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The mkiv Supra Owners Club

Intermittent missfire


jevansio

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My car has just started doing this tonight, sounded like a scooby, I knocked it into neutral & revved it & it was all right, back into gear & foot down a little & it was OK.

 

So I drove home & got it on the drive, it sounded a little ropey then too. So I went along each coilpack, removed it started the car to see if one made no difference & it sounded worse on every one, & better when they were all connected.

 

Funny this is after messing with the connectors it seems to have vanished. Is it possible one had a slight bad contact? All the coilpack connectors are brand new (under 2 months ago) and I bent the spring clip on each before installing to get a good connection. Anyone else cured a slight missfire by just unplugging them

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Mines not going anywhere if you want to borrow a set of packs bud

Cheers matey, might just do that, I'll see how it goes this week, I only put a fresh set of packs in when I went to 1.6 BAR, they weren't new but looked mint. Thing is everytime I get a problem like this my heart sinks & I automatically think "HG", I guess it's me being paranoid

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HG?? I hope not! Envy use 2bar plus no?

 

I have not heard of many sup headgaskets going.

 

I had a load misfire a white ago cause by a chaffed ht lead in the tunnel, it's probably either that or connectors/ign amp...?

I'm hoping it is electrical Mike, either a fouled plug or coilpack/connector.

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Mines was miss fireing and cutting out called out RAC who put it down to the main Coil HT leadpossibly faulty and he didnt like the idea of black tape on it.

 

Bought new from dealers £16 ok now so far. the old one was knackered had wires showing covered in tape ...

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Hey Jay mine was doing something similar at 1.4bar and Ryan noticed when checking the logs that the voltage was way down at high boost/RPM. So i bought an uprated alternator and it sorted it. If you've not already it might be worth checking it out.

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Mines was miss fireing and cutting out called out RAC who put it down to the main Coil HT leadpossibly faulty and he didnt like the idea of black tape on it.

 

Bought new from dealers £16 ok now so far. the old one was knackered had wires showing covered in tape ...

Cheers mate, mine's a coil per plug setup though :(

 

check all the wires going to coil packs they may be old brittle and cracked and shorting out especially right at front of head where they go into main plastic loom

Will check them over mate.

 

Hey Jay mine was doing something similar at 1.4bar and Ryan noticed when checking the logs that the voltage was way down at high boost/RPM. So i bought an uprated alternator and it sorted it. If you've not already it might be worth checking it out.

Cheers Rob, you've actually just reminded me of something that could have affected it in that area, I'm not saying though as it's rather embarrasing :)

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I suppose if anything it'll stop someone else being so stupid. I was making a cold airbox template for the car. I decided to disconnect the big wire going to the alternator, I knew I should really disconnect the battery before messing with stuff like this, but I was impatient. I took it off but accidentally caught it against something - the alternator housing I think, sparks went flying (I guess I had just shorted the battery out).

 

I put it back on carefully & started the car & it seemed fine so I forgot about it & carried on (disconnecting the battery this time :D)

 

Could that have affected anything?

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