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What is the cause of misfire

  • Valves

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  • Purge Valve

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Discussion Starter #1
Hello, everyone. Please help me find out why does my 2004 X5 N62 4.4 is misfiring.
At first, is started after I had to fill up with 87 gas instead of 93(the gas station did not have anything besides 87). It has been over a year since then.
I did replace all spark plugs, did not help. Found one coil was cracked - replaced, still misfiring. Replaced all injectors, no change. Replaced one PCV valve I assumed was bad, no change. Took it to a shop that specializes in engine diagnostics, they diagnosed cylinders 4 and 7 dead misfires and said my valvetronic shaft went bad, but when I started asking questions they become uncertain. Long story short I found that only coil packs needed to be replaced. Got much better but still misfiring. I did a smoke test: found a crack in evap hose that goes on top of bank 2 and connecting to intake. Taped it, no leaks. Another crack was on crankcase vent hose, also taped. No more leaks at the third smoke test. My air filter was bad too so I changed it. Autozone read my codes and besides random misfire they diagnosed bad purge valve. I ordered it and will replace in a few days. Going to check for wet spark plugs after that. But if all that does not help what do I check?
I have assumptions:
1. may valves be sticking closed? Note: at higher rpm the ride is smooth(that is why I assume valves may not be opening at idle and low rpm).
They aren't being washed with fuel as they were in earlier models. If so how do I clean them myself? I know people do sandblast but I can't.
2. may my fuel filter be the issue? However, fuel pressure was good when I changed my injectors.
3. may my secondary air valves be the issue(would there be a code for that or not)?

I must confess I knew about the purge valve for a year and did not change it. Shame on me. Will be too funny if it's replacement will solve my misfire.
All replies are much appreciated.
 

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Misfires

Hi Mike I have the M62 So not sure if it may be the same but I've had alot of the same issues and it continues to be the coils. One by one they go out...yes I know I should replace them all at once but wow she's an expensive beast. Anyway I saw a video once that helped quickly diagnose bad coils. With the engine running and the covers off remove the coils one by one. If the rpms change when it's pulled off it's good. If no change the coil is bad. You can check it by swapping with another coil to make sure but that's what it sounds like. Hope it helps. I'm in the process of replacing another couple coils, mass air flow sensor, expansion tank, and fuel filter. Fun stuff...next big project all the rubber in the suspension. I also suggest picking up a cheap Bluetooth OBDII reader, can't do everything you need but it does help chase down some things and you are able to check O2 sensors etc.
 

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Discussion Starter #3
Intricate03X5, I would be happy to find out coils is the issue. I am just waiting for the purge valve to arrive so that all known issues are addressed.
Actually, I just bought an Ediabas BMW Diagnostic Kit (Diagnostic Information System, Software Service Station, Technical Information System).
Should I see it is coils by swapping two of them I'll just change all of them.
The fuel filter is something I want to change after owning my X5 for over 2 years but do not know if the change is needed.
Fun stuff is that I am also changing the front suspension kit, but rubber itself is too much pressing out and in, I bought new control arms, Tie Rods, Sway Bar Links, and ball joints all for $138. Must be easier to change.
 

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It all started when a 1984 Porsche 944 was misfiring and a mechanic friend of mine suggested running a 20oz bottle of Techron through the tank, two tanksfull in a row. The engine smoothed out and never even hiccupped again.

I've since used it on two earlier BMWs, a 1990 F-150 that went over 360000 miles and my present2002 F-250 with 368K and my 2009 328i.

I don't stick to their recommendation for adding as I'm sure they just want more sold. It cleans the valves and how tightly they seal, cleans the injectors and anything else through which my fuel flows.
It's cheap insurance in my book.
 

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Discussion Starter #5
Appreciate the answer. I won't help in my case because in my 2004 N62 fuel is injected directly into the cylinder and does not wash the valves as it did in the earlier models. Unfortunately. But this is what manufacturers do nowadays - engineer with pre-planned weaknesses. All my injectors are new. While I still would like to clean the valves, it will be hard to do without even a garage (my case).
I used fuel system cleaners like 5 times in a row before I replaced injectors.
 

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Do a WWW search for DI engines carbon build up. It is even worse for turbo engines.
 

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Discussion Starter #7
Used Seafoam

Zulu95, appreciate the hint. I knew my X5 has the direct injection but I never googled it. Most results suggested spraying a can of Seafoam into the intake. And so I did. Lots and lots of smoke came out but I still have a misfire. Will check my spark plugs.

By the way, new purge valve arrived and replacing it changed nothing at all.
 

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Here's my standard reply for things to check on a random misfire code. You should clean your Mass AirFlow Sensor with the proper cleaner. Then check the hose (rubber housing) from the MAF to the throttle body for any cracks and leaks. The according part of the hose will usually hide a crack from you. This will suck in air and cause your misfire.
 

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Discussion Starter #9
Clean the Mass AirFlow Sensor

JeevesX5, thank you. I have done a smoke test 3 times. As the result, 2 cracks sealed. But they were on crankcase vent hose and on evap hose that connects to the intake.
But I will visually inspect the intake and clean the Mass AirFlow Sensor.
Misfire is not as noticeable as it was, I guess more than one issue contributed.
Hopefully, I will find and solve the remaining issues.
 

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Discussion Starter #10
Follow up on JeevesX5's suggestion to clean the Mass AirFlow Sensor: I did take it out, the sensor is clean, all pipes have no cracks. I also cleaned the throttle body. Service Engine Soon is still flashing at startup when RPM drops from 900 to idle. Started checking the spark plugs and cyl 7 was black again, not even 1000mi on it. But it wasn't wet. As if it was misfiring at idle but detonating on time at higher rpm. Does anybody know why my cyl 7 has wet spark plug even after changing the coil and the plug?
 

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Discussion Starter #11
Today I changed cylinder 7 ignition coil and I do not get the flashing "Service Engine Soon" at startup. However, I do get it flashing as soon as I start driving. Until my diagnostics kit arrives I can only be guessing. I assume I should change all ignition coils, not just one or two.
 

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Spraying Seafoam will not work from what I read. The cure for carbon build up is removal of the intake side, crushed walnut shell media blasting, vacuuming the residues out and then scraping any area of build up left after the media blasting + vacuuming again. Then you put the intake back together. Bavauto are now doing some sort of kit to assist owners to do the $2K dealer job.
The problem exists across all makes using DI or DI turbo engines. Some recommend that after you clean the intake you also change out the CCV systems to a "Catch Can" type to eliminate oil vapor in the intake system. Seems the old multi-port injection into the intake washed away the residue and kept this problem in check. I know I'll not be looking at any DI/DI & Turbo vehicles to replace the old X5.
 

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Discussion Starter #13
DIS showing me only CYL 7 has rough idle parameter far from 0. it is 7.5-8.5. And the only problem I have is CYL 7 misfire with CYL cutoff.
Changing coils does not help. I will try quick spark plug swap, but I don't think chances it will help are good.
According to the shop, diagnostics compression is good. If it was not I'd pour some fuel system cleaner in cyl 7 overnight.
The injector is also new same as all injectors.
Changing minimum valve parameter in INPA anywhere between 0.3 and 0.8 does not stop CYL 7 misfire with cutoff. Funny fact that my valves were set to 0.8 which is the max. Probably by the previous owner.
ANY SUGGESTIONS\ASSUMPTIONS WHAT SHOULD I DO WITH CYLINDER 7?

While diagnosing in DIS, I tried function to turn all possible engine functions ON\OFF for 30 sec. Turning secondary air helped to get engine work evenly, without shaking.
I also cleared mixture adjustment memory a few times but it only works well for a minute until CYL 7 cuts off. Same with deleting fault memory.
I assume if turning secondary air helped to get engine work evenly, I am not getting enough air, but if so why only one cylinder? Carbon buildup in that particular valve? I may use seafoam again.
 

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Seasfoam wont do much. Techron will but it has its limits.

If I was concerned on carbon build up Id do a techron treatment first but remember to change the fuel filter afterwards as it cleans out the entire fuel system and will lodge particles in the filter.

If that doesn't work lookup gm carbon cleaner used to fix chevy vortec engines with carbon buildup on the poppet valve vortec truck motors. That WILL remove all carbon. Isnt cheap but is 100% sure to clean it out.
 

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Discussion Starter #15
crowz, what is advertised to "clean out the entire fuel system" will not clean valves in DI engines. :tsk:
Only air from the intake passes there. That is why seafoam is applied through the intake when air flows around valves.
However, that won't clean well enough. Nutshell blasting will.:thumbup:
My question here is whether it is the carbon buildup that causes the misfire on one out of eight cylinders? :dunno:
 

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Carbon misfiring is from the space on the bottom of the head filling in with carbon deposits. This area can be cleaned with the correct additives. The gm additive I was referring to will clean it and it too can be added like seafoam is added but its normally fed thru the fuel pressure test port. When the gm product is used it is so effective you will SEE the chunks coming out the tail pipe. It has even been known to clog catalytic converters at times.

I have even used to fix bmw diesel engines that had buildup problems.

To know if it has a carbon problem I preferred to use a camera to look inside the cylinder thru the sparkplug hole. Very handy tool for that.
 

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Oh and the camera can be used to find buildup on the intake side that bmw had such an issue with and the adding via the intake feed like seafoam and letting it sit overnight broke those deposits up too. The biggest issue with removing it with the gm additive is the large pieces sometimes wedging in the intake valves. Not good.
 

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Discussion Starter #18
crowz, sounds very promising. The only thing that leaves me with a doubt is whether it is the buildup causing the misfire. I just spent a couple of hours diagnosing the car in DIS and INPA and saved some screenshots. For all the experienced guys out there, please take a look, any advice will help.:thumbup:
I have not changed all coils, but I did change a few, maybe I just need to change them all?
Injectors - new, spark plugs - new, compression - ok.
OR, maybe I should just fill misfiring cylinder with cleaning fluid overnight and then suck it back out? :dunno:
In my opinion, it as not the fuel pressure nor fuel filter, nor air because only one cylinder is misfiring badly and changing coils and spark plugs does not change that.
What do you think?
 

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There is a flaw in the guys test. Techron is meant to clean valves, lines, injectors etc.

The gm cleaner is for severe situations and isn't for cleaning lines etc its for removing deposits inside the cylinders/heads themselves. Stuff works great. Ive seen up to 3 inch chunks of carbon on the ground behind the vehicle after using it.
 
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