Misfiring and Hesitating

[Malo Hombre]

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.

[Wayne's World]

Replace your VANOS seals. Beisan Systems.

[TwinsPoppa]

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.

[Malo Hombre]

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?

[X5 Meister]

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.

[X5 Meister]

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

Originally Posted by Wayne's World

Replace your VANOS seals. Beisan Systems.

[Philly X5]

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...

[Wayne's World]

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.

[Wayne's World]

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.