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The mkiv Supra Owners Club

NA misfiring


scott87

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Right i posted a little while ago about my car bringing up the rear knock sensor error. Well today i decide im going to go and fix it so i go out to my car and off i go. The warning lights didnt come on on the dash and the car was fine for the first few hundred yards and then it became juddery and very lumpy. It is now doing this all the time. I changed the rear knock sensor and this has made no difference but the error code did not come back on the car.

 

I have checked the chambers 4 and 5 and niether of these had water in the them (i didnt have an allen key to take the cover off the check the others).

 

I have not lost any oil, not lost coolant nor are there any weird deposits on any of the filler caps.

 

The ignition system is all less than a year old. Any help would be great thanks. I have a video of it running which ill add to here too!

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I would check all the ports for water - does your bonnet vent have any kind of rain tray beneath it?

if it dosnt water (rain, water from washing) will go through that, onto the engine, then make its way down into the spark plug channels. Water in spark plug channels = lumpy horrid running car...

You can get an allen key set from Tesco's nowadays so dont even need to try and get to a motor factor before they close :)

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Check the inside of the dizzy cap for condensation. Dry the outside too and give the Dizzy cap and HT leads a blast of WD40.

 

What is it like when you rev it, is it still lumpy with a misfire?

 

That vid definitely sounds like a downed cylinder. Have you whipped the plugs out and inspected them? Check all your HT leads are on tight both on the plugs and dizzy and the King lead too. The igniter body needs a good earth too so clean up earth points too.

 

Any Codes of interest?

 

Lyndon.

Edited by Nodalmighty (see edit history)
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Rear knock sensor error is a timing related malfunction and your engine does sound as if it could be 'pinking' when blipped?

 

I have a very similar yet annoyingly intermittent fault which I suspect to be a faulty Throttle Position Sensor.

 

 

Right had a good look now the weather calmed down. The first 2 spark plug chambers were full of water. I have cleaned these out and the car seems much better, had a few blips still but i assume this is because i couldn't quite get all the water. Im hoping it is rain water as apposed to coolant.

 

I would imagine the knock sensor was triggered through excess vibration in the engine caused by a slight misfire? :blink: However this error is no longer present since installing a new sensor, but i did not know about the water in the chambers before changing the sensor so no idea if it were dodgy or excess vibration.

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No wonder you have a lot of water there considering type of bonnet lol

 

Very true. Although i didnt quite realise how lame the seal is on the ht leads. Im going to make a rain tray or change bonnet.

 

Also im pretty sure i need to change my timing belt too now, everything at once :(

Edited by scott87 (see edit history)
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Right had a good look now the weather calmed down. The first 2 spark plug chambers were full of water. I have cleaned these out and the car seems much better, had a few blips still but i assume this is because i couldn't quite get all the water.

 

This would be why i suggested to check this :-/ ...

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A decent polypropylene sheet would do the job fine. It's cheap as well. But it would be good to design something that was easily removable. I've seen some gash sheet metal designs under the bonnet.

 

Yer i'd want something light as the bonnet already weighs a ton!

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Its pretty light. I used it for my front splitter. I'm making another one, and using it as an undertray as my stock one is shot.

 

You can get different thicknesses, I used 4.5mm I will probably use the same for bonnet holes when I get a chance to design something attachable.

 

I've some left over from different projects. Measure it up and I'll send you some if you want?

 

I have the datasheet at work so I can check effects from temperature. It shouldn't be an issue but worth covering anyway.

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Its pretty light. I used it for my front splitter. I'm making another one, and using it as an undertray as my stock one is shot.

 

You can get different thicknesses, I used 4.5mm I will probably use the same for bonnet holes when I get a chance to design something attachable.

 

I've some left over from different projects. Measure it up and I'll send you some if you want?

 

I have the datasheet at work so I can check effects from temperature. It shouldn't be an issue but worth covering anyway.

 

Yer that would be great thanks :D

 

How would i go about attaching it, thats the bit ive not been able to get my head around. I thought that id need to make it "U" shape and then use an adhesive or somethinge?

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Well the easiest way is to use silicone. As long as it's on the inside of the bumper it should be fine.

 

Have a look online about the best way to attach it. I wouldn't say silicone was a method to recommend, but if it's causing problems with water it will solve the job. And also be easy to remove and won't damage the bonnet.

 

When I do mine, I'm going to place small studs into the bonnet so I can screw on the shields and just seal them with silicone around the edges. Problem with that is get it wrong and you will end up doing more damage.

 

I'm really unsure what to recommend, silicone would be the easiest and quickest solution though.

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