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The mkiv Supra Owners Club

straing missfire?


dr_jekyll

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Evening all. Over the winter i have done a few things to my car and as a result it had not been started for 2-3 months , i finished the car last week so i was delighted to take it out as soon as the snow had gone.

 

This is wer it confuses me , i took it easy for the first 100mikes to let everything oil up properly and the car was pefect never missed a beat. So then i decided to open the taps a bit . 1st gear was fine into second full throttle fine, third had a stutter but then pulled through m but as soon as i was in 4th on boost at WOT ther was a terrible missfire so i came back down to third, floored it and the same again , bad missfire, second and its perect.? this confused me .

 

the afr was reading 11s on boost , getting 8psi in second but 4thgear was only getting up to 5 psi during the missfire .

 

tomorrow im going to look at all the obviouse things such as dizzy cap , rotor arm. leads plugs. but is there any reason why it would only happen in 4th and 5th and itermittently in 3rd ???

Edited by dr_jekyll (see edit history)
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That'll be a boost related misfire, and it only happens in the higher gears because you don't make enough boost to show it up in 1st/2nd.

 

Plugs worn, gaps need sorting, a coil pack on its way out, or the connectors to them are dodgy. If your coil packs are breaking down the misfire will get worse quite quickly, to the point where you can barely run any boost.

 

-Ian

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its an na-t so i have a ditributor and rotor arm but thses look to be in good condition. the dizzy has only coverd about 2000 miles as have the ngk irridiums i have.

 

would it be anything to do with the car being stood for 2 moths and then only being started for a few minuets aday befor i stated using it again?

 

ill take it apart and inspect the plugs nand leads now ,

thanks

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after closer inspectio i have noticed that the plug wells on cylinder 1 and 2 have coolent in them 3and 4 are dry but 5 and 6 have oil in the plug well. im thinking this is due to a combination of the rocker cover gaskett leaking and the coolent pipe that cools the throttle body leaking .

 

would my syptoms be as a result of this ?

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Whether or not, they are both jobs that need jobbing.

Fix them, and clean up the H.T. components, then you will know for sure.

 

i know , i am ordering the rocker cover gasket, i just dont want to put it all back together and realised thers something obvious i could have done while i had it striped.

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