Timing Chain Issue/ Misfire P0306

[RomanKnight]

I have a 2009 335i Coupe E92 and while driving I got a Check Engine. I took it to a mechanic and he said it was a timing belt issue and that the timing belt was slipping. He wanted to replace for $ 6K. he said not to drive it because it could damage the car. I asked for the detailed diagnosis report. I looked it over and the mechanic that actually worked on my car, reported a code of " misfire 6 cylinder ". P0306 code. I replaced the ignition coil on cylinder 6 and the code vanished. It was running fine for a while and then started to idle rough. Does anyone have experience with this issue ? The shop manager said, he made the timing belt slipping diagnosis because of the sound the engine was making and not any codes. Could he be right ?

[RepairGuy]

There is no belt besides the main drive belt. It is a chain driven engine and not a common issue unless you are really bad with oil change intervals etc. So I would say that is unlikely the issue. I think you need to do a full tune up, not just the one coil. Use a quality set of NGK iridium plugs, and put a set of new coils on. Once one goes out, they generally start dropping like flies. Again, good quality like NGK or OEM replacements. A duralast coil from autozone is a big no no for any BMW. They wont work or last long if they do. Another commonly neglected service that has a lot to do with a good idle is to simply clean the throttle blade of carbon build up. Generally you have to do a reset of the computer to re-lean idle after servicing it. But the idea here is that over time, the blade gets gummed up and allows less air through which makes for poor engine performance, poor idle, loss of fuel economy, throttle response, etc. This is especially common on a turbocharged engine. Those are my suggestions. Full tune up with high quality parts and a throttle service.

[White94RX]

Find a new shop. They don't know crap about BMW's. They don't have timing belts. They have a chain. It can't slip.

The first step in diagnosing it is to scan for fault codes. Is the check engine light on?

[jclausen]

The shop is so full of shit they need to be out of business

[JDStrickland]

I have a 2009 335i Coupe E92 and while driving I got a Check Engine. I took it to a mechanic and he said it was a timing belt issue and that the timing belt was slipping. He wanted to replace for $ 6K. he said not to drive it because it could damage the car. I asked for the detailed diagnosis report. I looked it over and the mechanic that actually worked on my car, reported a code of " misfire 6 cylinder ". P0306 code. I replaced the ignition coil on cylinder 6 and the code vanished. It was running fine for a while and then started to idle rough. Does anyone have experience with this issue ? The shop manager said, he made the timing belt slipping diagnosis because of the sound the engine was making and not any codes. Could he be right ?

I'm sorry, but what you need is a new mechanic. If the timing belt slipped, it would be a global catastrophe, not a single cylinder misfire. The Timing CHAIN would not slip in a manner that made one cylinder fail, it would affect all cylinders.

[RepairGuy]

The shop is so full of shit they need to be out of business

I wouldn't go that far.. I am a technician and in defense of that guy.. we don't know what condition the OP's car is in. It may have a misfire or two, but it may have nasty internal engine noises too that the tech feels is from the timing area. I don't think it's the misfire cause, but it may be an issue that the tech suggests needs fixed. Things get lost in translation. Maybe they suggested not putting any money into the car and didn't touch it, hence the OP getting his own coil. I see it all the time. A guy buys a falling apart BMW on it's last legs, but he just had to have it. Never saw oil changes because the prior owner couldn't get the jiffy lube $25 special they got on their corolla. Thing is beautiful but has tons of issues. This might be the OP's car. Much more difficult and expensive than the average car to repair. So most people that bring their Bimmer in turn down the recommendations that it needs. That's the car that buyers end up with. Oil coming out of every place possible, trans leaks, loose control arms and blown struts. It's seriously 80%+ of this era of BMW I see on a daily basis.

[relative4]

Well said sir.

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