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The mkiv Supra Owners Club

Weird missfire problem...Please help


garetheves

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...There was a fair amount of black smoke out of the back and even what looked like unburnt fuel so it may be a fueling issue, but also with it only really happening on WOT could it be a gapping issue with the plugs being new....Cheers, and thanks for being patient. Wonder if ill get an award for longest Technical thread. :)

 

I'm no expert, but everything I've read about spark plugs points to the fact that Densos (i seem to remember that's what you have) don't need gapping - they are pre-gapped. I presume you've confirmed that your plugs aren't too hot or too cold for your application.

 

If I had my way you'd have a an award, although I'd prefer you to have a fully functioning car again. Good luck at the Tuners.

 

Mike

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I'm no expert, but everything I've read about spark plugs points to the fact that Densos (i seem to remember that's what you have) don't need gapping - they are pre-gapped. I presume you've confirmed that your plugs aren't too hot or too cold for your application.

 

If I had my way you'd have a an award, although I'd prefer you to have a fully functioning car again. Good luck at the Tuners.

 

Mike

 

Yeah im using the same plugs that at least 2 other people are using with a T61 turbo and recommend. Almost tempted to splash out on a set of Iridiums though just to see if it makes a difference.

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well i must report that my problem seems to have been cured. so it was down to either or both o2 sensor / IAC not together properly.

still got another niggling problem, but i wont kill this thread with it.

 

thanks to all for all the input and ideas.

 

Rob

 

Glad to hear that mate...bastard. How did you check those 2 things. I take it you just had to buy a new O2 sensor and try it?

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yeah, i bought a new one off Nic, since mines old (shes done over 225k now) i thoguh i should get a new one just incase, and the old one did look knackered....

 

IAC, and yes you still have yours, just give it a look over, at first my gasket, which is metal wasn't on properly, then i put it back together wrong.

 

Rob

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heres a pic, gasket is between the 12mm bolts and the intake. it was originally checked by putting some fuel in a cup and, while shes running, pouring it a little at a time over the area and she used to increase in revs.

not sure id do it again. heat + fuel + me = not good!!!

 

Rob

t_intake.JPG

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Nic was doing a deal on £80 odd because of good exchange rates. only problem with it is that it takes at least 4 weeks.

 

i would do exactly as colsoop did. undo the 12mm bolts, top and bottom, 2 bolts, then unplug the air hose and pull the rubber fromthe inlet manifold. there is a little metal ring, looks like a trivial pursuit holder filled with orange segments, it comes out really easy. any trouble undo the top hose on the manifol and gently blow. the rubber sometimes gets bunged up with oil, as mine did, a bit of brake cleaner and TLC, be careful of the spring behind it, then put back together. (this is where i f**ked up originally, the ruuber must be flat side to the inlet and concave to the IAC unit).

 

then give her a try out!

 

Rob

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Ouch, 80 quid for an O2 sensor!! Bit of a Noob question but the O2 sensort is the one that goes in your downpipe isnt it. Didnt realise they would be that much.

 

Cheers for the info on the IAC, think ill give that a try ASAP. Got some engine degreaser im sure that would do the same job as the brake cleaner.

 

 

 

Nic was doing a deal on £80 odd because of good exchange rates. only problem with it is that it takes at least 4 weeks.

 

i would do exactly as colsoop did. undo the 12mm bolts, top and bottom, 2 bolts, then unplug the air hose and pull the rubber fromthe inlet manifold. there is a little metal ring, looks like a trivial pursuit holder filled with orange segments, it comes out really easy. any trouble undo the top hose on the manifol and gently blow. the rubber sometimes gets bunged up with oil, as mine did, a bit of brake cleaner and TLC, be careful of the spring behind it, then put back together. (this is where i f**ked up originally, the ruuber must be flat side to the inlet and concave to the IAC unit).

 

then give her a try out!

 

Rob

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carb cleaner does it for both. also brake parts cleaner, i think. ur just trying to get rid of the carbon build up on the interior of the o2 sensor and the oil on the inside of the rubber on the IAC.

 

So again engine degreaser would prob do a decent job on that. cool ill go give it a go before it goes dark.

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But im just thinking if by cleaning it it helps the problem a little then i would at least know it is that rather than buy a new one to find out it doesnt solve anything = 80 quid wasted.

 

 

Buy one from a breaker mate, should only be £5-10. I think it is not just a case of them getting dirty as such, they can develop other issues that cleaning alone might not solve.

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Nic was doing a deal on £80 odd because of good exchange rates. only problem with it is that it takes at least 4 weeks.

 

i would do exactly as colsoop did. undo the 12mm bolts, top and bottom, 2 bolts, then unplug the air hose and pull the rubber fromthe inlet manifold. there is a little metal ring, looks like a trivial pursuit holder filled with orange segments, it comes out really easy. any trouble undo the top hose on the manifol and gently blow. the rubber sometimes gets bunged up with oil, as mine did, a bit of brake cleaner and TLC, be careful of the spring behind it, then put back together. (this is where i f**ked up originally, the ruuber must be flat side to the inlet and concave to the IAC unit).

 

then give her a try out!

 

Rob

 

Ok just given mine a clean and putting back now. I put the little valve back in first dont i, then the rubber with the concave side facing the valve and the flat against the electrical part, or is it the other way round??

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No change after cleaning the IAC :(. Guess ill just have to wait for the O2 sensor to arrive and an Ignitor to come up for sale.

 

The IAC was bloody filthy though and very sticky with oil.

 

Before (bit blurred)

http://img239.imageshack.us/img239/221/dscf0006xp7.jpg

 

After

http://img239.imageshack.us/img239/8946/dscf0007zf3.jpg

http://img445.imageshack.us/img445/5056/dscf0008he9.jpg

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Ok just given mine a clean and putting back now. I put the little valve back in first dont i, then the rubber with the concave side facing the valve and the flat against the electrical part, or is it the other way round??

 

other way around the concave side must face TOWARDS the IAC unit, the flat side against the inlet manifold.

 

ur trying to increase the pressure against the rubber, ie smaller space...if you understand my meaning.

 

Rob

 

Jezzy dont suppose u got the TPS did you, what price are they??

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other way around the concave side must face TOWARDS the IAC unit, the flat side against the inlet manifold.

 

ur trying to increase the pressure against the rubber, ie smaller space...if you understand my meaning.

 

Rob

 

Jezzy dont suppose u got the TPS did you, what price are they??

 

Define "unit". Do you mean the actual valve (as you described it the Trivial Persuit piece) or do you mean the electrical plug that attaches to the manifold.

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concave side facing the electrical plug side, the flat side on the side with the actual valve...

 

Rob

 

Hmm put mine back in the wrong way then, Ive left the flat side facing the electrical unit and the concave side against the valve. Ill have another go tonight if i get chance before rugby.

 

Jezzy: Dont spose you have an Ignitor unit in stock do you??

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