Sounds Like a Harley...

[nirvana19]

I finally replaced the vacuum hose to the FPR and after I started the car and it seemed to be running as usual. The idle was a little lower but the car seemed to be running as well as usual. Came back 20 minutes later to go drive somewhere and it started immediately and sounded like a Harley. Exhaust was clearly louder than usual with a pronounced popping..drove around the block once and when I put it in park the CHECK ENGINE light came on. Again, did absolutely nothing from when I shut the car down after changing the FPR (and it was fine) to when the problem occurred. Visually inspected everything and nothing looked unusual, anyone have any idea what the hell is goin on?

Oh, and duh the code was 1222 (lambda control 1). I think that's either related to o2 or vacuum leaks...going to check to see if I knocked a vacuum hose loose somewhere when I was feeling around the intake manifold.

[JD525IA]

I finally replaced the vacuum hose to the FPR and after I started the car and it seemed to be running as usual. The idle was a little lower but the car seemed to be running as well as usual. Came back 20 minutes later to go drive somewhere and it started immediately and sounded like a Harley. Exhaust was clearly louder than usual with a pronounced popping..drove around the block once and when I put it in park the CHECK ENGINE light came on. Again, did absolutely nothing from when I shut the car down after changing the FPR (and it was fine) to when the problem occurred. Visually inspected everything and nothing looked unusual, anyone have any idea what the hell is goin on?

Oh, and duh the code was 1222 (lambda control 1). I think that's either related to o2 or vacuum leaks...going to check to see if I knocked a vacuum hose loose somewhere when I was feeling around the intake manifold.

Tell you what, it sounds like the ECU made some adjustments after the car was running a while. I would do a Shogun reset (disconnect battery for a while) and then drive it again. Could be that once the catalytic converter got warm the output went out of range on the O2 sensor. The backfiring could also damage the cat, so be careful.

JD

[nirvana19]

Did a shogun reset, but it didn't clear the problem, still backfiring (pop pop pop pop). Could the properly functioning FPR somehow stressed one of the injectors and busted a seal? I actually have six refurbs waiting to be installed so I'll try to swap them tomorrow. Checked the FPR vacuum hose, brake booster, and that other one near the FPR in the intake manifold. Nothing seems amiss, am I missing something?

[e34.535i.sport]

Did a shogun reset, but it didn't clear the problem, still backfiring (pop pop pop pop). Could the properly functioning FPR somehow stressed one of the injectors and busted a seal? I actually have six refurbs waiting to be installed so I'll try to swap them tomorrow. Checked the FPR vacuum hose, brake booster, and that other one near the FPR in the intake manifold. Nothing seems amiss, am I missing something?

If you can distinctly hear the pop and suspect an injector then use the screwdriver to your ear trick to see if you can locate the pop and go from there... Keep us informed, hope you can get to the bottom of it.

[tim eh?]

i dunno about a bimmer, but if this were my old van i would say exhaust manifold, and that's without the o2 sensor clue.

[nirvana19]

Did the fuel injectors, no change in the backfiring. It's coming from either cylinder 5 or 6 and can be clearly heard in the engine bay, so I think the exhaust manifold gasket has completely blown. They found that one was leaking long ago but it seems to have become a severe exhaust leak. One of the vacuum hoses (that connects to the intake boot) is missing but removing the oil cap or pulling out the dipstick causes a significant change in idle, so the vacuum leak isn't THAT bad. Will take it into an exhaust place and report back.

Current theory is that the gasket(s) is blown so 02 sensor is reading that the engine is running lean and that's what's giving me the lambda 1 code (and presumably dumping more fuel into the engine so it's running rich). I don't think it's actually backfiring, just loud because of the exhaust leak.

[tim eh?]

I don't think it's actually backfiring, just loud because of the exhaust leak.

that's what made me guess EM - you are probably correct, it's not backfiring.

loud as %$#@ isn't it.