I'm not deliberately abusing the Technical Help section with my old banger* :-) i have tried to make sure i've chipped in to help others where i can too. If i have any more problems after this i'll pollute one of the other forums with my woes :-)
Ok so i'm ready to book my MOT but i can hear a slight misfire at idle.
The car's had various vac leaks and poor idle since i got it (common mk4 petrol fault). The vac leaks are all cured (i think) - i can spray carb cleaner all over the intake components and no change in idle speed now. Just remembered i haven't checked the servo vac pipe.
Which leads me to spark. It's not a horrible misfire so weak spark? It seems to get better with a little throttle.
I've put new plugs in. I've tested the coil pack secondary windings resistances, all the same cyls 1 & 4, and 2 & 3. Can't test primary windings without removing the coil pack (access issue).
Bought new HT leads today but they're the wrong ones so will get them exchanged in the morning. Have run it tonight with the bonnet up, no visible sparks from the existing leads.
I've had to reset the fault codes (too much noise from all the battery disconnections) so it might trip a lamba fault tomorrow. Was thinking reading live values meantime for lambda - spark problem will be low lamba, air problem will be high, i think.
I think i've answered my own question now :-) ah well i've written it all now... Post!
* it hurts to call it what it is, a banger. I've put so much time and effort into it!
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Give it an Italian tune-up on the way and if it fails, take the hit and using the results diagnose the problems and cure them.
Fifty quid isn't too much in the running costs of a car today.
MOTs are a pain, I agonise before as well.
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beg borrow or steal a vacuum gauge
plumb it in and let the car idle
this will tell you instantly if engine is running at max efficiency
18 to 22 is perfect
anything outside look for leaks or poor compression
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BT - Haha it's going to end up that way :-)
BB - Many thanks for that. I didn't really know what use a vacuum guage was, now i've read up that is a cool bit of kit. My Grandpa will have one so i'll get a loan. Thanks for that, useful bit of knowledge.
I put new leads on but no real change - maybe revs a bit faster? Maybe making that up.
Ran with each lead disconnected and it was noticably worse for each one. Jeezo. :-) Vac test next, going to be a leak again.
If not i guess compression test next. Man i hope not.
Last edited by: Skoda on Wed 26 Jan 11 at 17:52
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Arrived home from work tonight at 10pm, package had been delivered, my vacuum gauge.
Hooked it up to the servo take off on the manifold. Supplied t-piece not fat enough so ran without the servo (car runs the same with servo connected, don't think the problems there).
Sitting more or less dead on 18 inches. Very mild occasional movement, maybe drop to ~17.9 then rest at 18, then maybe up to 18.1. Sounds a bit tappety, maybe slightly sticking valve?
Don't like the idea of throwing parts at it, but i read my tea leaves and it saw a new coil pack in the near future. First though it's getting a shot of STP petrol additive (which i think is just paraffin in an expensive bottle) and it will be roasty toasty by the time it arrives at Mr MOT Man's door at 1pm tomorrow.
:-(
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Didn't make that MOT appointment, had to phone up and cancel it. This wednesday i should be free. Fingers, toes and everything crossed.
I think that STP stuff worked, it's the only change i've made and it's now stopped misfiring. Glad i didn't buy the coil pack.
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Interesting that some snake oil appears to work. What is in it and what did it do I wonder?
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There's not much in it Espada, i looked up the safety data sheets and it says 80-90% petroleum distilates, further down it mentions the flash point etc. are the same as for kerosene.
80+% paraffin in an expensive bottle i'd guess.
Not sure where the cheapest place is to get paraffin, maybe garden centres for patio heaters? Certainly not petrol stations that's for sure!
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MOT this morning...
... guy knew i was nervous about emissions ...
... dragged it out forever, smiling the whole time ...
... picked up a pink sheet *heart sank* ...
Then wet himself with laughter and handed over a green sheet. Pass. First time, no advisories.
Don't know whether to call it a result or write to my MP and demand more stringent MOT testing :-)
Last edited by: Webmaster on Wed 2 Feb 11 at 12:14
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>>picked up a pink sheet *heart sank* ...
Then wet himself with laughter
Don't you love jokers. Tell him you've a neighbour whose just acquired a steam lorry that needs testing and he's bringing it in.
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Volkswagen Golf IV - 98 1.6 Misfire - bathtub tom
