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      01-21-2018, 02:38 PM   #1
arkie6
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2008 E90 N54 fuel injector issue?

I have a 2008 (build 11/2007) 335i base sedan that is basically stock. I bought the car used with ~70,000 miles a couple of years ago and it now has ~105,000 miles.

It has always had a bit of a stumble when doing a warm engine start. Cold engine starts seem fine, but if the engine is started after being warmed up and after setting 5 to 15 or so minutes, it really stumbles and struggles around 500 RPM for a few seconds, then the speed jumps up to around 1000 RPM and it smooths out, then it settles back down to a normal ~650 RPM. This condition is becoming more noticeable.

A month or so ago I had a cylinder #3 misfire that was isolated to the ignition coil (swapped coil #3 with #5 and the misfire moved to cylinder #5). I ordered a new set of 6 ignition coils. While waiting for parts I decided it was time to replace the leaking valve cover and oil filter housing gaskets, block off the PCV ports in the head, install an external PCV system with oil catch can, and clean / walnut blast the intake valves. The intake and valves had a pretty good layer of carbon buildup and I was hoping that was contributing to my rough idle. I got everything cleaned up and put back together and my rough idle on warm restart persists.

Previously I had an intermittent P0174 bank 2 system too lean code that would come in every few months or so. Now after the intake cleaning I'm getting both P0171 (bank 1 system too lean) and P0174 consistently. I thought initially the engine management system would just need to adapt to the new freer flowing intake tract without all of that carbon buildup, but after driving it a while, I'm not so sure that is the sole cause for the codes.

My code reader freeze frame data shows 700 RPM, fuel rail pressure 4810 kPa (~698 psi), 0% long term fuel trim and ~33% short term fuel trim for both bank 1 and 2 when P0171 and P0174 codes were set this morning.

I'm thinking about the only thing left is partially clogged and/or leaking fuel injectors. My injectors are index -07 and it appears the current version of the injectors is -12.

Is there anything else possibly causing this? I hate to spend ~$750 for 6 new 13-53-8-648-937 injectors and decoupling elements and that not fix the problem.

I have an OBD to USB BMW DCAN cable on order and hope to get the BMW tools software and cable up and running in the next week or so to see if there is anymore troubleshooting I can do before ordering the new injectors.

Thanks for any input.
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      01-25-2018, 02:44 PM   #2
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I'm looking forward to see what the experts have to say about this since I'm having the same problem.....I will change the low fuel pressure this weekend if that doesn't fix it I will precede with changing the bank 2 injectors with index 12.
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      01-25-2018, 02:52 PM   #3
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I have a new set of 6 index -12 injectors on order. Hopefully this weekend I will have the new injectors and INPA software and cable. Once I get them installed and coded, I will post my results.
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      01-25-2018, 09:00 PM   #4
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if you had leaky injectors (which I have had twice) you would get long starts when cold due to all the fuel sitting in the cylinder flooding it.

It is an easy diagnosis, just pull the spark plugs after the car has sat overnight. The cylinder with the leaky injector will have a wet plug that smells of fuel. The others will be dry and clean.

Bad design on BMW's part with these piezo fuel injectors. My 2007 335i has had 12 now. 6 done under warranty by Uncle BMW, and 6 I had to do. That is crazy. But keeping my fingers crossed, after so much trouble, it has been smooth sailing for the last couple of years, got 128,000 miles now. Hope to get many more years from it.
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      01-26-2018, 03:24 PM   #5
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My OBDLink reader and scanner is showing intermittent mis-fires on cylinder 1, 3, and 5. Mostly right after a warm restart when the stumbling is occurring. The car has new coils and nearly new spark plugs (all cleaned and inspected when new coils installed). The car runs good otherwise. Also, my fuel rail pressure is around 700 psi when the mis-fires occur and that is the pressure it normally maintains at idle and no load. I see it jump up around 2500 psi under moderate to heavy load. Are those fuel pressure values normal / expected?

My thinking is that it almost has to be the injectors leaking after shutdown. Starting a warm engine with too much fuel present will cause it to stumble and misfire. Overnight, the excess fuel in the cylinder either evaporates out of the intake or exhaust (whichever valves happen to be open) or the fuel leaks down past the piston rings as they cool and the end gap opens up.

I don't think my injectors are leaking to the point of flooding the cylinders yet. Hopefully I'm catching it soon enough to prevent any damage to the bottom end. My oil level stays pretty consistent dropping about a quart every 6,000 miles which is where I typically change it (I'm a bit over that right now as I want to get the injectors replaced before putting new oil in it). If the injectors were leaking significantly, I would expect to see the oil level rise or smell strong fuel smell at the oil filler cap which I do not smell with the engine running and the cap open.

My car has a build date of 11/2007 and the currently installed injectors are index -07. I bought the car with ~70,000 miles and do not have any history on it. Would these injectors be the originally installed injectors or have they been replaced sometime before I bought the car?

If it is not the injectors causing this stumble during warm restart, then what might it be? I'm still waiting on my OBD to USB cable.

Last edited by arkie6; 01-26-2018 at 03:32 PM.
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      01-26-2018, 03:39 PM   #6
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Oil level will not raise from leaking injector. However oil will degrade over time from mixing with fuel.

Your situation seems like the an injector issue.

If you continue with misfires or lean codes then maybe your cat is clogged.

I've had a really bad injector once and fuel was shooting out the exhaust on the ground. Car was not drivable.
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      01-26-2018, 07:06 PM   #7
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I just cold started mine up a while ago and immediately got out and watched the exhaust pipes as soon as it cranked (fired off quickly) and there was no smoke or anything other than exhaust coming out of the pipes.

Speaking of exhaust, is there any fix for the exhaust valve rattling? Mine rattles pretty good on startup when it is closed, but after it opens it is quiet. That rattling noise on startup is annoying.
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      01-26-2018, 09:40 PM   #8
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I pulled my plugs after it sat all night, that fuel did not evaporate, the plugs were wet and smelled like fuel. The high pressure line is indeed very high pressure. So your injectors will leak all night-- evaporation through the valves or not, your plugs will be wet.
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      01-27-2018, 11:00 PM   #9
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I got the new index 12 injectors installed today. Pretty simple task. No issues getting the old injectors out. I just pulled them out with a pair of channel locks gripping the nut below the fuel line threads and wiggled a bit and they came right out. I've got the coding information written on a piece of paper. I tried to match as close as possible the flow rate on the new injector with the removed injector. My INPA cable for coding the injectors hasn't come in yet (USPS mis-shipped it, but it should be here first of next week). I haven't started the car yet, but is there any reason I couldn't start it up and let run it long enough to check for leaks and see if the warm restart stumble has been resolved?
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      01-29-2018, 12:06 AM   #10
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I started it up today and the new injectors appear to have corrected the warm start idle stutter and stumble. I did about a half dozen or more warm starts and every time the idle immediately jumps up to 800-900 RPM and smoothly drops back down to ~650 RPM. I drove it ~10 miles to warm it up for an oil change and there were no check engine lights, no pending codes on my OBD scanner, and no cylinder misfire counts on any of the cylinders. After the oil change I drove it about 20 miles and filled it up with gas. No issues whatsoever. Smooth idle, plenty of power, and by the onboard fuel mileage indicator, it appears to be getting better MPG, but this may be due to the fact that I haven't coded the injectors yet. Previously on a trip like this I would be showing long term fuel trim = 0% and short term fuel trim = +33%. On this trip with the new injectors I still had long term fuel trim = 0%, but short term fuel trim was -3% on one bank and -5% on the other bank. Anyway, it appears to be running good with the new injectors. I am going to wait to drive it hard or any distance until I get the injectors coded.
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      01-29-2018, 05:42 AM   #11
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Not sure you need to worry about coding. My indie tells me the engine re-learns the new injectors fairly quickly. When I changed my injectors, I found that several of them had been changed under a recall. The dealer hadn't coded them in, but they ran fine...
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      01-29-2018, 08:43 AM   #12
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If anyone else is thinking about ordering these injectors, I just got a notice in my email that BMW of Corpus Cristy lowered the price on the new injectors by $29 each on their ebay listing. Now they are $104.39 each which is about $10 less than I paid for them. Don't forget the decoupling elements. You don't need to order seals as they are included with the new injectors under the tip cap.

Here is the ebay link to the new injectors at BMW of CC:

https://www.ebay.com/itm/282775162625
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      01-29-2018, 03:02 PM   #13
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Quote:
Originally Posted by Phil325i View Post
Not sure you need to worry about coding. My indie tells me the engine re-learns the new injectors fairly quickly. When I changed my injectors, I found that several of them had been changed under a recall. The dealer hadn't coded them in, but they ran fine...
I'm not sure how the engine could learn what individual injectors are doing since cylinders #1, #2, and #3 (bank 1) output is monitored by lambda sensor #1 and cylinders #4, #5, and #6 (bank 2) output is monitored by lambda sensor #2. If the DME sees bank 1 as too lean, it could make an adjustment to increase the fuel in cylinders #1, #2, and #3, but I don't see how it can make adjustments that would affect only cylinder #1 for example. It is probably "good enough" right now since there are no active or pending codes and no misfire counts, and it is definitely better than it was before I changed the injectors, but I doubt that it is as optimized or as efficient as it could be if the DME knew the exact measured power/flow rate of each individual injector and could adjust accordingly. Given the short term fuel trim numbers I'm seeing, I'm probably within 5% of optimum. But 5% is about 15 HP or 1 MPG.
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      02-11-2018, 11:17 PM   #14
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I finally got my fuel injector energy and flow rates coded. Car is running, starting, and idling good now. Didn't really notice any difference in power or smoothness, but my new injectors weren't that far out from the previously installed injectors. I'm curious to see if my MPG improves with these new injectors and walnut blasting of the intake. After verifying no leaks, I have re-installed all of my under hood engine and cowl covers which makes a big difference in the noise from the engine.
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      02-12-2018, 09:23 AM   #15
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Quote:
Originally Posted by arkie6 View Post
I finally got my fuel injector energy and flow rates coded. Car is running, starting, and idling good now. Didn't really notice any difference in power or smoothness, but my new injectors weren't that far out from the previously installed injectors. I'm curious to see if my MPG improves with these new injectors and walnut blasting of the intake. After verifying no leaks, I have re-installed all of my under hood engine and cowl covers which makes a big difference in the noise from the engine.
Glad to hear you resolved this and that things are good now.

Thanks for the update.
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      02-27-2018, 01:08 AM   #16
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I noticed something interesting tonight after filling up the gas tank and checking my fuel mileage.

Right after I got the car a few years ago I would check the actual fuel mileage against the mileage indicated on the computer. I would typically get 6% to 7% better actual gas mileage than indicated on the computer. Over the past 6 months or so prior to changing the fuel injectors, I was seeing 8% to 10% better MPG than indicated on the computer.

Tonight when I filled up and calculated fuel mileage, actual MPG almost exactly matched the computer indicated fuel mileage (calculated was 24.8 MPG, computer indicated was 25.0 MPG). So what changed?

After I installed the new fuel injectors, I also wrote down the energy and flow rates of the old injectors. Before I coded in the new injectors I verified the values in the computer matched the old injector energy and flow rates.

As stated above, I was getting intermittent lean condition codes on bank 2 that were getting more frequent and also started getting lean condition codes on bank 1. What I suspect was happening is that the old injectors were partially clogged and getting worse and they weren't spraying the volume of fuel the computer was assuming and this was not only causing the lean condition, but also affecting the computer MPG calculation.

Just throwing that out there for anyone else having similar symptoms.
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      07-07-2018, 01:04 AM   #17
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arkie6,

thanks for the post and follow up. I have an 08 335i 99k. I am expeiencing lean condition and misfire. trim went way high and gas mileage tanked. I am hoping swapping the injectors can mitegate these issue. Your example has helped.

Have the new injectors been holding up so far?
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      07-07-2018, 01:16 PM   #18
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Quote:
Originally Posted by adrken2008 View Post
Have the new injectors been holding up so far?
So far, so good. No issues.
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