[Pete618]

Hi All,

My stock 335 runs rough once its been warmed up and re-started. It runs ok when start cold and I can drive it for about 10 to 20 minutes and it runs a little rough, but not too bad; But if I start again after that, its runs very rough.
I get an error code P0303 once warmed up, but not on cold start.
I have replaced the spark plugs and coils. (with considerable improvement after).
Spark plug #3 had normal wear. Plug 6 had some carbon build up so I was surprised that #3 had the misfire.
I did have the walnut blast cleaning a few years ago, but not sure when.
All index 7 injectors.
Injector 3 looked fairly clean on removal - no carbon or soot past the seal.
Car has 130k+ miles.
I did try a cleaning additive to this tank as well.
Exhaust smells really bad too (but not the sulfur smell) especially on start up.
I plan on running again tomorrow and pulling each plug after to check for fuel smell.
Note: In the past, I often ran the fuel very low before filling - just a bad habit. I'm thinking that may have contributed to this.

Considering the age of the car, and potential problems with the older injectors, I would just replace injectors if I could afford it, but thats a lot of cash right now - so if thats the case, I just need to be sure first.

Questions:
1. Do you think its a bad injector?
2. Can I switch injector 3 and 2 to see if I still get the #3 misfire to help pinpoint the problem?
3. Could the catalytic converter also been affected and now causing issues? (I'm asking this because the problem gets worse as the car warms up).
4. What else could it be?

Any help is appreciated! I've learned a lot about this car through all this so its been a challenge, but I could use some help at this point.

[billowusu]

Originally Posted by Pete618

Hi All,

My stock 335 runs rough once its been warmed up and re-started. It runs ok when start cold and I can drive it for about 10 to 20 minutes and it runs a little rough, but not too bad; But if I start again after that, its runs very rough.
I get an error code P0303 once warmed up, but not on cold start.
I have replaced the spark plugs and coils. (with considerable improvement after).
Spark plug #3 had normal wear. Plug 6 had some carbon build up so I was surprised that #3 had the misfire.
I did have the walnut blast cleaning a few years ago, but not sure when.
All index 7 injectors.
Injector 3 looked fairly clean on removal - no carbon or soot past the seal.
Car has 130k+ miles.
I did try a cleaning additive to this tank as well.
Exhaust smells really bad too (but not the sulfur smell) especially on start up.
I plan on running again tomorrow and pulling each plug after to check for fuel smell.
Note: In the past, I often ran the fuel very low before filling - just a bad habit. I'm thinking that may have contributed to this.

Considering the age of the car, and potential problems with the older injectors, I would just replace injectors if I could afford it, but thats a lot of cash right now - so if thats the case, I just need to be sure first.

Questions:
1. Do you think its a bad injector?
2. Can I switch injector 3 and 2 to see if I still get the #3 misfire to help pinpoint the problem?
3. Could the catalytic converter also been affected and now causing issues? (I'm asking this because the problem gets worse as the car warms up).
4. What else could it be?

Any help is appreciated! I've learned a lot about this car through all this so its been a challenge, but I could use some help at this point.

Do you get white smoke on startup? Do you also get black liquid from your exhaust?

[Pete618]

No white smoke that Ive seen, but I will watch carefully next time. Not sure on the liquid either.

[Pete618]

There is a white mist at cold start up (it dissipates quickly - smoke would stay in the air) and there is a small amount of inky sludge inside the tail pipe (not dripping out). No apparent odor of fuel.

[stewbets]

First of all, it's a good idea to get a BMW-specific code reader instead of one that gives generic codes. There could be some that you're missing. I just use the MHD app. Do you get a long crank on a warm start? Did you get around to pulling plug 3 and smelling for fuel? Those 2 things are typically going to identify a leaking injector, but it could be failing some other way. I don't think swapping injectors is a bad idea, provided you've scanned with a proper scanner and there are no other codes.

[Pete618]

I'm using an Autolink AL329 - its very basic, but might have bmw specific codes, though if it does, I'm not there yet. But there are no other fault codes registering at this time.
Business needs took over today, so my time under the hood will have to wait until tomorrow.
No long cranks - except for the last time I started after inspecting the #3 injector for some reason - but thats never been a problem.

[Saif2018]

Recommend you use INPA/Protool or MHD to check codes.

Not a good idea to use generic readers as they miss many codes.

Swapping injectors to see if misfire follows is a good idea.

I'm assuming Plugs and Coils replaced recently?

[Pete618]

Yeah, that makes sense - I was surprised there were not more codes when I hooked up. "stewbets" also recommended a BMW specific reader so thats what I'm doing next. The INPA looks good - I prefer the PC interface. Thank you!

[oilcrankinject]

When was the last time you walnut blaster your intake chambers?

[Pete618]

I think about 4 years ago