Fuel issue ? Injector issue ? Help.

[Lukeiswho]

This is her, please help.

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Hello all,

The car seems to be running fine, though, since I work from home, it doesn't get to stretch it's legs as much as it should. But recently I've taken a few ~30 mile journeys and noticed an odd thing. Occasionally, at freeway speeds, I notice what FEELS like a short, strong gust of wind hitting the car at the front. It's almost like taking your foot slightly off the accelerator. It only lasts about 1 second, and happens maybe 2 or 3 times on a journey. It's not a total loss of power, it's just like the revs go down slightly. But I don't hear anything out of place... the engine, from what I can hear, is carrying on at the same pitch. There is no coughing or spluttering. I suppose I could just be hyper aware of it... or maybe there IS wind... but I've only noticed it recently, and I live in Phoenix, which is not known for it's strong wind.

Is it possible it's an intermittent fuel leak, or injector issue? A misfire? Bad spark plug? I'm not THAT handy with newer cars, but I'm happy to stick my head under the bonnet and check for dried out rubber lines or check spark plugs... but figured I'd ask here first.

Full disclosure: the previous owner removed the muffler, but kept it, and I had it put back on. Also, I had a scan of the car done recently with a code for a bad "Evap leak detection pump", which surprisingly, I was told by the head tech of the local BMW shop, I could ignore as long as the light on my dash doesn't annoy me. Don't know if either of those could be possible contributors, but there they are.

Thanks!

[stupot67]

Hi,

Could be lot's of things, but I would put a fueling issue quite low down the list.

I take it there are no fault lights on the dash, but that doesn't mean there aren't any pending codes, you really need to get a good code reader and look for pending codes.

For starers I would be looking at the vanos solenoids (Easy to remove and clean/replace) and the eccentric cam position sensor (Removes the plastic valve cover, there is a round electrical connector towards the front of the engine, pull this out and look for signs of oil - A sure sign the sensor is failing, these sensors very rarely trigger a fault code, but have a significant effect on the way the engine runs)

Good luck!

Stu.

[MACK]

Unfortunately this could be a number of things, a large number at that. I would scan it and see if there's anything what I know as "soft coded" others call it "pending codes" in there to give you a clue. Otherwise with intermittent faults, particularly ones as intermittent as this its a case of swapping bits out in a trial and error fashion.
Honestly, unless there's a code I would probably leave it till it presents itself more frequently/dramatically. I know its annoying and it would send my OCD mad but most people dont have the software to scan it for free and certainly don't have a "spare" car to swap bits with on a trail basis so you would be buy bits and that gets very expensive very quickly.

[Chris1981]

I think Stu has the right idea on where to start, my 3.0 si coupe had a bit of hesitation during acceleration at times but she eventually threw an engine light and error code on camshaft/crankshaft correlation on the exhaust vanos (or words to that effect!)... changed both vanos solenoids to be on the safe side and it's been good as gold since with no codes returning! Think i'll check out the condition of my eccentric camshaft position sensor now too, cheers for the tips Stu!

Changing solenoids is a pretty simple job, you'll find plenty of how to's on 'the google'!

[Lukeiswho]

Thanks guys, will investigate!

[Lukeiswho]

Well, not an entirely uneventful endeavor... I pulled the vanos solenoid, which "looked ok" to my untrained eye... I gave it a wipe down and sprayed it out with some air. Then I checked the eccentric cam position sensor which also looked mostly fine, but there was just the least little bit of moisture under the cap, which had to be oil. It didn't appear to be touching any of the terminals, it was just on the outside rim, but I cleaned it out with a q-tip.

Then to the big obvious thing... there was oil leaking from my filler cap. I really don't know why this was happening. All I can guess is the last person to fill it up, BMW tech when I recently had the gasket changed, didn't click it all the way down? Or something potentially more troubling and worrisome. But I cleaned it the best I could, verified no oil made it into the ignition coil or down to the spark plug, and made sure the cap sealed up tight. Will put it through it's paces this weekend and see if any of that had an effect.

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[Chris1981]

That's a bit of a mess!

If you're lucky it is just a bad aim when trying to fill the engine with oil, however a blocked CCV system will not allow air to escape the valve cover and pressure to build inside it this can then cause oil to leak from any weak points, filler cap and gasket being the weak points. Is there a leak from the gasket to the cylinder head too?

https://www.yourmechanic.com/article/sy ... -pcv-valve

[Lukeiswho]

Still happening today, just as frequently. Have a ~300mi trip coming up... may not be taking the Z if I don't get this sorted.

Checked the oil level (on the dash) and it was near the middle. Service is due in 2000mi or so.

There doesn't appear to be any other leaks. Replacing that gasket was actually the last thing I had serviced. Will look into the CCV system.

[Lukeiswho]

I've driven it the past few days, the issue is still there, but still pretty minor. I also stuck my head under the hood again. I took the cover off the engine and looked for new oil leakage, and didn't notice any. So that's good. When I checked the oil, it still says OK and is around half on the digital gauge. I bought some oil just to have in the car with me.

I also went down to the local part shop and they plugged in to check for codes, and I only got the same code I had before about the "Evap leak detection pump"

I'm planning to drive around 300 miles on Tuesday (then back again in a week) and I'm wondering if I should worry about taking this car or not. Does anyone have any strong opinions on this?