Intermittent misfiring on rb25det

[Poketmony33]

Intermittent misfiring on rb25det

My r33 skyline has recently started intermittently  misfiring on idle and while driving. 

Spark plugs are new, new yellow jacket coil packs, replaced the o2 sensor, and cleaned the maf several times and a fuel system flush has been performed 

the misfire doesn't sound to be on anyone cylinder. when it does misfire white smoke comes from the exhaust and the coolant level has been going down.

Could the turbo be leaking coolant into the intake causing the misfire when it reaches the cylinder? Has this been an issue before? 

[GTSBoy]

Turbo coolant leak is almost completely unheard of in the real world.  Nor would it cause a misfire unless it was allowing buckets of water to leak.

You will almost certainly have a BHG or a crack in the head, with BHG being top of the list, when it comes to explaining mysterious coolant loss.  The miss may or may not be associated.

[MJTru]

I agree with above. I first had this same problem when I got a used engine. On mine the head was rotten to the point it would leak coolant into the combustion chamber. Hence the white smoke. BHG or bad head.

[Poketmony33]

The previous owner had it sitting in a shed for a while so that could have rooted the head gasket, maybe due to bad coolant (was very murky when I flushed it). But it was driving perfect till a couple of weeks ago 

[KiwiRS4T]

Try a compression test and/or leakdown test but sounds like head off job.

[Kinkstaah]

Could be worse, I had this issue due to a cracked block.... three times.

But yes, coolant going into the wrong places can cause a misfire. Especially a misfire with white smoke.

[Dose Pipe Sutututu]

1st sentence of 2nd paragraph.

Coolant could be anything from radiator to hear exchange to BHG. 

[Poketmony33]

Could a blown intake gasket also cause coolant to enter the combustion chamber? Or is the coolant return not connected to the intake?

[Dose Pipe Sutututu]

Possible too, coolant does run through the intake 

[GTSBoy]

But on the scale of likelihood.........0.00000001 chance that it's that.

[Poketmony33]

4 hours ago, GTSBoy said:

But on the scale of likelihood.........0.00000001 chance that it's that.

Still a chance though ?‍♂️?

just the symptoms of a bad intake gasket match to what is happening to my car, like missfires, no power/rough acceleration and coolant going down 

[Poketmony33]

The engine has 109,000kms if that makes any difference 

[admS15]

Take it to a decent mechanic and have it checked out. Prepare yourself for bad news and be pleasantly surprised if it's something minor.

[Poketmony33]

The mechanic that I took it to for the fuel flush said it could be a blown head gasket