E32 3 litre straight 6 misfire

[VirtualVince]

Hi. Was looking for some ideas to try that might resolve my engine misfire. I have a 1992 E32 3 litre straight six and I had taken it off the road for 2 years. Car was running perfect before, but since digging it back out (I missed driving it more than I realised) the engine has developed a misfire. I took the car for MOT and once on the ramp, the misfire cleared itself, but was intermittent on the drive home. I stripped the Distributor cap today and cleaned it. Also cleaned the Rotor Arm. Put it all back together and it still has a misfire. Any suggestions on what I should try next? Didn't know if this sounded like a common issue.

Thanks in advance for your help.

[shogun]

Maube you change distributor and rotor against new ones, the old one could have haircracks, difficult to see.
Next is remove all sparl plugs and check them, if there is a black one or wet one, that spark does not fire.
Check the ignition wires.
Nominal values for the ignition wires etc are in here https://www.bmwtechinfo.com/repair/main/
Did you change fuel or is that still in from 2 years ago? Check if the fuel tank has moisture inside, fuel will float on the water in the tank and the fuel pump could pump a mix of fuel and moisture to the engine.
Fuel filter I would also change after 2 years out of operation. Even fuel injectors could be clogged by old fuel.

[VirtualVince]

Thanks for your reply Shogan Will check the spark plugs later. Thanks also for the link.

[VirtualVince]

Started the car yesterday and it seemed to run very lumpy from cold. Also noticed it was 'hunting' while idling. Was about to pull the spark plug leads of individually, and the engine stopped misfiring. Maybe there is a different fault that is causing the misfire? I've not changed anything on the car since it was sat up 2 years ago, and it's still the same fuel.

[S1L1SC]

MAF sensor?
Might also have fixed itself if it was related to sitting that long.
(Clarification: Bad fuel got used up and runs fine now, something not lubricated and stuck getting lubricated and now working, etc...)

[biasvoltage]

Fuel does not remain stable over 2 years; I'd suggest draining as much as you can via the drain plug at the bottom of the tank on the right side. If it is an ethanol blended fuel it will undergo phase separation and there could be a bunch of water at the bottom of your tank; old fuel is bad news.

Keep in mind that it might not be an ignition misfire, it might be a plugged injector.

[VirtualVince]

Right. I know it has been some time, but I thought I would update you. I replaced the Distributor Cap and Rotor Arm for brand new ones. I also replaced the spark plugs. When I took the old plugs out, I noticed that 1-5 were fine, but #6 was looking a bit sooty. I put the new plugs in and the misfire was gone. Took the car out for a run, 25 minutes max and the misfire has returned. Took the plugs back out to check them and 1-4 were sooty, 5 and 6 were fine. I thought it must be Moore of a fuel pressure issue, so I fool the pump out (it's making a bit of a weird noise to be fair) checked it and all seemed fine, so I refitted it. Engine was still misfiring so I checked the plugs again, and #6 looked wet. Cleaned it up, put it back in and it's still misfiring but the plug is now clean after a run. I can only guess that the HT leads are part of the problem and #6 may be causing a weak spark? Other than that..... I am completely lost as to what is going on. I have a new fuel filter to go on the car now that fresh fuel is in it, but am I missing something obvious? Compression seems fine on #6 cylinder which has led me to think it's either an injector or HT lead that is causing the misfire.

[shogun]

I guess it is a problem with HT leads. Especially #6 is important, as that has the donut.
For example this M70 was only running on 10 cylinders, after he installed my new ignition wires, all 12 cylinders were working again, see the pics of the old ones http://www.bimmerboard.com/forums/posts/767718/
You can measure the HT leads, from plug at the distributor to plug at the spark plug 6 kOhm. On my M70 the angled plug going into the distributor has 1 kOhm, and the straight one going onto the spark plug has 5 kOhm

[VirtualVince]

Thanks for getting back to me Shogun. I did the multimeter tests on each lead (end to end) and this is the results I got.

HT lLead Resistance.

Plug Lead: Ohms:
1. 5.77
2. 6.02
3. 5.88
4. 5.83
5. 5.99
6. 5.85

Coil Lead:
2.13 Ohms

- - - Updated - - -

Also tried a different (known working) coil to make sure that wasn't the issue, but still misfired. Thanks for the link, will look at that shortly.

[shogun]

That looks all o.k. in case you mean Kohm and not Ohm , coil lead each plug, angled is 1 kOhm. so total 2 kohm and you measured 2.13.
Ever checked the fuel pressure? As a starter remove the FPR vacuum hose and sniff if there is fuel smells or fuel drops coming out.
Testing for a leaking, ruptured, fuel pressure regulator diaphragm
That is a good analysis. How to verify the cause of an intermittent long crank and a start/stall condition. No need to have the electronics as shown first (because we backyard mechanics do not have them anyway), just remove the vacuum hose and sniff if there is fuel smell or even fuel coming out. Watch for fuel. Takes over a minute that fuel is coming out of the port in this vid, diaphragm cracked. https://www.youtube.com/watch?v=AKtR_yF7bi8

Remove all plugs once more and check which one looks different in color, then you know which cylinder it might be.

Also a stomp test might give some hint.

[VirtualVince]

I recently put a new set of plugs in the car and it cured the misfire for about 20 minutes. The misfire returned and has remained ever since, so I fought another new set of plugs, put them in and the misfire was still there. I ran the car for a bit, took it for a blast and decided to take the plugs out and check their condition. 1-5 were all firing and the plugs looked fine. When I got to #6 (firewall end) I noticed the plug looked brand new with no signs of firing. The plug was dry with no smell of petrol on it, so I'm now guessing it's #6 injector?

Do you have a link on how to get them out as I've read various things online and I can't get my head round on the proper way to remove the injectors, fuel rail, and the wires in the plastic housing above the injectors.

[VirtualVince]

I recently put a new set of plugs in the car and it cured the misfire for about 20 minutes. The misfire returned and has remained ever since, so I bought another new set of plugs, put them in and the misfire was still there. I ran the car for a bit, took it for a blast and decided to take the plugs out and check their condition. 1-5 were all firing and the plugs looked fine. When I got to #6 (firewall end) I noticed the plug looked brand new with no signs of firing. The plug was dry with no smell of petrol on it, so I'm now guessing it's #6 injector?

Do you have a link on how to get them out as I've read various things online and I can't get my head round on the proper way to remove the injectors, fuel rail, and the wires in the plastic housing above the injectors.

Forgot to say that Diagnostics have been done on my car and it is showing no fault codes at all.