Hi.

I have a EVO 5 with a problem, my engine misfires randomly on idle but never on full throttle.
So, right now is my exhaust emissions really high.

The engine has been rebuilt has been driven about 2500 miles.

The last owner rebuild the engine because a head gasket failure, causing the head to warp.
So, a second hand head was bought and rebuilt:
Mild port carred out on inlet and exhaust
All valve seats and valve sealing edges recut and lapped.
Valve guides replaced with bronze items.
Cometic metal layer system head gasket and ARP head bolts fitted.
All lash adjusters replaced with 3mm uprated items.

The block was also refreshed with:
Cylinder bores gently honed.
Evolution VI connecting rods and pistons supplied then fitted with total seal piston rings.
ARP connecting rod bolts fitted.
All main and connecting rod bearings replaced with race specification items.
Full rotating assembly including rods, pistons, crank, flywheel and clutch plate all balanced.

When I bought the car the engine did not run perfect, I found out that one injector was faulty, it only flowed 350cc.
So I had them all replaced with 1000cc precision injectors and changed the fuel pump to a DeatschWerks DW200.

I have now mapped (LinkG4) the engine with E85 with good results (1.4 bar@377bhp).
The engine pulls real good without any misfire but as soon as it goes on idle it misfires randomly, it can misfire every five seconds to one minute apart.
It does not misfire when I start the engine, but maybe after 5 minutes.

I have done a compression test:
1: 12,3 bar
2: 11,8 bar
3: 11,9 bar
4: 12,5 bar

I also done a leak down test and all cylinder was about 5-10% leakage.
And the leakage come from the dipstick/crank case.
Is this much leakage?

I have new spark plugs, 0.6mm gap (NGK BCPR9ES)

I tried VAG coils to make sure that the ignition is ok, it is.

I have pressure tested the intake side, with slight leakage on the throttle axle but this is very very little.

No fuel leakage.

The leakage I had from the leak down test did come from the dipstick and crank case so this indicates piston rings, right?

But the engine does not smoke at all, neither on full throttle or on idle.

Is there something more I can do/test before take the head of?

 

I drove myself nuts with a misfire for a long time................
Then I found the injector resistor pack rusted beyond belief. One of the four wires was literally broken off. Inspect this, it can be found on the firewall. Box of four resistors.

 

^ picture? I have bad misfire right now switching from e85 back to pump gas.

 

I checked this, no visual damage on this.
But if this where damaged, would not my injectors not be working properly under load?

 

Quick resistance check with a multimeter will show you if they are good or not. Not sure the numbers off the top of my head but you are looking for four numbers that are very close. Any oddballs ( or in my case any that do not show any resistance and are therefor blown) will be very easy to spot.

 

Thanks, I will check this.

I will also check:

PVC, crank case ventilation
Crank angle sensor
Will try different spark plugs

 

Check for vacuum leaks as well.