[Jaxmemo]

Hello,

My car is stuck in limp mode and I can't seem to figure out what's causing it..

Current state of car:
2010 335i with 68,000 miles, original turbos, original fuel pump, no ECU flashes or piggybacks, after market charge pipe, aftermarket air intakes, new spark plugs.

Warning Light(s):

Before all this happened, I had 2c6b and 2c31 for the o2 sensors. I had this before, it would come and go but never caused a limp mode. Other than o2 codes, I have no other codes.

What happened before limp mode:
Before limp mode, I went out for dinner, the car was driving normal except for the lean fuel smell and not so smooth engine during idle which I had previous (possibly from the o2 sensor issue). About an hour or two later, I got back in the car, I noticed it was slow, turbos not spooling and since then, the car will not get out of the limp mode. I tried to look and listen for air leaks and couldn't find anything and the charge pipe still appeared in place. I originally thought it could be the HPFP but the car starts immediately. The idle is still not as smooth at stop, it has a light stutter. The fuel does still smell lean from the exhaust but no fuel smell from the engine bay so I am guessing it's not the injectors. Lately, it did feel like I was having misfire or light popping sound when I gun it and shift at high RPMs(Automatic tranny) so I have no clue what that light popping/backfire sound is coming from.


Any thoughts/feedbacks on the limp mode and the light popping/backfire sound?? Any and all comments will be greatly appreciated.

[robthewrench]

Popping / backfiring is unburned fuel in the exhaust system. Could be either too rich or too lean. Rich is more common and way less dangerous. Too lean can create severe pre-ignition (knock) issues.

[Jaxmemo]

Thanks Rob. What do you think causes the rich/lean issue? Could that also be the cause for the idle not being smooth at a stop?

I am going to a muffle shop to perform exhaust system leak test to see if I have any leak from the downpipe and back which might be the main culprit for the o2 sensor issue..

[BSM n54iS]

O2's...

[Jaxmemo]

Originally Posted by BdSM n54iS

O2's...

Do you think that could also be the cause for the limp mode even though I had the o2 sensor issue for two months and limp mode started last night?

[Underground6t9]

Sounds like injectors

[BSM n54iS]

Originally Posted by Underground6t9

Sounds like injectors

easy way to tell that, pull your spark plugs op and see if there is a fuel smell to them or in hole there.

But if you have o2 codes with no aftermarket anything, then reason says you have bad o2's right? Bad o2's can cause the dme to cause you to be running too rich/lean, long enough of running your dme like this will cause all sorts of bad shit

[Jaxmemo]

Originally Posted by BdSM n54iS

easy way to tell that, pull your spark plugs op and see if there is a fuel smell to them or in hole there.

But if you have o2 codes with no aftermarket anything, then reason says you have bad o2's right? Bad o2's can cause the dme to cause you to be running too rich/lean, long enough of running your dme like this will cause all sorts of bad shit

That's a great advice from you and underground..

First I'll see if there are any exhaust leaks since that's easiest (muffler shop does it for free). Second I'll test the injectors by pulling the spark plugs. They should be dry and not smell like fuel, right?

[BSM n54iS]

Originally Posted by Jaxmemo

That's a great advice from you and underground..

First I'll see if there are any exhaust leaks since that's easiest (muffler shop does it for free). Second I'll test the injectors by pulling the spark plugs. They should be dry and not smell like fuel, right?

correct, nor oil

[Jaxmemo]

Limp Mode
Upon further inspection, i noticed that one of the two vacuum lines that are coming from the vacuum canister across the valve cover and connect to another larger pipe behind the oil filter cap was not connected to the nipple. I reconnected it and the limp mode was gone

Exhaust leak inspection
I took the car in to a muffler shop where a gentleman inspected and listen using some kind of stethoscope and on the downpipes and pipes, he didn't think there was any exhaust leak.

O2 sensors
The muffler guy connected some O2 sensor reader to the OBDII and read the readings off the o2 sensors at idle and varies RPMs. He said the temp and readings were good and all were within 10% of reading of each other. He didn't think the sensors are defective.


Injectors
Based on the recommendations above, I inspected the spark plugs and took the pictures below. #4 did have fuel odor while others had stains and not as noticeable fuel odor. Let me know your thoughts?? The spark plugs are less than a month old, prob has around 500 miles on them..

Also, noticed that the part number of my current injectors are as follows:13 53 7 585 261-11 I don't believe this part number qualifies under he extended warranty based on the technical document I read online. Any feedback?

Questions for the experts

1) Do you think the tiny vacuum line is the cause of the limp mode? The line is so thin, it's hard to believe it could be the cause of the limp mode.

2) Any comments or feedback on the o2 sensor readings? Should I just go with what he said?

3) Based on the pictures below, do you think injector #4 is possibly bad? Do you think any other injector is bad or almost going bad, considering the stain? Reminder, those spark plugs are less than 1 month old, has less than 500 miles on them..


[IMG][/IMG]

URL=http://s17.photobucket.com/user/jaxmehmet/media/FullSizeRender_3_zpsbf3q3d5s.jpg.html][/URL]

[Jaxmemo]

Also meant to ask my question #4,

4) Could the injector/spark plug issue be the cause of the popping / backfire sound I hear at times based on the pictures?

[Underground6t9]

Looks like injector #4 or the coil could be causing your misfire.

[Jaxmemo]

Originally Posted by Underground6t9

Looks like injector #4 or the coil could be causing your misfire.

Thanks for the reply. How can I determine which one it is (coil vs. injector)? I have the ISTA+ OBDII scanner, will that help on any way?

[Underground6t9]

Originally Posted by Jaxmemo

Thanks for the reply. How can I determine which one it is (coil vs. injector)? I have the ISTA+ OBDII scanner, will that help on any way?

Im leaning towards injector since you smelled fuel.

[Jaxmemo]

Thanks for your help! My O2 lights were out, now they are back on again. I was also thinking the injector is bad as well. We'll see what the dealer diagnoses.

[Jaxmemo]

Update: to rule out the ignition coil #4, I replaced the coil. The engine light is still on for the O2 sensor. I am now leaning more towards injector #4 being bad.

As for the o2 sensor lights, I am still unsure if it's lean fuel odor from exhaust is from injectors or bad o2 sensor.

[Jaxmemo]

Update: replaced bank 1 sensor 1 o2 sensor yesterday. SES 2c31 light has been off. Here is a pic of the sensor replaced

[Underground6t9]

That's the result of running too lean. I would replace the injector with a used one at the very least.