Misfiring and Hesitating
 

Thanks to all for the invaluable help of this forum! I have a 2001 3.0, 120k miles, that is hesitating and misfiring. Gas mileage has gone out the window and I'm worried that I have a major problem.

This started after taking it in for an alignment. The mechanic pulled codes and gave me a laundry list of items that needed repaired: Air boot, valve cover gasket, no coolant in radiator and cap missing, exhaust cam sensor, thermostat, and air filter.

First things first, I replaced the radiator cap and filled it with coolant. Then I replaced the airboot and filter. After this, it started to hesitate periodically at low speeds. I read a forum post that suggested cleaning the MAF with carb cleaner, so I gave it a shot. BAD idea! It must have left a residue on the MAF because it would barley run until I found some MAF cleaner at the parts store. At this time I also noticed, at idle, a loud pinging noise like something physically hitting the inside of the case near the adjuster unit.

Meanwhile, my exhaust cam sensor came in and I replaced it. Still no luck, so I took it back to the mechanic. He thought the pinging was a misfire, probably caused by oil in the spark plugs. I pulled the covers and coils. No oil, but I replaced the plugs anyway while I was there.

Next, I changed the fuel filter. Still nothing. With the engine at idle, running rough, I decided to pull of the wire going to the MAF. Low and behold, it smoothed out and ran like a champ! I took it for a test drive and everything was great except that is shifts hard with the sensor unplugged. So, I ordered a MAF from Ebay and hooked it up. Still no luck! ARGH!!!!

I took it to another mechanic. I discovered the first one had overcharged me on the original alignment and he got pissed when I called him on it. The new guy thinks there [FONT='Verdana','sans-serif']IS[/FONT] something physical rattling around in the case, maybe having to do with the timing chain. He wants to charge me $600 to tear it down and find out what is going on.

Any ideas or opinions? I'm not entirely sure I trust that the new mechanic knows what he is talking about. This leaves me with the dealer who want $140 just to look at it.

Replace your VANOS seals. Beisan Systems.

I vote pay the $140 and find out what they say rather than waste more money and time unnecessarily. Those guys SHOULD know what they're doing.

I still can't believe your X still ran w/o coolant. I would have thought it would have overheated and stopped running.

Ya Poppa, I was almost too embarassed to include the info about the coolant. But, it NEVER ran even slightly hot. I also thought that maybe new coolant in a previously dry system throwing a thermostat code could have broken somethinig loose, causing my current problem... I know, it's a stretch.

Does anyone know if bad VANOS seals would cause misfires? AND could the sound of misfiring be mistaken for something physical rattling around inside the case?

That could be the best $140 you've ever spent if you don't already have an indy that you like. Contact a local BMW CCA chapter for recommendations on quality indy's in your area.

Wayne- thanks for the link. Some outstanding write-ups on it. Wow!

Hey,
maybe a crazy idea but did you check Idle Control Valve & Idle Adjuster unit?
I had a problem with my Idle Adjuster Unit on my old e46 and the rubber seal on it was rotted/bad & allowed air into the intake causing all kind of error codes...

No prob. I'm on the cusp of doing it to my X. But basically from the testimonials to the write-up, it all makes sense. Esp. since Malo was having exhaust camshaft sensor errors. If it doesn't fix the source of the problem, it definitely is a worthy repair. I currently am experiencing no problems with my X but will do it anyway. Gives me a chance to replace the valve cover gasket. My X (M54) has 87K on it and my E39 with the M52TU motor, the valve cover gasket was like hard plastic instead of rubbery that it just broke into a million pieces when I tried to pry it off the cover. I'm sure it needs replacing in mine.

Malo - The rattling could actually be your VANOS pistons. In the VANOS Seal repair, you are replacing the o-rings and rubber rings that have hardened and are basically like plastic. Imagine the rings around your pistons shrinking and leaving a sizeable gap between itself and the cylinder wall. I'm sure you'll hear some sort of noise.