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The mkiv Supra Owners Club

Misfiring / buffeting


FilS004
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Hi all,

 

I have a problem with my poor Supe. When I get to approximately 8psi / 0.5-6 bar, I get what feels like it is only firing on 4 cylinders, but it sounds like a buffeting noise or some turbo problem. I get no misfire what so ever when it is under below the 8psi. I have replaced all of the plugs and packs and the rubbish connectors on the top of them and all of the vacuum pipes. I have tried running with an open boost controller, which should be using the ECU as normal and I have even bypassed the boost controller solenoid to make sure that it wasn't that sticking or something.

 

Have I bu**ered my turbos?

 

Cheers anyone that can help me or point me in the right direction... Fil

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They are iridium plugs, so the gap is set. When I first installed the new plugs and packs, it was fantastic, but it started misfiring (or that I thought was misfiring) at full load as if one cylinder was not working, then it got worse, so I changed all of the crappy plastic connectors on the top of the packs, as they were so brittle. But it hasn't made any difference.

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They are iridium plugs, so the gap is set. When I first installed the new plugs and packs, it was fantastic, but it started misfiring (or that I thought was misfiring) at full load as if one cylinder was not working, then it got worse, so I changed all of the crappy plastic connectors on the top of the packs, as they were so brittle. But it hasn't made any difference.

 

What is the spark plug code?

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It doesn't seem to say on the advert what the plug code is, can you pull one of them and read the code off the side? if you have the wrong heat range plugs fitted it could be the cause of the misfire.

 

When did you first start to have problems? was it playing up before fitting the spark plugs? what's the spec of the car any other performance modifications?

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I will get a plug out an let you know. it was running great when I first installed them, it just got worse after 5 or 6 full blasts of 10 miles or so. I have a 200 cat instead of the original 2 cats. The exhaust is 80mm straight through. I have a blowoff valve, all of the vacuum pipes are new silcone pipes with no folds or anything in them. Oh and a gizzmo boost controller, which fixed a problem that I used to have on full load at around 140mph, especially when it was going uphill so there was alot of load on it.

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I suppose that I can remove and replace all of the plugs and packs, just to see if there is something funny going on there. I should imagine that there will be oil on a plug that isn't working correctly eh?

 

I thought you'd already replaced the coil packs and plugs?

 

I had a misfire like this when a coil pack was breaking down, and it got worse and worse, to the point that I couldn't go on boost at all. I also have had a misfire above 0.8bar when it was 100% fine below that, and it was because my E-Manage was set to 5v ignition rather than 12v.

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I guess it is deffo a plug problem, see the pic

 

Yes, I replaced all of the packs and plugs, I meant to undo them and put them back in just to have a look. (not get new ones again)

 

Thanks Ian C, I will look at some colder grades of plugs and see how I get on with them.

IMAG0209.jpg

Edited by FilS004 (see edit history)
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Where's the ground electrode gone, and what damage has it done? Ceramic, (or any other), turbos won't like that "up `em" ;)

 

The buffeting you describe is often from a turbo with a damaged compressor or turbine wheel that pumps enough air to operate, but at an imbalance to its partner.

 

It looks like it has been burnt away actually, so I don't think that it has gone anywhere.

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It looks like it has been burnt away actually, so I don't think that it has gone anywhere.

 

Something's very wrong if it's managed to melt the negative electrode. On the pic you posted is there also a chip out of the white ceramic insulator?

 

If the electrode has broken away it could have made a right mess inside, you really need to get a bore scope down the plug hole to see if there's any damage been done and also check the condition of the turbine wheels.

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hmmm.. .doesn't sound very nice then. I will checkout the plug in more detail when I take it out again to see if it has been melted off, or that it has broken off. I think that the 'chip' in the ceramic is just bad lighting on the photograph.

 

Got a borescope, so I will give the inside a good check over aswell.

Edited by FilS004 (see edit history)
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Changed the set of plugs to a grade 8 so they are cooler running I think, whatever that means, and it runs great again. So no probs with the turbo or anything. The piece of plug either burnt off, or if it fell off, it must have gone through everything without touching anything. Don't know and don't care now. I will send the set of plugs back to NGK, to see what they say about it.

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