Slight misfire when cold, fine when warmed up
#1
Slight misfire when cold, fine when warmed up
Hi all, I have a 08 g35 and I'm getting a slight misfire when the car is cold. After the car fully warms up the misfire disappears.
When cold, the car starts fine, idles fine, no misfire (from what I can tell) at idle. But as soon as I start driving it, with throttle at about 10% or more I will hear a misfire. I have changed spark plugs (old plugs looked normal) and checked the coils but misfire is still there.
There are no codes when I scan for them so I'm not sure where to go from here. Maybe injectors?
I looked around and found this video:
My car is basically doing the same thing.
Thanks
When cold, the car starts fine, idles fine, no misfire (from what I can tell) at idle. But as soon as I start driving it, with throttle at about 10% or more I will hear a misfire. I have changed spark plugs (old plugs looked normal) and checked the coils but misfire is still there.
There are no codes when I scan for them so I'm not sure where to go from here. Maybe injectors?
I looked around and found this video:
My car is basically doing the same thing.
Thanks
#2
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Are you SURE it's a misfire? You feel a sudden loss of about 20% power? I've seen MANY "cold engine misfires" that were actually very small exhaust leaks that would be more prevalent when cold and under moderate throttle before the pipes have expanded due to heat.
Did you use Denso FXE24HR11 spark plugs?
I would start by following the steps in the FSM which usually go something like.
-Remove fuel pump fuse
-Crank/run motor and run until it stalls
-Crank again 2-3 seconds to remove all fuel pressure from the line.
-Remove coils and all spark plugs
-Check resistance with a digital multimeter between the 3 pins of the coil (pin1-pin2, pin1-pin3, pin2-pin3) verify you don't have one coil pack with an odd reading.
-Physically inspect each coil pack for blistering of the resin encapsulation (shiny black) part on top or burning/scorching/discoloration/tears of the spark plug well boot, or corrosion on the harness pins / spark plug contact spring
-Attach 1 coil pack at a time with a spark plug installed, hold WITH A LEATHER GLOVED HAND the spark plug ground strap (hook part at the end) 1/2" from grounded engine metal or chassis metal (intake manifold works perfect) while a second person cranks the motor and you visually watch spark.
-Rinse/repeat for each coil pack
If you hold the spark plug with the ground strap directly touching the intake manifold it will almost always show spark so you need that 1/2" gap, the system operates at something around 15-20k vdc so it will bridge the gap if everything is working properly. Try to be accurate with that distance, too great a distance causes amp spiking which can damage the coil over time.
Did you use Denso FXE24HR11 spark plugs?
I would start by following the steps in the FSM which usually go something like.
-Remove fuel pump fuse
-Crank/run motor and run until it stalls
-Crank again 2-3 seconds to remove all fuel pressure from the line.
-Remove coils and all spark plugs
-Check resistance with a digital multimeter between the 3 pins of the coil (pin1-pin2, pin1-pin3, pin2-pin3) verify you don't have one coil pack with an odd reading.
-Physically inspect each coil pack for blistering of the resin encapsulation (shiny black) part on top or burning/scorching/discoloration/tears of the spark plug well boot, or corrosion on the harness pins / spark plug contact spring
-Attach 1 coil pack at a time with a spark plug installed, hold WITH A LEATHER GLOVED HAND the spark plug ground strap (hook part at the end) 1/2" from grounded engine metal or chassis metal (intake manifold works perfect) while a second person cranks the motor and you visually watch spark.
-Rinse/repeat for each coil pack
If you hold the spark plug with the ground strap directly touching the intake manifold it will almost always show spark so you need that 1/2" gap, the system operates at something around 15-20k vdc so it will bridge the gap if everything is working properly. Try to be accurate with that distance, too great a distance causes amp spiking which can damage the coil over time.
Last edited by cleric670; 12-24-2017 at 02:26 AM. Reason: clarification
#3
That having said, I haven't thought about it being an exhaust leak. I never really took notice of power loss since I wasn't accelerating hard enough to notice it, but I'll try that soon.
I replaced with the factory plugs, which were the densos that you mentioned.
I've already checked resistance of the coil packs and all of them were very close to each other.
I replaced with the factory plugs, which were the densos that you mentioned.
I've already checked resistance of the coil packs and all of them were very close to each other.
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#8
Just tried that. Had it in manual mode in 2nd so rpms wouldn't go crazy high and had it WOT from 2k to 3kish rpms. The "misfire" got louder when I went WOT, but I didn't really notice any loss of power or inconsistency with power delivery.
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