V8i misfire shortly after startup

Hi my disco started up yesterday and as i drove off when i went to rev it it misfired and then took ages to get up to speed, after accelerating for a short time (at about 3500rpm)it sorted itself out and seemed to "lurch forward" suddenly and pick up speed, We started it again about an hour later and same again, I left it, started it up today and it misfired and stalled, i tried to start it and it just turned over for about 3-4 seconds without starting (it normally starts straight away) i left it for 5 seconds and it started ok, i went out for a drive and it just feels like the revs arent rising quite as quick as they should.

the only "tinkering" i had done previous was to liberally spray all the electrical connections/moving parts pulleys etc with the engine running on sunday and was wondering if some spray could have been sucked into the air intake (i have a K&N air filter also) and got into the mass airflo meter thingy as i did spray the headlamp connectors with the engine running and the air intake is right next to it? also the revs seem a little erratic and its iddling at about 400rpm instead of about 600rpm - what could be the possible causes and fixes? cheers

Ps it started running lumpy just on petrol about a week ago but now seems to do it on both petrol and gas.

PLEASE HELP!!!!!!!!!!!!!!

What electrical connections did you spray and what with?

unplug the MAF (mass air flow thingy) and see if the idle sorts itself out. If so clean the maf and put a paper filter in and lose the K&N as the oil from these can come off and upset up the maf

Might be worth cleaning all the whatever you've sprayed onto the pulleys off .. possibly alternator's slipping etc etc ...

hi guys sorry i havent got back sooner ive been really busy. Firstly i sprayed WD40 onto the hubs of the pulleys to quiet em down a little and stop em squeekin, i did try my best not to get the belt but obviously some went on it, - would it be noticable if the alternator was slipping eg visable or noisy?

Thinking about it it was running rough on petrol about a week before i sprayed everything (i was tryin to sort that out with the WD40) and when i left it running that day as i was sprayin it was runnin really sweet.

During the previous week of rough running on petrol as we filled up with LPG we got the mechanic to check the battery alternator etc and he said it was a very strong battery and was charging brilliantly.

also i sprayed the ignition coil spades and almost every wire i found, i didnt disconnect anything just gave it a little spray, i think i disconnected the MAF yesterday (the wiring from the square block on the air intake just after the airbox) and it was no different.

What i meant to say before was it BACKFIRED on starup and then runs rough, it seems a lot worst when the engines cold and almost sorts itself out after about 5-10 mins driving.

Ive replaced my HT leads about 8 months ago for performance silicone ones and i took the plugs out yesterday and cleaned em with a wire brush until they sparkled which seemed to make matters better but still not 100%

I seem to have made it run a little better on LPG and got the idling speed back up to norm by adjusting the little screw on the top of my LPG systems vapouriser (think ive made it richer) but its still not right by a long shot, after doin it my disco seemed to gain a new lease of life and as i took it for a test drive it hit 70 in 3rd very soon and it seemed great! (the engine was already warm) but the next morn the spluttery roughness was back.

Hope someone can make any sense from my ramlingscheers

Just a quick update - when i just started it up and switched it to LPG it was hunting in idle, when i took it out for a drive i found out that if i put the accelerator all the way down the problem was more noticable and it wouldnt go over 5000rpm, when the accelerator was only pressed 50% down the revs would rise right up to 6000rpm and the problem seemed to almost go away. (it was the same last week on petrol) When i got back from my 2 mile test drive it had stopped hunting in idle. hope this helps.

That sounds more like a manifold gasket leak. Or some kind of air leak on the intake side after the MAF.

andyb66 said:

That sounds more like a manifold gasket leak. Or some kind of air leak on the intake side after the MAF.

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well my friend i believe you may be right, my mate found a hole in part of the LPG system leading into the air inlet JUST AFTER the MAF, plugged it for now and WHOOPIE smooth running motor.

well bloody fingers crossed, i'll see how it starts from cold tomorrow

mrnice said:

well bloody fingers crossed, i'll see how it starts from cold tomorrow

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Well I assume no news is good news (fingers crossed )