[jsjaime]

Hey!

I bought a N55 F30 (manual, xDrive) in July-August 2023 from auction. The seller was the shop from the former owner and had done regular maintenance. According to the previous owner, the only mechanical mod the car has is a Turner Motorsport axle-back exhaust system.

Before getting the car, the seller stated that sometimes the CEL turned on due to the inlet turbo pipe getting loose.

When getting the car, the CEL was on (solid). I bought the Carly's scanner and found that the CEL code was "118001 Mixture control: Fuel-air mixture too lean", so I guessed it was due to a loose pipe. I did a visual check, but everything looked to be tight and in place.

I sent the car to a local shop that found that the aftermarket inlet pipe was defective and changed it for an OEM one. They also found that the car had a tune (which wasn't disclosed by the seller).

Changing the pipe did not resolve the issue, although the car showed no leaks in the smoke test or pressure test (the car keeps a steady pressure in the intake, indication of an air tight system). They suggested to replace the oxygen sensors, which they did for with ones. That didn't work, so they swapped the MAF with a spare one they had. The CEL is still there.

Finally, they said that they have checked everything that they could and the system is air tight. They suggested that the CEL might be due to a valveless (flapless?) exhaust system and referred me to a tuner so he could "bypass" the valve sensors/system.

I got home and started looking for more information on the valves' sensors/system and saw that all codes related to that did not trigger a CEL, but a regular code. So before I keep pouring money into the car, I wanted to check with you if you might have any alternative ideas.

By the way, the car runs great. If it wasn't for the CEL, I wouldn't mind driving it hard.

Thanks!

[thejeremyman9]

Probably need some sort of datalog to see what is going on.

[jsjaime]

Thanks, before going to the tuner I'll try to get a datalog with Carly's...

[thejeremyman9]

Originally Posted by jsjaime

Thanks, before going to the tuner I'll try to get a datalog with Carly's...

If the car was tuned, do you have access to the tuning platform to datalog? Will be far better than logging with other software

[jsjaime]

Originally Posted by thejeremyman9

If the car was tuned, do you have access to the tuning platform to datalog? Will be far better than logging with other software

I didn't even know it had a tune until a few weeks ago, hehe. I'll ask the seller for more info.

[n55david]

The exhaust system will have zero effect on if the car is running lean or not. You have a leak in the intake system between the turbo and throttle body or at the intake manifold/valve cover or could be a fueling issue that's going to be hard to track down. Need logs.

[CalibratEd]

Have you had a chance to log the car?

[jsjaime]

Actually, I haven't. Sorry for the delayed response, has been a busy season. Do you know someone who could help me with this around the DMV area? I have Carly's, but not sure if that would work.

[jsjaime]

BTW, this response came from the seller:

"The car does not currently have a tune loaded on it- we check ECUs and return cars to stock condition in some cases depending on how heavily they're modified, though it isn't a very common occurrence. We maintained the vehicle for the prior customer, but I will still call him and ask."

[CalibratEd]

I would look into what N55david recommended. It's going to be hard to further assist you without logs. I am not familiar with the Carly scanner.

[jsjaime]

Thanks all of you who tried to help!

Coming back after resolving the issue, which ended up being much more expensive than I anticipated.

It was a bit hard to find a shop to work on the car, as three shops didn't take the car when they found it had a tune. Fortunately I found a shop that is performance focused and had no issue taking the car.

So they first tried to diagnose the car and he said that the tune was actually covering up some of the codes and wasn't letting him look in deep. Not sure exactly how as I have almost no experience with electronics/tuning. He had to reprogram the car and then a 134F01 code showed up (valvetronic). I had scanned the car several times (with Carly) and had never seen that code.

The valvetronic motor was binding (although not permanently) and that was letting in more air, which is why the car was running lean. He tried reprogramming the motor, but it didn't really work in the end. So they ended up replacing the valvetronic motor, eccentric shaft and the valve cover. It looked old and there is no record of it being replaced ever, so it was a good chance to put a new one back on. I forgot to mention that it's almost at 150k miles.

The shaft's gears were pretty worn, so it was a good call.

What's funny about all of this is that the car was running pretty good and I only feel a slight difference in power after the repair, maybe on low revs, but it can be just be my own bias. I've seen threads on cars showing up the valvetronic code and they seem to go crazy.