Nissan Repair Questions? Ask a Mechanic for Answers ASAP
I would start by checking the compression in cylinders , we have seen a few 2.5L engines with misfire from power valves in intake manifold screws coming loose and getting into cylinders
wouldnt that occur when the engine is cold and at idle?
they can bend valves or damage your pistons or just close gap on spark plugs
the misfire is random
that seems like a problem directed at a specific cylinder
if you just have a misfire code and no other codes I would start with that the flaps can also block intake ports at times when loose in manifold
only when hot?
you only have a misfire code no other codes?
I would also use a scan tool and monitor fuel trim for a lean condition when hot
thats it.....check the compression?
I have seen some air flow meters not set a code but can cause a lean misfire when going bad
the fuel trim if set high or running to lean can also be your problem
I test drive with my scan tool attached and monitor sensors
seems as though its running rich rather than lean
excess fuel consumption and fuel smell in cabin
are you getting any black smoke out tail pipe?
not that i have noticed
That is strange should smoke when rich and foul spark plugs black in color
just changed the plugs, old ones were somewhat blackened
one more thing to inspect is fuel pressure when misfires could be high or to low and cause a misfire
but it only occurs when the car is hot
sometimes it happens sometimes it doesnt
sometimes it happens and goes away
I test drive with a pressure gage attached and watch pressure it can be worse hot in closed loop from sensors
and if it is?
if pressure problem the pump could be going bad
the fuel pump?
yes if fuel pressure drops when misfiring under a load
if you re oiled your K&N filter this can amage air flow also from oil coating hot wire
i re-oiled the filter in an attempt to fix the problem
it will coat wire on air flow meter if not dry when installed
just one more thing I have seen
i cleaned the MAF with MAF cleaner
also let filter sit for 24 hours after oiling
great I have seen people install them wet and coat air flow
i read something about it possibly being the egr valve
but my understanding is that the qr25de does not have one
they use valve overlap instead
I have seen EGR cause problems on trucks not your car
why would the pcv line pull oil into the intake manifold?
im assuming thats not normal
high vacuum or leaking valve cover could be cracked at pcv passage will suck oil into intake from top of engine are you losing oil also?
also replaced valve cover gasket
how much in 500 miles
about 1qt since last oil change 2000 miles ago
no visible oil leaks around engine
thats not good , could have bad oil rings leaking int combustion chamber fouling plugs
didnt find any oil in the spark plug tubes
it will burn the oil
if no leaks
thats kind of what i was thinking
sounds like it the 2.5L engine I have seen a few burn oil also
if the tube seal was bad that would allow oil into the pcv line, the oil burning would then cause a misfire
if oil in tube will cause a misfire but not a lot of oil
you are not getting a qt. in oil tubes
so where could this leak be?
I would need to make some inspections to know for sure
could be bad rings or valve seal we see more ring problems
piston oil rings
assuming compression test would figure that out
not always but should stat with that
but why would it be a multiple/random misfire unless all rings went bad simultaneously
oil can raise compression and foul plugs then burn off oil at time then refoul them
seems like that would cause a one cylinder misfire if a piston oil ring was leaking
it would cause a misfire in cylinder that has oil fouled spark plugs could be more then one plug also
brand new plugs
as in 2 days old
ok if you new plugs and clean air flow meter , then could be fuel pressure or lean fuel feed back system from bad sensor , this is why you will need to monitor fuel trim also .
you could have more then one problem
Thanks let me know if you have any more questions, ROY!
theres no blue smoke though
will not alway smoke if burning off a little at a time
i have had problems in the past with the car starting due to lack of fuel
but it was very rare
ok I would check with a pressure gage
should keep good pressure
so check cylinder compression, and fuel pressure
yes to start and see if you can get a scan tool that can monitor all sensors if no problems found
at that point its going to the dealer
i guess what it comes down to are what are my options to check at home
that might save you some money to know for sure for installing the wrong parts
at home fuel pressure and compression test
so its probably not a vacuum line?
well i feel this has gone beyond my abilities
im great at replacing parts, but it seems more practical to take it in
I wish you luck and hope it is not very expensive for you , Thanks ROY!
unless the gauges arent too expensive, may need them later anyway
thats true gage can be around $100.00 for both
id just hate to pay 5x as much for a new fuel pump at the dealership when i could do it myself
you can just get it figured out and fix it your self or take some where for less
just pay the diagnostic fee
that is what I would do
save some money that way
alright, well thank you very much you have been extremely helpful
sorry to give you so much trouble i was hoping for an easy answer i might have missed
Thank you also wish I had a easy fix to offer you , good luck ROY!