2009 BMW 328i xDrive Service Engine Soon Light - Rough Idle

[JGaulard]

I took my car (2009 BMW 328xi) out for a drive last night and not more than a quarter mile from my house did the "Service Engine Soon" light come on. A split second before that, I noticed a power drop from the engine and then the car began stuttering. I was climbing a hill and I don't think the car would have made it up if I kept going. I stopped and there was a very rough idle. I turned around and came home. I turned the car off and then started it again. Nothing changed. The rough idle was still there. I was hoping the problem would disappear if I "reset" the car by turning it off, hoping it was a fluke. It wasn't. There's a real problem. Any ideas or suggestions? It seems like some sort of misfire. At least, that's what it feels like.

 

[LukeLewis]

Nine times out of ten it's a bad spark plug or coil. How many miles do you have on the car?

 

[JGaulard]

Nine times out of ten it's a bad spark plug or coil. How many miles do you have on the car?

There are about 60,000+- miles on the car. It's been running fine, so this is weird. The problem sprang up out of nowhere. It was very sudden, like something just "went bad." Do spark plugs do that?

 

[LukeLewis]

There are about 60,000+- miles on the car. It's been running fine, so this is weird. The problem sprang up out of nowhere. It was very sudden, like something just "went bad." Do spark plugs do that?

Can you test the codes? You'll need an OBDII code reader tool to see what that check engine light is trying to tell you, although I can almost guarantee it's a coil. I've also seen instances where a fuel pump sensor was acting up, causing a similar symptom.

 

[JGaulard]

Can you test the codes? You'll need an OBDII code reader tool to see what that check engine light is trying to tell you, although I can almost guarantee it's a coil. I've also seen instances where a fuel pump sensor was acting up, causing a similar symptom.

Okay, I own a AutoPhix 7810 code reader that I bought a while back. I just started the car and tested the codes. Here's what I'm seeing:
29D1 Combustion Misfire Cylinder #5
I think you're right. Either a plug or a coil is bad.

 

[LukeLewis]

Okay, I own a AutoPhix 7810 code reader that I bought a while back. I just started the car and tested the codes. Here's what I'm seeing:
29D1 Combustion Misfire Cylinder #5
I think you're right. Either a plug or a coil is bad.

Yup, on the 328s, it's usually a plug or coil. At least you diagnosed it properly. I've seen people go to shops to get that diagnosis, costing them upwards of $125. Many auto parts stores will do it for free though. Also, just do you know, when plugging the diagnostics tool in to read the codes, the "Check Engine Soon" light needs to be on, so there's something to read. Basically, you need to be experiencing the problem at the time.
Now you know the cylinder. You have a choice; buy one plug and coil or do all six of both. I would suggest you replace everything. At 60,000 miles, it's the best course of action. These parts are pretty cheap. You should be able to pick it all up online for under $200.

 

[JGaulard]

Yup, on the 328s, it's usually a plug or coil. At least you diagnosed it properly. I've seen people go to shops to get that diagnosis, costing them upwards of $125. Many auto parts stores will do it for free though. Also, just do you know, when plugging the diagnostics tool in to read the codes, the "Check Engine Soon" light needs to be on, so there's something to read. Basically, you need to be experiencing the problem at the time.
Now you know the cylinder. You have a choice; buy one plug and coil or do all six of both. I would suggest you replace everything. At 60,000 miles, it's the best course of action. These parts are pretty cheap. You should be able to pick it all up online for under $200.

Thanks for the help! I just ordered a few things from RockAuto:
(6) BOSCH 0221504470 Ignition Coil - $18.14 ($108.84)
(6) CHAMPION 9775 Iridium Spark Plug - $5.37 (31.62)
With 5% discount and shipping, everything came up to $152.77. Not bad. I've also been watching a few videos on the repair. Seems straightforward. Also, RockAuto definitely had the best prices. AutoZone wanted $56.49 for each coil and Advance Auto Parts wanted $70.99. But wait, with their discount, I could pick it up for $60.34. Gee thanks.

 

[LukeLewis]

Thanks for the help! I just ordered a few things from RockAuto:
(6) BOSCH 0221504470 Ignition Coil - $18.14 ($108.84)
(6) CHAMPION 9775 Iridium Spark Plug - $5.37 (31.62)
With 5% discount and shipping, everything came up to $152.77. Not bad. I've also been watching a few videos on the repair. Seems straightforward. Also, RockAuto definitely had the best prices. AutoZone wanted $56.49 for each coil and Advance Auto Parts wanted $70.99. But wait, with their discount, I could pick it up for $60.34. Gee thanks.

Excellent. Let me know how the repair goes.

 

[JGaulard]

I just took the plastic cover off the engine and found a large mouse next underneath. I had to pull my vacuum out to suck up all the leaves and pieces of cushion. Not a nice surprise.

I pulled out one of the coils. It's got a part number of v 7594937 80-01 written on the side of it. Take a look.



I read that the BOSCH 0221504470 has superseded this older model. I'm hoping that's true because I ordered six of them. The two parts look identical on RockAuto's website.

I read this on the e90post website:

"Question is, if my car came with the Bosch V 7594937 80-01 (9 221 504 470), what's the best replacement option? I'm looking for 100K+ miles of reliability over saving a few bucks. That said, improved awesomeness wouldn't hurt."

"That's what you should use. The earlier model years came with different coils which have been superseded by yours, but 0 221 504 470 is the latest one for your car. It's also known as Bosch 00044. That's likely what they put in to replace your broken one. You might want to double check that that's what's in there, and then just go ahead and get 5 more of the same."

Sounds good to me.

UPDATE:

I made the repair on my BMW yesterday. It took me all of 30 minutes to finish everything. Granted, I did remove the covers the day before so the coils and plugs were exposed, but that only took a few minutes and was a total of fewer than 15 bolts/screws. This really is an easy job. Once the diagnosis is made with the code reader, it's simple from there. I heard that the #4 cylinder coil is a challenge to remove because of an obstruction. I can definitely see how that one can be tough. I luckily didn't have a problem with it though.

I did one cylinder at a time. I pulled the coil off the plug and then removed the spark plug. Reinstalled the new one, popped the new coil on and just repeated the process six times. Once finished, I started the car and everything was smooth. I swear the car runs better now. Hopefully it'll get better gas mileage too. I heard that can happen if the plugs/coils are in bad shape. Thanks for your help. All I need to do now is reconnect the code reader to clear the check engine soon dash light.

Also, I just wanted to mention for anyone attempting this job, you'll not only need some sockets to remove the covers and the plugs, but you'll also need some allen/hex and torx wrenches. I forget what sizes they are, but you won't be removing the stabilizer bar or plastic cover without them.