2 sensors, Kleeman Cams, other?

Sounds rather nice tbh - but running too rich is not ideal and could wash the cylinders / foul up the plugs - which were not pretty at the last service.

Any thoughts or ideas? Leave it or have it seen to?

Car is an '06 pretty much a full house of mods. On exhaust no front cats but do have secondaries, Kleeman header into to stock resonator, Kleeman Cams.

Thanks.

C_Note

Mine does it sometimes when it’s cool/cold out. It’s done it since I got the car. The only “mod” I have is a pulley. What was the temp when it happened to you?

Better too rich than too lean imo…

stevebez

Around 60 deg F/ 15 C but its somewhat temp independent for me.

Agree rich is better but my plugs at last service were pretty messed up. Car runs very strong though…

UncleBenz55

I noticed mine did that when one of my fuel pumps was broken. After replacing the fuel pump system I have never had this occur again.

stevebez

That's odd ... assuming a broken fuel pump would make you run leaner I guess or have lower fuel line pressure...

C_Note

Mine did it in the 30-40s when I had the extra resonator. After I removed the middle res it doesn’t do it nearly as much

Solo wing

My ML63 used to pop / backfire alot when I lift my foot. I had a low fuel pressure error code so I replaced the fuel pump and it does not pop anymore.
I think when the fuel pressure was low, the injectors timing was increased to compensate, however, this is not as accurate as having specified fuel pressure so it results in a rich situation.

UncleBenz55

I'd defenitley check the fuel pressure. It should be 5.5bar on engine start up and drop to 5.3bar after a few seconds. Not sure if Mercedes has the pumps on storage over there. I bought the last pump in Germany yesterday with Part number A211 470 64 94.