i've had a flat spot at 2500-3000 revs, gets worst towards the 3000 mark.
its never really been too bad, lately its been getting worst... starting to missfire

spark plugs seem ok'ish how ever there denso TRD IK24 'are these running too cold'
the engine isnt highly modified, just induction kit, manifold ect...

i've read that the rs200 uses IK20, should i try a IK22??

thanks in advance

i would switch to IK20 spark plugs, dont know anyone using ik24's?

No reason why you should have IK24s unless you have around 100bhp increase over standard. I would try IK22s

I agree with the above, I tried IK22's and had problems, mainly "bogging down" after idling and trying to take off. Put that down to plugs fouling because they were too cold. No real problems at higher revs though.

I have the same mods as you (check my sig) now on IK20's and all is OK with the car, so I would say go IK20 and try them.

Hope that helps.

Would IK20's be ok for a standard Altezza RS200?

yep

I have the same problem with mine at exactly the same revs, i cleaned the maf sensor which fully sorted out the top end flat spot, now i need to sort the bottom end...

I have no idea what plugs i have on at the mo, as i havent had the car very long and bit by bit trying to get it to my satisfaction

Would these plugs be ok for my standard Tezza? DENSO HKS IRIDIUM SPARK PLUGS IK20 X4 - £50 on Ebay.....

or can you point me to some better ones?

Cheers for the help

well yea, the standard plugs should be the ik20's
how ever with decent performance mods you may want to try ik22's

i'll try giving my sensor a clean see if it helps with my flap spot top end.

Hey, Other than changing the plugs get those coil packs checked as well, cheers.

Thanks for the advice,although i dont really know what a coil pack is? is this something i can check myself or only at a garage ?

Cheers

I'm sorry I taught you knew what they were. These are the little rectangular shape part (4) that goes on top of your spark plugs. I suggest you get them check by a professional (auto electrician)

I see, i know what they are now

Cheers

You have said that you have changed the air box assembly ,there has been a lot of problems when you change from the std factory air box assembly to a after market 1 .As the air going over the hot wire maf changes and you will get a flat spot .Put it back to std and try it and see if that gets rid of it

Ok changed the plugs to Denso Iridium IK20 and it seems to have improved it a little, but it's still a noticeable flat spot

Im going to take it into the garage next week and get them to run diagnostics and see if they can find the prob, i'll report back .

btw, Whitelabelboy have you had any joy in fixing your flat spot yet ?

Cheers

Do you have an induction kit fitted? If so that could be the problem. If you still have the standard airbox try put that back on to eliminate the induction kit as a cause of the problem. I might still have a spare airbox from my Deceased Altezza at home. Let me know if your interested in trying that.

@whitelabelboy. IK22's are only really needed for supercharged or turbo charged applications

Hi,

No i dont have induction kit, everthing on my Tezza is standard as far as i know... I changed the panel filter to a blitz filter, but this didnt make any difference...

Just in the last few days ive started to notice a good improvement in the flat spot and seems to be getting a little better day by day... I changed the plugs as i mentioned and also started using the new Maxol E5 petrol which says its 99 octane, this is my second full tank in 2 weeks so now should be pretty much all Maxol without other petrol mixed... Ive also been driving it quite hard hoping it would blow out the problems if there was a blockage or something...

Could the petrol be making the difference? could it be the ecu adjusting to the higher octane ?

It also seems smoother through the revs and if im not dreaming a little more powerful with this petrol, ill see how it is over the next week or so and give you guys an update...

Shop around on ebay coz I got mine for £35.00 quid from there , can't remember the guys name though but he was in the US

Running the car on E5 will make it run noticeably smoother. Try resetting your ecu and that may solve things quicker. Apexi filter offers the best filtration and airflow of any of the after market filters. HKS and Blitz provide rather poor filtration. Disconnect the airbox and clean the throttle body, gunk always builds up there just in front of the valve.

thanks for the advice i'll give it a shot