Diagnosing Hesitating/Misfiring X35i with No Codes

[ClutchKickChris]

Hey guys,

SO I replaced both of the camshaft sensors with new and..... not really an improvement

Maybe it drives 10-20% better but still the hesitation and misfiring feeling is there. Not sure where to go now.

[SB1120]

I found a thread on another forum and they had a similar issue with their n55. They claim to have resolved the rough idle by filling each cylinder with injector cleaner through the spark plug hole, then extracting (and cranking to expel the remainder) to loosen carbon deposits on the piston heads.

He may be on to something..

I have used chevron fuel system cleaner a couple times in the last 1500 mi or so and there seems to be a slight improvement? It’s that or the warmer weather is helping?... Again, I have new plugs, coils, and injectors, cleaned intake valves. I will say, plugs and injectors did come out with a considerable amount of carbon on them so I can only imagine what the pistons look like.

I was thinking worn valve guides as a culprit (at 186k) but I don’t really have the accompanying noticeably smoky exhaust.

[ClutchKickChris]

Does yours idle rough? Mine has zero issue idling. It's only under light load acceleration 1500-3000rpms that it feels like its misfiring/hesitating/bucking.

I ran a bottle of chevron techron concentrate through it a few weeks ago but zero change in issues.

[SB1120]

Originally Posted by ClutchKickChris

Does yours idle rough? Mine has zero issue idling. It's only under light load acceleration 1500-3000rpms that it feels like its misfiring/hesitating/bucking.

I ran a bottle of chevron techron concentrate through it a few weeks ago but zero change in issues.

Yes, especially once warmed up. If I gently creep in drive, letting the brakes drag a bit it can be felt. Slight hesitation *sometimes* at partial throttle.

Oil filter cap is pretty recent. Replaced because the center part would no longer snap in place.

On the note of VANOS- I’ve read other N5X threads where members replaced the little VANOS non-return valves which have a micro screen on the end. I have not checked to see if mine are dirty and I’m not totally convinced it would do much in terms of the idle.

[andrewwynn]

My client n52 motor had similar problems cleared up when I changed the oil filter cap which was apparently letting oil past the filter and messing up the oil pressure to the vanos. If your scanner has graphing, plot vanos actual vs requested angle and see if it's keeping up with demand. Vanos sluggish response or disa sluggish response can cause the low rpm moderate load hesitation described.

[ClutchKickChris]

I checked the oil filter housing cap, and it's a little wiggly, but by no means broken/missing. Is this considered OK?

[SB1120]

Originally Posted by ClutchKickChris

I checked the oil filter housing cap, and it's a little wiggly, but by no means broken/missing. Is this considered OK?

Normal. The critical part is that the tip where the little o-ring lives is intact.

[andrewwynn]

I was getting vanos related errors on customer n52 with wiggly center. They went away after replacing the cap

[SB1120]

Originally Posted by andrewwynn

I was getting vanos related errors on customer n52 with wiggly center. They went away after replacing the cap

If the tiny o-ring is intact and the filter snugly fits in the oil filter housing, oil pressure and flow will be where it needs to be. I worked on a 328i that somehow had no center, discovered during an OFHG replacement. No codes but the filter was certainly doing little to nothing just sitting in there

[ClutchKickChris]

You know what, at this point for $40 I'll try it.

Also ordering a new heater control valve and Vapor Canister Purge Solenoid since they also need replacing. This car is a never ending problem lately...