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The mkiv Supra Owners Club

Missfire


miko_supra

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Other bits to check:

 

Is the Ignitor grounded well? Check with a multimeter

 

When the missfire happens does the rev counter go abit crazy i.e jump around 1k as this normally points at a Crank sensor issue.

 

My bet is on the coil pack pins though.

 

The car revs through fine, it just feels under powered and you can hear the engine running badly out of the exhaust, it's very rapid, sounds like its farting. When i look at the boost gauge it is peaking at about 13 psi (usually 18psi) and the needle is juddering between 12 and 13psi. The car will go all the way to the top of the revs also.

 

I started up the car a moment ago and using a dentist mirror i checked the coil packs to see if they were arcing at all.

 

When i changed the clips i also adjusted the little flap of metal in the connectors to get a better contact too.

 

I'm going to get the multimeter out tomorrow and start checking earths and the resistances on all coil packs as well as sensors.

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I have just done a compression test on the engine... (PSI)

 

1)191

2)185

3)188

4)191

5)190

6)162

 

Thats 15% difference between cylinder 1

 

I tested the 6th cylinder with some oil in it and i got 227.8psi. Tested number 1 cylinder with the same and i got 250psi. Which now equals an 8% difference.

 

I did a boroscope on the cylinders before xmas and the valves all look fine. Im going to take it to a garage next week to get a leak down test done.

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I have just done a compression test on the engine... (PSI)

 

1)191

2)185

3)188

4)191

5)190

6)162

 

Thats 15% difference between cylinder 1

 

I tested the 6th cylinder with some oil in it and i got 227.8psi. Tested number 1 cylinder with the same and i got 250psi. Which now equals an 8% difference.

 

I did a boroscope on the cylinders before xmas and the valves all look fine. Im going to take it to a garage next week to get a leak down test done.

 

After speaking to a few friends it seems that this wont be the cause of a misfire, although i am going to investigate it some more. When my new multimeter arrives im gonna do some more checks for the misfire

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  • 3 weeks later...

YES YES YES YES YES!!!!! It's fixed hoorah! i've had a enjoyfull morning of loosing traction at 70mph on those greasy roads. She boosts fine now all the way up to 1.2 Bar without missing a beat :D

 

Ok what i did... I inspected the coil packs again, checked their resistances and they were all covered in tiny cracks so i filled the cracks with araldite, let it dry and then smeared an electrical insulating gel around the stem of the packs. Problem fixed! the sparks must have been shorting onto the block due to the cracks. I had checked at night time before to see if i could see any sparks but could not. But oh well she drives nicely now :D

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YES YES YES YES YES!!!!! It's fixed hoorah! i've had a enjoyfull morning of loosing traction at 70mph on those greasy roads. She boosts fine now all the way up to 1.2 Bar without missing a beat :D

 

Ok what i did... I inspected the coil packs again, checked their resistances and they were all covered in tiny cracks so i filled the cracks with araldite, let it dry and then smeared an electrical insulating gel around the stem of the packs. Problem fixed! the sparks must have been shorting onto the block due to the cracks. I had checked at night time before to see if i could see any sparks but could not. But oh well she drives nicely now :D

 

Nice 1! Good find that. ;)

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