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Missing At Hi Rpm

_8OO5TED_

By _8OO5TED_,
in Engines & Forced Induction

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_8OO5TED_ Mentor

_8OO5TED_

Posted
Posted (edited)

Hey guys,

I just fitted brand new NGK Iridiums to my 1993 RB25DET. The car has only a cat back exhaust, BOV and a pod filter (stock ecu/boost).

I had the new plugs fitted I thought it missed from dodgy plugs and when the old ones were pulled out they looked pretty average so I had the NGKs fitted.

After doing this the car still misses when it comes on boost or under full load. The guy who fitted the plugs also adjusted my idle rpm as he thought it idled too high, but this was only because the car was freezing cold. I presume this is done by adjusting the timing?

Could this have played a part in the car still missing with fresh plugs?

Cheers!

Matt

Edited by _8OO5TED_
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dajorad Rookie

dajorad

Posted
Posted
Hey guys,

I just fitted brand new NGK Iridiums to my 1993 RB25DET. The car has only a cat back exhaust, BOV and a pod filter (stock ecu/boost).

I had the new plugs fitted I thought it missed from dodgy plugs and when the old ones were pulled out they looked pretty average so I had the NGKs fitted.

After doing this the car still misses when it comes on boost or under full load. The guy who fitted the plugs also adjusted my idle rpm as he thought it idled too high, but this was only because the car was freezing cold. I presume this is done by adjusting the timing?

Could this have played a part in the car still missing with fresh plugs?

Cheers!

Matt

What plug gap did you use? The standard gap is 1.1 mm but this can be too large. I had the same problem when my plugs were changed. had to re-gap to 0.8 mm and then was OK.

Also check coil packs.

See http://www.skylinesaustralia.com/forums/in...lug+gap+rb25det

rob82 Mentor

rob82

Posted
Posted

He may have missed that the throttle was not closed when he checked the timing. To set the static timing the ECU must register that the throttle is closed and that the engine is up to temp ie above 80deg. Once these two conditions are set that timing should be 15 deg. Now if he adjusted the timing with the TPS not registering closed throttle the timing numbers shown on the timing gun would be around 18 - 20 deg in which case he may have retarded the timing 3deg which is more than enough to cause a miss.

If he thought it was idleing to high he should have adjust the IAC bypass valve not the timing. Alot of people dont realise that retarded ignition timing can cause a miss fire event.

RB30-POWER Mentor

RB30-POWER

Posted
Posted

Your mechanic sounds like a dick!

Take it to someone that knows RB engines.

If your car is missing with 0.8mm gap, you will more then likely have a dud coil. (Hairline crack from heat, allowing spark energy to escape)

For standard boost, you shouldn't even need 0.8mm gap. But it will prove if its the spark or not.

If you are running more then standard boost, it could even be the infamous Nissan "Rich and Retard" happening. This is where the ecu uses parts of the maps that are very very conservative with timing and very heavy with fuel. This might be what your feeling as well.

Good Luck!

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