E90 320i - Fuel Pump

[DarrylvanNiekerk]

A question for the more technically minded of you please.

I rebuilt my N46 (e90 320i) engine.
New sleeves, rings and bearings. New valve stem guides and seals, new head gasket. Great compression at 13 bar, timing is spot on using timing tool. New sparks & coil packs, cleaned MAF and inlet manifold and replaced oil suction as well as oil separator. Stripped and assessed oil pump, all in order. Injectors were sonically cleaned and tested and when I turned the car over with the fuel rail out the spray patterns looked good. Ran the engine in with SAE 30 for 1000km then changed to Liquimoly 5W30. I thought the oil might be too thin so changed to 10W40 after 7500km but I think she runs better on 5W30.

The issue I have is a slight hesitation at low revs and a random rough idle on start up sometimes. If I slow down for a speed hump and accelerate from low rpm in second there is a lag before she picks up. I originally thought the oil was too thin and the VANOS was battling hence the oil change but the issue is still there with the ticket oil. Sometimes when I start the car in the morning or even after the car has sat for a few hours the idle is lumpy, not quite a misfire, but slightly rough. I can feel it battling but then after a few kms it settles and idles smoothly. There are no codes and for the most part the engine runs really well so my thoughts go to the fuel pump.

From my basic research it seems a problematic fuel pump can cause all of the issues I am experiencing and it is an inexpensive and simple fix unless I am missing something.

Does anyone have any input or suggestions before I go down this rabbit hole?

Car has 184000km but engine only has about 12000km on it.

Thank you in advance.

 

[Solo Man]

I once helped my neighbour who had an E90 323i which started having problems idling. The revs would fluctuate quite badly. My diagnostic tool said it was solenoid valves which i replaced but made no difference. After he had the tappet cover gasket replaced due to oil leaks around the old gasket the car would idle normally. I kept the old solenoids and after i cleaned them one was used on another friends 135i and it fixed his problematic solenoid, so i am convinced it was not solenoids on the 323i. What i am trying to say is that i expect an air leak some where around the tappet cover packing. Hope this helps.

 

[DarrylvanNiekerk]

I once helped my neighbour who had an E90 323i which started having problems idling. The revs would fluctuate quite badly. My diagnostic tool said it was solenoid valves which i replaced but made no difference. After he had the tappet cover gasket replaced due to oil leaks around the old gasket the car would idle normally. I kept the old solenoids and after i cleaned them one was used on another friends 135i and it fixed his problematic solenoid, so i am convinced it was not solenoids on the 323i. What i am trying to say is that i expect an air leak some where around the tappet cover packing. Hope this helps.

So I cleaned the solenoids very well, they click solidly when power is added.

I was battling with a small oil leak at the vacuum pump so I ended up running a small bead of RTV around the entire tappet gasket and haven't had a drop of oil leak since then. I replaced the oil filler cap too. I don't suspect any air is getting into the tappet cover as for the most part the idle is bang on and doesn't fluctuate at all.

I did see my fuel trims on 1 & 3 are pulled slightly and on 2 & 4 are pushed slightly so if anything there may be a small air leak at the exhaust manifold or even at the injectors?

I would say 9 times out of 10 she fires perfectly and settles into a clean idle but that 1 out of 10 can be completely random from either a cold or hot start.

Sometimes after a hot start when I try to pull off she bogs completely and I have to give the engine a few moments to settle before trying again.

 

[Mytfine]

If its not pulling any codes i only can suggest you test your injectors again, sounds like she is flooding. Google how to read spark plugs and check from there. If one or two injectors are mis behaving the plugs will tell you all yo need to know.

 

[DarrylvanNiekerk]

If its not pulling any codes i only can suggest you test your injectors again, sounds like she is flooding. Google how to read spark plugs and check from there. If one or two injectors are mis behaving the plugs will tell you all yo need to know.

Yeah, I'll give that a whirl.

I got a lot of advice from an ex BMW mechanic and an old school racing mechanic friend during the rebuild. I did take the sparks past my racing mechanic friend a while back and he checked them out and reckoned they looked pretty even with a clean burn.

It initially took me a while to get her running properly in the beginning as one 02 Sensor was faulty and the post CAT sensors were disconnected. The engine would pop a bit which my friend reckons is more of a lean condition, he also felt the exhaust smelled a bit lean.

The car does pop a bit when the idle is off so it all seems a little weird. I do wonder if the old 02 Sensor is not working properly hence the difference in the fuel trims.

Since there are a few thousand kilos more on the clock it would probably be a good idea to check sparks again and see where things are. It's not a huge amount of work to take the covers and stiffener bars off so I can pull the fuel rail at the same time and check the injector spray patterns again.

 

[RUDEBOY]

Hi, I had the same issue at one stage and I replaced the eccentric shaft together with the Valvetronic on my N46, after the repair the engine was much more responsive when tapping the accelerator the idling came down nicely after revving up before the engine would almost stall when the revs come down.

I rebuilt my N46 (e90 320i) engine.
New sleeves, rings and bearings. New valve stem guides and seals, new head gasket. Great compression at 13 bar, timing is spot on using timing tool. New sparks & coil packs, cleaned MAF and inlet manifold and replaced oil suction as well as oil separator. Stripped and assessed oil pump, all in order. Injectors were sonically cleaned and tested and when I turned the car over with the fuel rail out the spray patterns looked good. Ran the engine in with SAE 30 for 1000km then changed to Liquimoly 5W30. I thought the oil might be too thin so changed to 10W40 after 7500km but I think she runs better on 5W30.

The issue I have is a slight hesitation at low revs and a random rough idle on start up sometimes. If I slow down for a speed hump and accelerate from low rpm in second there is a lag before she picks up. I originally thought the oil was too thin and the VANOS was battling hence the oil change but the issue is still there with the ticket oil. Sometimes when I start the car in the morning or even after the car has sat for a few hours the idle is lumpy, not quite a misfire, but slightly rough. I can feel it battling but then after a few kms it settles and idles smoothly. There are no codes and for the most part the engine runs really well so my thoughts go to the fuel pump.

From my basic research it seems a problematic fuel pump can cause all of the issues I am experiencing and it is an inexpensive and simple fix unless I am missing something.

Does anyone have any input or suggestions before I go down this rabbit hole?

Car has 184000km but engine only has about 12000km on it.

Thank you in advance.