[izzy99]

RESOLVED: the issue due to carbon build up with the injectors and piston heads.
I'd soaked injector cleaner inside the piston cylinder for about an hour or 2 then crank the fluid it out of the cylinder with fuel injectors unplugged. Put everything back together and started the car to burn off the rest. Put a nice bottle of injector cleaner into the fuel tank (royal purple)


Hi All,

Thanks in an advance for helping out.

I have an on going issue with my idle since I brought the car CPO and it is modded with 59K miles, catless downpipe, bigger intercooler, BM3 tuned stage 2 91, charge pipe upgraded. Uses 94 octane, problem never solved. I have not yet update the firmware on all control units.

The work have been done resolving this issue but NEVER did
- Valvetronic Servomotor
- Valve cover gasket
- New spark plugs gapped .22"
- new air filter
- new ignition coils
- intake valves, very clean
- cleaned, MAF, MAP, Pre-MAP sensors

Problem:
during cold start/up to running temp/get worst driving for longer, the engine stumbles and hiccup with no code stored and it is happening very frequently. Low/hard acceleration on idle feels like a misfire and lack of power from 600 to 1500 RPM. I had scanned it with ISTA D, found no code. I had data logged during idle and showing:

HPFP: constant under 1300 PSI
LPFP: 84 PSI

during the hiccups: (0-5) fuel mass jumps 7 to 8 that's when hiccup occurs
http://www.bootmod3.net/log?id=5df5918cc090c631be19698c

When it is hiccuping, get worst when you drives it longer:
https://www.youtube.com/watch?v=hm12...ature=youtu.be

when it occurs, the ignition timing seem to be a jump. see 1 second mark with huge spike in RED
http://www.bootmod3.net/log?id=5df84b1fc090c6327e156b8a


Please help!!! I couldn't figure out this issue or certified BMW mechanic.

[thejeremyman9]

Post is a little confusing - the issue was there when you bought the car CPO, or after modding? I assume after modding or else CPO warranty would have helped diagnose/solve.

Anyways, initial thoughts that commonly lead to these issues:

1. Intake - Doesn't look like you have one? Completely stock intake?

2. Plugs and gap. I assume you are running NGK, one step colder? Yes, i know this is recommended by PTF and others. Some cars just dont like these. Going back to stock plugs with stock gap might be your next test, assuming you haven't tried that already.

3. You could also try flashing back to stock tune, if you havent already, but unlikely to help. This would also reset adaptations (i think BM3 does this automatically on a flash).

Is OEM cold start still enabled, such as RPMs are raised on a cold start temporarily?

[izzy99]

Originally Posted by thejeremyman9

Post is a little confusing - the issue was there when you bought the car CPO, or after modding? I assume after modding or else CPO warranty would have helped diagnose/solve.

Anyways, initial thoughts that commonly lead to these issues:

1. Intake - Doesn't look like you have one? Completely stock intake?
yes it is stock

2. Plugs and gap. I assume you are running NGK, one step colder? Yes, i know this is recommended by PTF and others. Some cars just dont like these. Going back to stock plugs with stock gap might be your next test, assuming you haven't tried that already.
the plugs are NGK, I had stock plugs before and still didn't fix the problem.

3. You could also try flashing back to stock tune, if you havent already, but unlikely to help. This would also reset adaptations (i think BM3 does this automatically on a flash).
flashed it back to stock and still does the same thing

Is OEM cold start still enabled, such as RPMs are raised on a cold start temporarily?

cold start is disable


The problem occurs during cold start, drove it longer operating temp get worst everyday now. I have a video to show when it hiccups

https://www.youtube.com/watch?v=hm12...ature=youtu.be

[harkes]

1: First try to disconnect your MAF sensor to rule that out. If the car is running fine without then that is your problem -> new MAF.
2: Enable cold start. My car also had similar problem when disabled.

[izzy99]

Originally Posted by harkes

1: First try to disconnect your MAF sensor to rule that out. If the car is running fine without then that is your problem -> new MAF.
2: Enable cold start. My car also had similar problem when disabled.

I have ruled out MAF sensor and cold start, it's not at fault.

when it occurs, the ignition timing seem to be a jump. see 1 second mark with huge spike in RED

http://www.bootmod3.net/log?id=5df84b1fc090c6327e156b8a

I was driving very hard before when back to normal idle

[izzy99]

BUMP!

[izzy99]

THANK YOU EVERYBODY,

RESOLVED: the issue due to carbon build up with the injectors and piston heads.
I'd soaked injector cleaner inside the piston cylinder for about an hour or 2 then crank the fluid it out of the cylinder with fuel injectors unplugged. Put everything back together and started the car to burn off the rest. Put a nice bottle of injector cleaner into the fuel tank (royal purple)

[Tpriest7893]

Just so I understand, you only poured a bottle of the cleaner in or did that and the other?

[Pray for Mojo]

Did you run injector cleaner in the tank ever before or just once you had issue? I usually put a reputable brand (Techron, Royal Purple ect) in a tank every 10k km.

[Polo08816]

Originally Posted by Tpriest7893

Just so I understand, you only poured a bottle of the cleaner in or did that and the other?

Yeah, I'm not quite sure how he accomplished this. Removed the spark plugs and flooded the cylinder with injector cleaner?

[izzy99]

Originally Posted by Polo08816

Yeah, I'm not quite sure how he accomplished this. Removed the spark plugs and flooded the cylinder with injector cleaner?

Yes but you do not want to hydro lock the engine. The fuel injectors cleaner will loosen up the carbon on the piston head. You can also crank the engine with the injectors unplugged with the piston head that's already soaked to the top so the injectors cleaner can reach the injectors itself and that will remove any carbon build up. It may be complicated but will write up a procedure for everybody that's having the same problematic that engine never throw out any codes.

[Polo08816]

Originally Posted by izzy99

Yes but you do not want to hydro lock the engine. The fuel injectors cleaner will loosen up the carbon on the piston head. You can also crank the engine with the injectors unplugged with the piston head that's already soaked to the top so the injectors cleaner can reach the injectors itself and that will remove any carbon build up. It may be complicated but will write up a procedure for everybody that's having the same problematic that engine never throw out any codes.

So my fuel injector in cylinder #6 failed in a stuck open position this past summer at the track. I had 115,000 miles on my N55 at that point.

I ended up replacing a good portion of the fuel system preventatively. All 6 fuel injectors, high pressure fuel pump, and low pressure fuel pump.

[izzy99]

Originally Posted by Polo08816

So my fuel injector in cylinder #6 failed in a stuck open position this past summer at the track. I had 115,000 miles on my N55 at that point.

I ended up replacing a good portion of the fuel system preventatively. All 6 fuel injectors, high pressure fuel pump, and low pressure fuel pump.

did it fixed the problem?

[izzy99]

Originally Posted by Pray for Mojo

Did you run injector cleaner in the tank ever before or just once you had issue? I usually put a reputable brand (Techron, Royal Purple ect) in a tank every 10k km.

I'd ran it few times but it didn't solve the problem before. Still that same hiccup in the video. I'd spent countless time and money into solving this problem but nothing worked until now. It idle like a charm.

[harkes]

Originally Posted by izzy99

RESOLVED: the issue due to carbon build up with the injectors and piston heads.
I'd soaked injector cleaner inside the piston cylinder for about an hour or 2 then crank the fluid it out of the cylinder with fuel injectors unplugged. Put everything back together and started the car to burn off the rest. Put a nice bottle of injector cleaner into the fuel tank (royal purple)

This sound strange to me. I have been running methanol injection the last 4 years/50000km with minimal carbon buildup. My car is still having these cold start hiccups but ONLY with cold start switched off.

[izzy99]

Originally Posted by harkes

This sound strange to me. I have been running methanol injection the last 4 years/50000km with minimal carbon buildup. My car is still having these cold start hiccups but ONLY with cold start switched off.

it is not the valves but the piston head and cylinder....... also I put in a bottle of engine restore into the engine

[harkes]

Originally Posted by izzy99

it is not the valves but the piston head and cylinder....... also I put in a bottle of engine restore into the engine

Right. I get that. Just had a bore scope picture of my valve to show how little carbon there is. You never walnut blast the piston so in terms of carbon build up the valves must be the worst

[Polo08816]

Originally Posted by izzy99

did it fixed the problem?

It sure did.

[izzy99]

Originally Posted by harkes

Right. I get that. Just had a bore scope picture of my valve to show how little carbon there is. You never walnut blast the piston so in terms of carbon build up the valves must be the worst

I checked my valves too and it was clean on the N55. I don't see much of build up and same as your picture. You don't want to walnut blast the piston head. That's why i soaked it with injector cleaner instead that also loosen up any inside there. It will burn it off. Cheap method but it worked for me

[harkes]

I bought some Chevron Injector Cleaner that I will add with next tank to see if it improve anything.

Nobody has a log of the car misbehaving during cold startup so we can try to analyze instead of just guessing???