Evo 4 need help misfire

[Dunkers1797]

Hi all this is my first evo after owning an impreza for a number of years and having trouble all ready.

I have a evo 4 jap import 96

Has a 3" stainless system from japan.

Air filter fitted with cold air feed

And a greddy profec B spec ll

Don't know what els has been done.

When I had it I looked through the boost controler at the peek it had been used which was 21 psi.
But I have been running at 14 psi and well it's no good.

10 psi 3rd gear WOT runs perfect.
11.5 psi 3rd gear WOT from 4000rpm it's stuttering misfiring and poping a little and well try to do 14 psi and you don't go anywhere fast.
The best peek I have has is 11 psi.

I have checked for air leaks, turbo pipes, coils, and all wires and can't find anything out of place.
I had a play with an focus st and lost this is how low I'm having to run it.

Also from cold to start it I have to use a tiny bit of throttle as it won't start otherwise after 40 secs it's ok but does hunt a tiny bit now and then. It has had the idal control valve changed but no change.

Any help welcome and anyone near Dudley welcome to look as I am really stuck now.

 

[DDS789]

Hi

I assume you've checked/changed the spark plugs? And checked their gap? They may need to be around .6mm

Also pretty sure one of the mods on the IV is to use a mappable ECU from a 5/6 (May only be a 6 as that is all I tend to see) I'm pretty sure there's some "max psi" the 4 ecu can do.

I'm not hugely up on the 4's just did a lot of research a few years back when I was looking to get one then ended up on a 5.

Double check for symptoms of crank walk too, just thinking it may possibly be signs of compression failure.

I'm no expert it's just advice

Simon Norton will be the main guy to contact, he's brilliant with everything!

He's on here under Simon@NTS

He does his work as a passion not for profit like some others

 

[RsvRob]

You may be experiencing fuel cut.
Ecu and injectors need changing to 5 or 6 ecu and 5-9 560 injectors.
Check out the sticky stage 1 mods in the tech section.
And yes check the plug's and gap to 0.55

 

[Dunkers1797]

Thanks for your help. Unsure of ecu that's on it. But mods are 3" turbo back exhaust, forge dump valve, boost controler, bigger front mount intercooler, and induction kit.

Checked plugs and all gapped correct. Been out in it today and boosts ok with no misfire for about 3 miles then starts to play up on WOT. I warm it up fully before I drive anywhere and took it up the road and seemed perfect and went like hell!! Then pottered about for about 2 miles and gave it wot again and started to splutter/ misfire. I'm 100% sure it not fuel cut as will go through it and then carry on. It's between 4500 and 5500rpm.

As said it will do 1.1 bar fine for about 3 miles then it's starts to fade with misfire after 3 or 4 miles and once I have used it for a while it gets a little worse

 

[DDS789]

So it sounds like something that happens when the car goes from operating temp to hot.

Again try new plugs, £15 from opie oils

The only time I've had trouble was when there was the slightest of corrosion on the end of the plugs and the coils had come lose, cleaned and tightened and all was fine.

RSV ROB knows his stuff too, so take notice

 

[Dunkers1797]

Will try plugs in the week. There is 1 new coil fitted so guessing the owner has been trying to fix it. I did check the number on the plgs but started with an f on the part number so thinking not the right plugs? Maybe can't take the heat?
Or could it be coil as it's only when hot and under boost. Never misses a beat otherwise

 

[DDS789]

Ideally you'll need NGK BPR8ES

 

[RsvRob]

Or the 7

 

[Dunkers1797]

Ye I thought that. Will change them wens and see how it goes. Cross my fingers as know coils ain't cheap

 

[DDS789]

Simon@NTS has my old ones with upgraded wires forsale bud.

They work perfectly.

Send him a PM