Rough idle, RPM surge, multi-cylinder misfires - shop recommending injectors, need second opinion

[deshun]

Hey everyone,Looking for some guidance before I commit to a very expensive repair.

Vehicle is experiencing:
• Rough idle and misfires on multiple cylinders
• RPM surging (revs up high, then stabilizes itself)
• Check Engine Light comes on after surging • Occasional squealing noise on startup
• Light smoke from exhaust at times with a chemical/burning smell

I already replaced all spark plugs and ignition coils, but the issue persists.
A shop diagnosed the car and pulled the following DME codes: • 29D2 – Combustion misfires, cylinder 6 • 29CE – Combustion misfires, cylinder 2 • 29D0 – Combustion misfires, cylinder 4 • 29CC – Combustion misfires, several cylinders

They road-tested the vehicle while monitoring misfire counts (misfires on multiple cylinders across both banks).Smoke test showed no external vacuum leaks.Fuel rail pressure was within spec.
They noted:
• Bosch spark plugs installed
• Aftermarket (unmarked) coils installed
• Injectors: Bank 1 index 08, Bank 2 index 07

Based on this, they recommended replacing all injectors, plugs, and coils (~$5k total).
Additional info:
• When removing the oil cap while the engine was running, it came off easily. Engine continued running, but a small amount of vapor/smoke was present.
• Symptoms seem more like air/crankcase control than fuel (RPM hunting, self-correction, startup squeal, burning smell).
Before I approve injector replacement, I wanted to ask:
• Would mixed injector index numbers alone justify full injector replacement?
• Could this be related to valve cover / PCV system, oil contamination, or an intake/charge pipe issue that a smoke test might miss?
• What additional tests would you recommend to confirm injectors before replacing all six?
Appreciate any insight trying to avoid throwing parts at it without solid confirmation.

He’s got about 160k miles and is a 09

[Redd]

Originally Posted by deshun

• Aftermarket (unmarked) coils installed

This is your issue. Aftermarket coils don't work.

[deshun]

Originally Posted by Redd

This is your issue. Aftermarket coils don't work.

I would think it was that but these are the same coils I used my last few tune ups and and haven’t had any previous issues

[tracer bullet]

I'd be thinking about new coils all around, may as well do new plugs while you are at it. Something like $300 for all of it, and you can do it yourself. Maybe 2 hours of work going slowly. Then clear all the codes, go for a drive, see what comes back.

Only then start considering injectors or any other work. And do not pay a shop $5000 for this.

At your mileage there's a more than decent chance plugs and coils could be swapped out. It is throwing parts at it, which I normally hate, but they're very common maintenance items and if you plan to have the car a while they are worth it.

[deshun]

Originally Posted by tracer bullet

I'd be thinking about new coils all around, may as well do new plugs while you are at it. Something like $300 for all of it, and you can do it yourself. Maybe 2 hours of work going slowly. Then clear all the codes, go for a drive, see what comes back.

Only then start considering injectors or any other work. And do not pay a shop $5000 for this.

At your mileage there's a more than decent chance plugs and coils could be swapped out. It is throwing parts at it, which I normally hate, but they're very common maintenance items and if you plan to have the car a while they are worth it.

Do you still think it’s the coils if I was having this issue before I changed them and it just continued after I did the tune up? One day it was doing perfect and the next morning it’s rpm went crazy and CEL and it burnt through a pack of spark plugs in one day

[tracer bullet]

Originally Posted by deshun

Do you still think it’s the coils if I was having this issue before I changed them and it just continued after I did the tune up? One day it was doing perfect and the next morning it’s rpm went crazy and CEL and it burnt through a pack of spark plugs in one day

Ugh, sorry. I re-read your first post. I really do try to actually read things, but I totally missed the line where you said you already changed them.

If this was a sudden kind of change, it makes me think... bad gas? Plugs and coils are a creeping kind of thing, they create issues of course but tend to be progressive failures, slowly getting worse, not sudden. Bad gas could cause sudden problems. I know that sounds like a thing that's not real, but it is, rare but real. Draining a tank isn't trivial but it might give you something to consider.

Have you cleared all the codes, runt he car and pulled them again? If not, it's really the first thing to do for almost every single thing that needs to be troubleshooted on a BMW.

I'd consider another shop, or two, or even the dealer. Someone out there has a much better routine to find issues than to quote $5k in parts swapping, hoping for the best.

Sorry I didn't see that you already replaced parts. I would actually consider them again, but given that the issues were occurring before and after that, it sounds like they are likely not at fault. It is possible to replace bad parts with bad parts, but somewhat odds are low.

[deshun]

Originally Posted by tracer bullet

Ugh, sorry. I re-read your first post. I really do try to actually read things, but I totally missed the line where you said you already changed them.

If this was a sudden kind of change, it makes me think... bad gas? Plugs and coils are a creeping kind of thing, they create issues of course but tend to be progressive failures, slowly getting worse, not sudden. Bad gas could cause sudden problems. I know that sounds like a thing that's not real, but it is, rare but real. Draining a tank isn't trivial but it might give you something to consider.

Have you cleared all the codes, runt he car and pulled them again? If not, it's really the first thing to do for almost every single thing that needs to be troubleshooted on a BMW.

I'd consider another shop, or two, or even the dealer. Someone out there has a much better routine to find issues than to quote $5k in parts swapping, hoping for the best.

Sorry I didn't see that you already replaced parts. I would actually consider them again, but given that the issues were occurring before and after that, it sounds like they are likely not at fault. It is possible to replace bad parts with bad parts, but somewhat odds are low.

I’ve cleared code and reinstalled new plugs but it will run good for a day and start misfiring again I’m thinking it can be the pcv and just replacing the head gaskets

[SwankPeRFection]

First of all, this needs to be moved out of the detail sub forum. Second of all, post pics of what the plugs look like when you pulled them. If they’re black, you’ve got leaky injectors, but we need to see them and also, what’s the specific car model so we know what engine is in it? You didn’t say any of this.

[M5Rick]

If it came on suddenly could be gas contamination, water in it, what fuel did you use and where d'ya live?

[Eris496]

purge valve?