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[Gremlin]

Hi all
I know it’s probably been covered some where on the forum before. The question is I have a miss fire on start up from cold only by cold I mean over night or right through the day at work I’d say it is only one cylinder and the miss fire only last for around 15 to 20 seconds clears and then runs perfect. When warm car starts as normal and runs well.
I was told that the M44 engine dose not like the 4 pronged long life spark plugs that I put in it after I gave it its first service when I got her, so I decided to go back to the O.M. E Bosch plugs this has made no difference. The plugs I took out are perfect in every way burn wise light grey to brow. I’ve also been told it could be H.T leads but a set of these are not cheap and I’m reluctant to start changing things that are not the cause of the problem. It’s not showing any fault codes so I’m at a loss. Dose any one have any suggestions.

 

[TaffZee]

Sounds Like a dodgy coil pack to me, could be HT leads, But sounds like coil pack is about to fail.

 

[Sean d]

@Faheem a similar problem I believe

 

[t-tony]

Definitely sounds like a fault on the high tension circuit to me. Coil or cables. If cables are original I would go with them first.

Tony.

 

[Faheem]

Does it sound anything like this on a cold start?

View: https://youtu.be/6FGai2cl-dg

 

[NZ00Z3]

Have a good look for a vacuum leak (cracks or holes) in the rubber tubes on the inlet manifold and between the MAF and manifold.

 

[Gremlin]

Does it sound anything like this on a cold start?

View: https://youtu.be/6FGai2cl-dg

Sounds nothing like this and certainly dose not last as long as this short clip before it clears and runs smooth.

 

[t-tony]

Sounds nothing like this and certainly dose not last as long as this short clip before it clears and runs smooth.

Still think HT circuit. Can you upload a video of what you're experiencing ?

Tony.

 

[Gremlin]

Have a good look for a vacuum leak (cracks or holes) in the rubber tubes on the inlet manifold and between the MAF and manifold.

Will check this tomorrow as I’ve had a problem with this before but that just seem to make it run uneven rather than sound or feel like a miss fire. Thanks for input though.

 

[Faheem]

Probably not the same issue as I had then, I'll leave you with the experts then.

Mine used to have issues on a cold start- when the car was sat overnight. It started by a little bit of a rough idle / misfire which would clear in 10-20 seconds after which the car would run perfectly, however, over the space of a few months it progressively grew worse, until @t-tony successfully diagnosed this as sticking valves. Almost a year on and 3/4 oil changes and the issue has completely gone!

 

[Gremlin]

Still think HT circuit. Can you upload a video of what you're experiencing ?

Tony.

I will try but it’s got to be stone cold, once it’s run for about 20 to 30 seconds it’s clear until it’s stone cold again.

 

[t-tony]

I will try but it’s got to be stone cold, once it’s run for about 20 to 30 seconds it’s clear until it’s stone cold again.

May be a silly question but have you tried "wiggling" the HT leads with some Plastic lead pliers while the engine is running?

Tony.

ps. Probably you won't have some plastic lead pliers (I sometimes expect folks to have tools I have) but you can do the same using a wooden clothes peg, the type with a spring clip on them as long as the they grip the lead tightly.

 

[Faheem]

Sorry, last thing I want to add which may or may not help - this video was uploaded today by someone that I'm subscribed to and funnily enough it's about M44s and common issues around cold starting.

View: https://youtu.be/3r7jvpf66pQ


I would do what Tony says first but if no joy then the above may help

All the best

 

[Gremlin]

Not the plugs it’s HT leads least at moment this seems to have sorted the problem time will tell. I bought a nice set off eBay for £57 which compared to main dealers price at £236 was a no contest.