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The mkiv Supra Owners Club

Misfire under load


cainhead
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Hello,

 

Been having a few issues when boosting above 0.6/7 bar (Normally boosts fine to 1.0 bar). Almost like a misfire but its like a rapid fire judder with the needle on the boost gauge. The car will rev all the way through the rev range as long as I dont floor it. It gets worse the higher the gear which I would expect as the car builds more pressure in higher gears. The car is a single turbo. Has all new fuel lines and filter (this was happening before i installed these). It did clear up after i installed brand new coil packs and the clips are good, however its come back. The plugs are not that old but and i have had them out for clean up but not joy. Going to change them for new as first port of call, but just wondered if anyone could suggest any other checks to make.

 

Ive also checked the vacuum lines and cant seem to find any splits etc.

 

Cheers in advance.

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I see you have new fuel lines and filter but you mention nothing about a fuel pump, I have heard that a faulty pump can cause issues under load, do you have any starting problems?

 

Forgot to say the fuel pump is only a year old and it's uprated as I went single.

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What coil packs did you use if not Oem then they could still be a problem. When mine had a misfire it was usually at 5k revs but could feather it through to higher by not using full throttle. Mine was caused by a faulty coil pack.

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What coil packs did you use if not Oem then they could still be a problem. When mine had a misfire it was usually at 5k revs but could feather it through to higher by not using full throttle. Mine was caused by a faulty coil pack.

 

They were Whifbitz ones. I thought this would be best bet after OEM as Paul states these are used on their high power demo car and mines running no where near that. They only went in 1000 miles ago and they were fine until about two weeks ago.

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They were Whifbitz ones. I thought this would be best bet after OEM as Paul states these are used on their high power demo car and mines running no where near that. They only went in 1000 miles ago and they were fine until about two weeks ago.

 

The ones that failed on mine were the ones you currently have. See if you can borrow some Oem ones just to establish if they are the issue.

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Okay think I solved it. Tried the spark plugs from my other supra and it pulls really well all the way through the turbo. I thought i would try it with my Whifbitz coil packs first and no problems, which is reassuring as they are nearly new.

 

Just out of interest. Does anyone use the Bosch Platinum Iridium plugs, and if so what the exact model to use in a supra is. The ones i pulled out of my other supra were these but only had R6 and platinum iridium printed on the on the side of the plug

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Could just be me, but I avoid bosch plugs on 2J's. Always had issues with them, I use NGK on everything and always works

 

Like you I have always used NGK was just curious as hadn't seem much about platinum iridium plugs and was curious if they had any advantage.

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