Freshly Built Rb26 Misfire

[33SOM]

Hi all,

Trying to find a misfire in my freshly rebuilt rb26.

The car misfires from idle to 3000rpm ish (haven't taken it higher)

What I have done to pinpoint the miss is

Unplug each coil pack (the exhaust note changes with each one unpluged)

Unplug each injector (same results as coil packs)

New plugs

New Crank angle sensor

Compression test showed all 6 cylinders even (148psi)

Sprayed carby cleaner around the place looking for vacuum leaks

Injectors have just been professionally cleaned

Unplugged the air flow meters. Car seems to idle smoother but misfires the same once I build revs up a little.

Not sure where to go from here?

Advice appreciated!!

[zoomzoom]

If the timing is good, do you have a way of checking AFRs?

[MJTru]

You should try changing the coils. Just as a process of illumination. Check injector plus make sure thats fine with a node light. Should be one of those. Last resort could be a broken ring. Need to do a leak down test. Wit broken ring its tricky. I had one years upon years ago but had compression.

[r32-25t]

were the velve seats machined? If so what valve springs were used? Were the seat pressures checked?

[Pridenjoy]

I would be checking ignition timing and cam timing.

[33SOM]

Cheers for the replies.

I should mention the issue started after it was assembled then went away. It had it's time on the dyno and has started playing up again.
The motor probably has about 50kms on it.

The Valve seats where cut. I'm using Tomei Type B springs.

Timing is spot on.

Going to try igniter and coils packs from a mate.

Cheers

[wld093]

Don't rule out coil pack loom.

[r32-25t]

Have the valve seat pressures checked, I would say you have valve float, seen it many times before with Japanese branded springs after having the seats cut

[33SOM]

What I don't understand is why I can't pinpoint the missing cylinder via unplugging the coil packs 1 by 1.

[Ben C34]

What ecu?

[33SOM]

Nistune

[zebra]

Is it lean as f**k?

[33SOM]

It's only just had a tune and ran fine afterwards for a couple minutes

[Ben C34]

What's happening to e mixtures when misfiring?

Did the tuner burn the changes to the board?

[r32-25t]

What I don't understand is why I can't pinpoint the missing cylinder via unplugging the coil packs 1 by 1.

cause of its valve springs it will be all cylinders

There was a thread only a month or so back where he had a missfire issue on a built engine and it turn out to be springs, also have seen it on about 3 other cars

[STATUS]

get it warm and pull the plugs. run a small mirror over each plug hole and see if it gets any condensation on it. report back

[nick81xd]

I put money on its running too much fuel pressure. Restrictive regulator

Edited June 11, 2015 by nick81xd

[33SOM]

Think so? It was tuned at 100psi... lol