m50 hesitation/misfire

[kingkarl 136]

Over the last couple of weeks my m50b25 had started hesitating on cold starts. It felt as though it was running on 5 cylinders for 5-10 seconds. A blip of the throttle or shift into drive fixed the problem each time until...

On Saturday morning i faced the same routine. I generally feel a bit worse for ware on a Saturday too... so cut the old girl a bit of slack and gave her more time than usual to sort her sh*t out. Unfortunately a tap on the gas or shift into gear did nothing this time and the lump chugged away for a good 2-3 minutes with no improvement. Scared of damaging something I shut it down.

I broke the clip on one of the ignition coils a while back and replaced it with a second hand one which had been running perfectly since. At first I thought the second hand coil had crapped out. Nevermind though, the bloke I bought it off gave me a spare incase the first was dodgy so I chucked that in... Replacement coil #2 did nothing for the performance. So I got yet another off Brent yesterday.... that hasn't helped either.

I replaced the spark plugs within the last 5000km. I pulled a couple out today after work and they looked fine. No unusual carbon buildup etc. Of course that's not to say the ones I haven't check couldn't have some fouling...

Symptoms:

sometimes runs like sh*t when its cold... sometimes not

sometimes runs like sh*t when its hot... sometimes not

sometimes runs like sh*t when its idling... sometimes not

sometimes runs like sh*t at mid-high RPM... sometimes not

More often than not hesitates and misfires often under load.

I haven't replaced the fuel filter or had a look at the injectors since I've owned it (have racked up 15,000km since then). Possible cause?

I cleaned the ICV out about 4 months back but lubed it up with CRC before re-installing... which I have since heard is a dumb idea. Originally when the ICV needed a clean it didn't run anywhere near as bad as it does now so I don't believe this is the (main) cause.

The bentley service manual is little help.

My low IQ assessment of the problem is it is something ignition/fuel related. Or could it be something electronic or dodgy sensor?

Any tips would be muchas gracias

[polley 916]

can you pinpoint it to one specific cylinder been a problem?

[hybrid 1043]

Recheck the torque on the plugs ? sometimes they wiggle loose especially if you've replaced them recently. Has happened to be twice now. Love hate relationship with torque settings

[kingkarl 136]

Recheck the torque on the plugs ? sometimes they wiggle loose especially if you've replaced them recently. Has happened to be twice now. Love hate relationship with torque settings

Ahhh great idea - will do this when I get home. Cheers Josh

(I should really have bought a torque wrench by now)

can you pinpoint it to one specific cylinder been a problem?

I haven't been able to as yet. What's the best way to do it? It is dangerous to run the engine without the all the ignition leads plugged in, correct?

Edited February 5, 2014 by kingkarl

[*Glenn* 854]

Get it scanned to determine the fault correctly

[kingkarl 136]

Thanks Glenn,

I will do once I have exhausted my very limited talent.

[_ethrty-Andy_ 2132]

Thanks Glenn,

I will do once I have exhausted my very limited talent.

Glenn will probably tell you too, better to do it as a first step, so you dont end up either a) causing more problems, or introducing new fault codes later on when it gets scanned.

[adams202 1]

Recheck the torque on the plugs ? sometimes they wiggle loose especially if you've replaced them recently. Has happened to be twice now. Love hate relationship with torque settings

This - Happened to me a while after changing plugs. It was the first time I used a torque wrench to do them which made me laugh

[kingkarl 136]

This - Happened to me a while after changing plugs. It was the first time I used a torque wrench to do them which made me laugh

I tightened the plugs up last night... no improvement unfortunately.

I'll get it booked in next week to be scanned

[kingkarl 136]

Shite.

The DME is faulty. It's causing Injector #1 to only fire intermittently. On some level this makes me feel good because it is a relatively complicated issue I was never skilled enough to diagnose... so money wasn't wasted taking it to a pro today. But the issue seems more problematic than a faulty injector/lead/coil which I was hoping it was.

So I have a few options:

1 - Source a second hand DME. What I need to know is how many different configurations are there? Do I need one out of the exact same model as mine? Or is any m50b25 DME suitable. I probably need to do more research on this after work.

2 - Run my dodgy DME and splice injector #1 into injector #2. This is how it is configured now. Problem is it's only a bandaid fix for which puts more load on the system and could be likely to lead to further failure. Maybe I just do this and run it into the ground because........

3 - I can't really afford this sh*t to be happening each and every month. I shouldn't let myself be blinded by the sunk costs I've put into this car... especially considering it needs a lot more work going forward and the old tank isn't worth any more than 2k. I now live very close to work so perhaps I should just swap it for a *gasp*... moped.

I do love the bloody thing - even with its problems.

[lord_jagganath 421]

your part number is 12141744859 DME 3.1 ran from '90 to 92.... so it must be a non vanos one. shouldn't be to hard to find at the wreckers.

should be easy to get from 92 e36s ...

there's one in Hamilton http://www.pickapart.co.nz/stock.asp?yid=6

Edited February 19, 2014 by The Juggernaut

[antil33t 90]

Is the ECU repairable? not just a fuzzled track or a dry solder joint? i'd get a second hand one personally. Don't splice the injector wiring.