[phatchuck]

I just purchased an N55 with 94K on it. It's been throwing a 'drive train malfunction' code and when it's off the SES light is on. Three weeks ago the dealer had it for a week and said they put some 'chemicals' in the DI ports to get rid of some of the carbon buildup.

Two weeks later I get the same error again with the SES light on. I call my real mechanic and he recommends a Techron fuel injector cleaner cycle. Added it to a nearly full tank of 91 octane fuel. When that was gone, added another bottle to a nearly empty tank with Sunoco 93. I also have it an Italian tuneup - driving for about 25 min without dropping below 3K RPM. The next morning it had a rough idle and threw the drivetrain error again. Got that to go away, but the SES light is still on.

Next day the car is idling a little smoother, yet still stuttering during some acceleration. I'm assuming that this is part of the cleaning process. I know that it's doing nothing for the carbon buildup, but my hope was the injectors may be dirty. All of this is just to give it a shot to work before taking it in to my mechanic for a closer look. Want to get a walnut shell cleaning soon as well.

Is it safe to run a third bottle in a row of Techron, and do I really need to get an oil change right now? Also, is there much of a difference between the Techron injector cleaner and the Fuel System cleaner?

[ezaircon4jc]

Originally Posted by phatchuck

I just purchased an N55 with 94K on it. It's been throwing a 'drive train malfunction' code and when it's off the SES light is on. Three weeks ago the dealer had it for a week and said they put some 'chemicals' in the DI ports to get rid of some of the carbon buildup.

Two weeks later I get the same error again with the SES light on. I call my real mechanic and he recommends a Techron fuel injector cleaner cycle. Added it to a nearly full tank of 91 octane fuel. When that was gone, added another bottle to a nearly empty tank with Sunoco 93. I also have it an Italian tuneup - driving for about 25 min without dropping below 3K RPM. The next morning it had a rough idle and threw the drivetrain error again. Got that to go away, but the SES light is still on.

Next day the car is idling a little smoother, yet still stuttering during some acceleration. I'm assuming that this is part of the cleaning process. I know that it's doing nothing for the carbon buildup, but my hope was the injectors may be dirty. All of this is just to give it a shot to work before taking it in to my mechanic for a closer look. Want to get a walnut shell cleaning soon as well.

Is it safe to run a third bottle in a row of Techron, and do I really need to get an oil change right now? Also, is there much of a difference between the Techron injector cleaner and the Fuel System cleaner?

Pretty much all OTC injector/system cleaners are diluted versions of the parent company's professional cleaners. That said, you could probably run Techron in every tank without any ill effects.

The N55 is NOT the N54 when it comes to carbon build-up. The N55 does NOT suffer the carbon build-up problems the N54 did/does. I asked my SA about walnut blasting and he said they only do it on the N55 as a "last resort" when all other attempts to rectify a problem have failed. He said they haven't needed to, or done a walnut blasting on an N55. Have you changed the plugs? Coils? A faulty plug can kill a perfectly good coil and a faulty coil can kill a perfectly good plug. I haven't heard of this on a BMW, but my last car had the same COP (Coil On Plug) set-up as my 535i and a marginally failing coil would cause an intermittent miss-fire and never through a code until complete failure; which by that time could damage the catalytic converter.

All that said, I would look to the coils and/or plugs.

[Surly73]

A couple of things....

First, fuel system cleaners don't do nearly as much in direct injection cars as they did in port fuel injection cars. The fuel is delivered right into the cylinder just before ignition. With port fuel injections the fuel is sprayed into to the intake, washes the intake valves etc... Although I still run a high-PEA (this is the key ingredient for a good, high-detergent fuel system cleaner) cleaner now and then, I don't bother as much as I used to before I had direct injection.

Second, as already pointed out, the carbon buildup/walnut blasting is mostly an N54 thing, not so much an N55 thing.

Based on all that - you probably have something else going on. I've had 8 fuel injectors replaced under warranty (and the engine only has 6 so some were replaced twice) due to DriveTrain Malfunction errors. I've also had all 6 spark plugs replaced under warranty - same reason. And I only have 40k miles.

Unfortunately I didn't get a set of coils out of the warranty too or I'd have the whole setup refreshed Your mechanic might be giving you old, pre-DI advice. Scanning the car with ISTA+ may shed some light.

You may need to start looking at injectors, coils or plugs instead of pouring in cleaners.

[phatchuck]

Originally Posted by Surly73

A couple of things....

First, fuel system cleaners don't do nearly as much in direct injection cars as they did in port fuel injection cars. The fuel is delivered right into the cylinder just before ignition. With port fuel injections the fuel is sprayed into to the intake, washes the intake valves etc... Although I still run a high-PEA (this is the key ingredient for a good, high-detergent fuel system cleaner) cleaner now and then, I don't bother as much as I used to before I had direct injection.

Second, as already pointed out, the carbon buildup/walnut blasting is mostly an N54 thing, not so much an N55 thing.

Based on all that - you probably have something else going on. I've had 8 fuel injectors replaced under warranty (and the engine only has 6 so some were replaced twice) due to DriveTrain Malfunction errors. I've also had all 6 spark plugs replaced under warranty - same reason. And I only have 40k miles.

Unfortunately I didn't get a set of coils out of the warranty too or I'd have the whole setup refreshed Your mechanic might be giving you old, pre-DI advice. Scanning the car with ISTA+ may shed some light.

You may need to start looking at injectors, coils or plugs instead of pouring in cleaners.

So, long story short - i bring it to a BMW mechanic and they get cylinder misfires. Fuel injectors are fine, and apparently the coils are relatively newer. The plugs all seem worn and old. They replaced all 6, no more misfire codes and the car has been running better than ever. It's just funny that someone would replace coils and not the plugs.

Hopefully that should solve my issue. Although I wish I could find a solution to the second gear bucking that form what I've read, is fairly common in F10s and there really is no fix. I've driven it about 3K so far, so I would assume the car has had enough time to adjust to my driving style? I've read some posts about resetting the OBC by a process that includes holding the gas pedal down w\o starting it etc. Does that even work?