Rough Idle, Rotten egg smell from exhaust

[insightbrewery]

Hey guys, I am working on a friend's '95 318i M42 and need some help. I just did a fair amount of work and now it has a rough idle, no power, and a rotten egg smell from the exhaust after a few minutes running. Car was running OK before a fair bit of work. Some background:

The car sat for a year until they started it up - it started pissing fuel from the fuel filter hose bits so they towed it for me to look at. I replaced the fuel filter and its hose bits, and then a leak sprang from the hose coming from the pump (visible at the bottom of the tank where it attaches to the hard lines running under the car). So I ordered the hose kit (the blue plastic ones with crimped rubber hose at the ends), dropped the tank, and replaced all those lines, including the EVAP ones. Also noticed the fuel pump had a cracked nipple so replaced that with a brand-new OEM VDO.

Next up, I did a full tune-up: OEM NGK plugs, wires, air filter, cabin air filter, oil change. Also replaced PCV valve and hose, plenum/PCV adapter gaskets, one IAC hose that had splits in it, and VC gasket that was leaking. Tried to start it up - it fired up, but would die quickly: I forgot to hook the new IAC hose to the intake boot. Fixed that, fired it up again - the tach held steady at 600 RPM or so, but engine was really rough, shaking the whole car. Giving it some gas and holding the pedal steady (constant position) would cause the RPMs to rise, but choppily. No change after it warmed up, but the exhaust started smelling like rotten eggs.

I turned it off, soaked the IAC valve (which had a light coating of carbon) in Chem-Dip, reinstalled it, and did a smoke test to find any vacuum leaks. No vacuum leaks, I stopped when it started pouring smoke out the air filter housing as the intake manifold filled up. Started it up, same behavior. I disconnected the TPS and MAF, one at a time while the engine was running. TPS, it dropped RPMS, then caught up and idled higher than it was (above 600 RPM, that is). MAF, it didn't drop, but idled higher. Both times, still rough as all hell. I turned it off, kmdid the gas pedal five times and read the code: just 1215 because I unplugged the MAF. I pulled the battery for ten minutes, then made sure the 1215 was gone, started it again and let it run for ten minutes - no codes, but the transmission fault light illuminated.

That's where I left it - I'm stumped if anybody can offer some advice. Thanks!

[DesktopDave]

You hit all the problem areas for me, that's for sure. Rotten egg smells usually make me suspect the catalyst or O2 sensor. A bad coil or two would cause these kinds of problems too, these DMEs tend to develop cold solder joints on the coil drivers, leading to damaged coils.

If it's an E36 (especially if it's been sitting) the cowl drain 'elephant trunk' tends to plug up with dirt & leaf debris...then the DME compartment will be flooded with heavy rain, car wash, etc..

Did you run a fuel pressure test/compression test, etc.?

I know it's a little late, but the #1 mod on these cars is to replace the expensive OEM coils & plug wires with a COP plate & M52 coils There's a kit developed by Rob_D on sale here somewhere IIRC.

[insightbrewery]

LOL figured out the problem...with the long plug wires as snakey as they are, I switched #2 and #3. Car runs like a top now, although it has myriad other problems from neglect.

Thanks for the COP recommendation, next time I'm working on one I'll suggest that!

You hit all the problem areas for me, that's for sure. Rotten egg smells usually make me suspect the catalyst or O2 sensor. A bad coil or two would cause these kinds of problems too, these DMEs tend to develop cold solder joints on the coil drivers, leading to damaged coils.

If it's an E36 (especially if it's been sitting) the cowl drain 'elephant trunk' tends to plug up with dirt & leaf debris...then the DME compartment will be flooded with heavy rain, car wash, etc..

Did you run a fuel pressure test/compression test, etc.?

I know it's a little late, but the #1 mod on these cars is to replace the expensive OEM coils & plug wires with a COP plate & M52 coils There's a kit developed by Rob_D on sale here somewhere IIRC.