Hello, I've had my 2004 BMW 545i for about 2 years now, taking it off of my father's hands after him previously owning it for about 7 years.


Important side note I have a cold air intake and an electric exhaust cutout before the last muffler. I had both of these for months prior to the new problem.


I just recently took out the front two resonators and replaced them with straight pipe. However I did a crappy job with a lot of exhaust leaks so I planned to take it into a shop to weld it in the next couple of days. Two day after I did this I was driving home and suddenly as I was accelerating the car made a loud exhaust noise, almost like the exhaust just fell off for a second, and the engine code "Engine malfunction: High loads may damage catalytic converters." something along the lines of that, appeared. The car suddenly starting running really rough and lost all of its power (talking mechanically not electrically). Luckily I was 20 seconds from my house and left the car there off the road. The next day I started it up, was idling really rough and sounded terrible, and limped my way to the exhaust repair shop hoping it would fix the problem. They were able to fix the exhaust but the rough idle was still there. I disconnected the battery hoping to reset it but it didn't do anything. I took it for a drive to see if driving it would help and as I was accelerating again the same thing happened but it then stalled. I coasted to a stop, turned it off, started it again to be met with a really jumpy idle for 10 seconds and the car stalled. The car then would not start again, it would just turn over so i towed it home.


Does anybody have any ideas what is causing this? I've asked friends and some say its lack of back pressure but I still have the two mufflers in the back and the mid resonator so I don't think that is it. I also am hearing I may need to tune due to the less restrictive exhaust setup and air intake. Is it just a coincidence this happened after I did the work on the resonators?


Any ideas help! Please let me know if you need more details about the situation.

 

Have you scanned with a code reader that can read BMW codes? We can't really do much until you have those so that we know what is happening. Carly, INPA, etc.

 

You sure you just don't need coils and plugs. Get the codes read and if it's a misfire replace them unless you know how long it's been since the plugs were replaced. Never drive these cars in limp mode if you can avoid it. It just causes more issues. Did it ever start driving right and when you punch the gas it went into limp mode. Just seems like you're having unburied fuel in the engine

 

Unfortunately I never made a decision on which code reader to buy so I am here with a standard OBD2 reader. If you recommend Carly I will buy one now.

 

I haven't checked into coils and plugs. How would you recommend checking those? Would a code reader tell whether they are good or not?

Thank you both for your response. I really appreciate it.

 

You can buy just about any BMW Code Reader. Some as little as $44. I would search on Amazon or eBay.

 

You need the codes. At this moment it doesn't matter if it's a BMW code reader or generic. You need to know what it's telling you. Once you have the generic code you can go from there. I don't know if you're in the states or not but the parts store will let you borrow there's if you don't have one. You're looking for codes in the 300's (p0300-06) or codes in the 700's (p701-2).

 

Long ago when I was a jaguar guy the motto was, "always suspect the last thing you did."

FWIW as far as code readers go, I went with a cable off ebay and INPA etc on a laptop. With this I've also been able to do a few minor coding tweaks, like getting rid of the legal disclaimer that iDrive always boots with, and adding an aux input.

I don't think "lack of back pressure" is really a thing. But if you want to put that notion to bed, it is not like it is hard to partially block the exhaust tips and see if it makes any difference to your idle. Also (just while you are waiting on a code reader), is it possible you left an o2 sensor disconnected, or anything like that?

 

Thank you all for your replies so far! I didn't touch the o2 sensors that is not the issue. I ran codes with a generic reader and well I've got every n62 code in the book.

Disclaimer: I am aware of infamous P0491 and P0492 codes. I haven't fixed it because of the price tag compared to the worth of this vehicle. I plan to in the future unless you guys think this is the overarching cause of this all, in which case i will need to figure something out.

Codes:
P0330- Random misfires detected (Kind of encases the last 6 codes)
P0441- Evaporative Emissions System. Incorrect Purge Flow
P0444- Evaporative Emission System. Purge Control Valve Circuit open
P0491- Secondary Air injection System (Bank 1)
P0492- Secondary Air injection System (Bank 2)
P0024- Exhaust Camshaft Position Timing --Over-- Advanced (Bank 2)
P0305- Cylinder 5 Misfire Detected
P0308- Cylinder 8 Misfire Detected
P0306- Cylinder 6 Misfire Detected
P0307- Cylinder 7 Misfire Detected

That is a lot to take in at one time so I am completely lost as to where to start. I am assuming that the misfires are due to the camshaft over timing, even then not sure if I am right on that one. This being said I am going with timing needs to be fixed and the purge valve needs to be replaced. Anybody have any opinions on what is actually the problem and where to start?

Anything is much appreciated!

 

See above i used a generic one for now. Do you think I need to get a more advanced one for this issue? I plan on getting a BMW specific one in a bit but I hope to solve this without one for now.