Backfiring issues

PHillary · PHillary's Garage

Can anyone give me any clues as to why my car may be backfiring through the muffler good constant sound from car its just when I rev it pas 4000rpms or when I'm in traffic making moves I sometimes hear a few small little pops out of the exhaust. Can this be vacume leaks? any suggestions!

Slam · 07-16-2008, 08:38 AM

Vac leaks? Our 924 does this but I've got the timing way advanced. 944 timing can't be messed with much.

PHillary · PHillary's Garage

I added the MSD iginition ket from Lindsey racing and that is pretty mush it added my own 3" exhaust cat back, throttle cam and new injectors and injector harness from lindsey but I just don't know. Some other small mods but not nothing to fancy added some cool blue high temp fuel lines from rennbay. Just don't know!

PHillary · PHillary's Garage

How does your 924 run? do you daily drive it? I guess what I am asking is it a lot to worry about or I just need to calm down and play a game of hit and miss?

Slam · 07-16-2008, 10:50 AM

I wouldn't worry too much about crackling and popping out the tailpipe. When I blew the muffler on my 944 it sounded like and Indy car! Does yours act up on throttle over-run? Decel? If it does it while you're accelerating with your foot down, I'd wonder. I've never used the MSD but as I understand it, the unit provides more than one spark per cycle, yes? That could be doing it. I'd also go looking for vac leaks. Easy fixes and cures so many problems.

The 924 runs fine as a daily driver. In fact, I'm looking for one for myself (my wife drives the auto) because it's such a fun car. Completely different animal to the 944, though.

PHillary · PHillary's Garage

I will have my Mechanic try checking again for leaks He thinks it's an faulty air flow meter as sometimes the car surges at 1/8-1/4 of throttle being opened. Don't know if this related. I just don't want to buy a new meter for 500-600 bucks and that's not the problem. Will try looking into my haynes manual again. If you guys have any places to start looking or words of wisdom please, please, please pass them along.

PXJ800 · 07-16-2008, 11:49 AM

Just chiming in to say I have MSD and have some backfiring as well. Usually it comes when I am engine braking and hit 2800 down to about 2400, then it stops. It is more of a series of rumbles/crackles than one pop. Occasionally when I am pushing the car a little harder than normal I get a pop in between shifts, usually going up to 3rd. There's no loss of power or irregularity along with it, though.

I was thinking it's just cause my cat's blown, because my car is very loud on top of having that rumble/pop, but I guess I'll be double-checking for vacuum leaks this weekend.