s14 missfire/hesitation 4000 rpm

[S14 ADAM]

Wondered if anyone can share their advice
Recently my 95 s14 has developed a strange missfire between 4000 - 5000rpm almost like hitting
Limiter And then it is fine
I have checked spark plugs and they seem OK also coil packs have been changed but no difference!
Has anyone does had this problem and resolved it?
Car seems fine either side of rev range
Thanks for any help or advice
Adam

[sx rider]

what exhaust are you running? Mine did that before decats were fitted.

[S14 ADAM]

I'm running a japspeed single silencer with decat fitted, I had this on before problem
Occurred

Thanks

[JuicyCarbonFX]

Mine does it at 17psi, its fine at 10psi, I am yet to investigate why its happening :/

[S14 ADAM]

I'm only on standard boost with a few mods but these were there before the problem

[doggy]

Check for the manifold/turbo leak. I constantly have problems with that, but from 3-4k rpm.

[S14 ADAM]

Thanks have to keep tightening up every so often but no leak at the moment

[Slip_n_slide]

As above, boost leak, or could be a problem with the MAF (or it might need a clean). Otherwise, plug it in to check the sensors as something could be throwing the timing out.

[S14 ADAM]

Thank you will keep investigating I guess cleaning AFM is next any advice appreciated

[Random Tim]

Boost leak, dirty MAF, hitting fuel cut if still on standard management, fuel pump on the way out

[S14 ADAM]

Its on its second walbro in a couple of years, just unscrewed AFM sensor and the contacts/thin wires look very sooty on one side
Any special tricks to cleaning without causing damage
Thanks

[Slip_n_slide]

Carb or brake cleaner in an aerosol can. Wynn's do a good one, just spray it on. Don't touch it with a brush or fingers though or it will break the sensors.

[silverzx]

I'd advise against brake cleaner, use carb cleaner.

Brake cleaner can leave a very fine film on it which'll cause more problems.

[S14 ADAM]

Thanks I will give it a try and see if it works

[S14 ADAM]

Problem sorted!!!!
It turned out to be AFM after a spray clean with some wd40 contact cleaner from home base
Being really care full, no missfires or any problems whatsoever.

A massive thank you to those who gave advice and recommendations!!

Thanks Adam

[Slip_n_slide]

*smug mode on

Whythankyou

*smug mode off

[JuicyCarbonFX]

I'll be very happy if that's what my problem is but it's not gonna stop me clutch slipping