Misfires after plug change
#1
Misfires after plug change
So I know this sounds like an easy one but I'm stumped. Changed the plugs over the weekend and finally got around to a test drive today. Getting misfires on cyl 4&6. Both on the driver's side of course, which is the hard side. However all coils are seated and plugged in, nothing was missed as far as I can tell. Anyone have any suggestions?
#2
So I know this sounds like an easy one but I'm stumped. Changed the plugs over the weekend and finally got around to a test drive today. Getting misfires on cyl 4&6. Both on the driver's side of course, which is the hard side. However all coils are seated and plugged in, nothing was missed as far as I can tell. Anyone have any suggestions?
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Hi Doc Oc,
Sorry to join your thread late. A few possible causes I can think of are:
1. Did you use the correct OEM plugs? (I don't see that you have told us the year, model and engine of your car)
2. Did you apply anti-seize compound to the plug threads? Today's plugs do not need anti-seize and the compound can add resistance that interferes with spark (and leads to over-torquing the plugs).
3. Was there oil in the spark plug tubes? If so, oil baked onto the spark plug port threads can add resistance that interferes with spark.
4. Were the plugs properly torqued? Loose plugs will cause low compression and misfires.
5. Are the coil wires in good condition? The insulation on the coil wires can harden and crack, leading to shorts or broken wires.
6. Is it possible a crankcase breather hose or vacuum hose was damaged during the plug replacement procedure? Leaks in hoses can cause the bank to which they connect to run lean, resulting in misfires. Have you checked your fuel trims?
Beyond that, Carbuff2's idea of swapping coils with non-misfiring cylinders would be a good next step to rule out coil failure.
Cheers,
Don
Sorry to join your thread late. A few possible causes I can think of are:
1. Did you use the correct OEM plugs? (I don't see that you have told us the year, model and engine of your car)
2. Did you apply anti-seize compound to the plug threads? Today's plugs do not need anti-seize and the compound can add resistance that interferes with spark (and leads to over-torquing the plugs).
3. Was there oil in the spark plug tubes? If so, oil baked onto the spark plug port threads can add resistance that interferes with spark.
4. Were the plugs properly torqued? Loose plugs will cause low compression and misfires.
5. Are the coil wires in good condition? The insulation on the coil wires can harden and crack, leading to shorts or broken wires.
6. Is it possible a crankcase breather hose or vacuum hose was damaged during the plug replacement procedure? Leaks in hoses can cause the bank to which they connect to run lean, resulting in misfires. Have you checked your fuel trims?
Beyond that, Carbuff2's idea of swapping coils with non-misfiring cylinders would be a good next step to rule out coil failure.
Cheers,
Don
Last edited by Don B; 08-09-2024 at 08:43 AM.
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#12
Hi Doc Oc,
Sorry to join your thread late. A few possible causes I can think of are:
1. Did you use the correct OEM plugs? (I don't see that you have told us the year, model and engine of your car)
2. Did you apply anti-seize compound to the plug threads? Today's plugs do not need anti-seize and the compound can add resistance that interferes with spark (and leads to over-torquing the plugs).
3. Was there oil in the spark plug tubes? If so, oil baked onto the spark plug port threads can add resistance that interferes with spark.
4. Were the plugs properly torqued? Loose plugs will cause low compression and misfires.
5. Are the coil wires in good condition? The insulation on the coil wires can harden and crack, leading to shorts or broken wires.
6. Is it possible a crankcase breather hose or vacuum hose was damaged during the plug replacement procedure? Leaks in hoses can cause the bank to which they connect to run lean, resulting in misfires. Have you checked your fuel trims?
Beyond that, Carbuff2's idea of swapping coils with non-misfiring cylinders would be a good next step to rule out coil failure.
Cheers,
Don
Sorry to join your thread late. A few possible causes I can think of are:
1. Did you use the correct OEM plugs? (I don't see that you have told us the year, model and engine of your car)
2. Did you apply anti-seize compound to the plug threads? Today's plugs do not need anti-seize and the compound can add resistance that interferes with spark (and leads to over-torquing the plugs).
3. Was there oil in the spark plug tubes? If so, oil baked onto the spark plug port threads can add resistance that interferes with spark.
4. Were the plugs properly torqued? Loose plugs will cause low compression and misfires.
5. Are the coil wires in good condition? The insulation on the coil wires can harden and crack, leading to shorts or broken wires.
6. Is it possible a crankcase breather hose or vacuum hose was damaged during the plug replacement procedure? Leaks in hoses can cause the bank to which they connect to run lean, resulting in misfires. Have you checked your fuel trims?
Beyond that, Carbuff2's idea of swapping coils with non-misfiring cylinders would be a good next step to rule out coil failure.
Cheers,
Don
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#16
Very little difference over the model years, same OEM spark plugs for all.
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Doc Oc (08-09-2024)
#17
So turns out, as often seems to happen to me in car life, the problem wasn't even spark plug related! Just so happens that while I have been working on the car over the last month, the solenoid for my snow WMI system had failed. No check valve so every time I started the car it was sucking in a ton of meth, causing misfires. Finally got a boost sensor code which I have seen before when the wmi sprays at too low of a boost level and floods things. Removed the meth and car runs like a top. How weird! But thanks so much for everyone's input!! Heading to the mountains and Tail of the dragon tomorrow so I was in a huff! So glad to have it running
Last edited by Doc Oc; 08-09-2024 at 06:29 PM.
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Actually, he never even told us it was an F-Type (he still hasn't), so all we can do is guess that he is in the correct forum. But at least we now know it has the Snow Performance water-methanol injection system... Might have been helpful to know in Post #1...
Last edited by Don B; 08-09-2024 at 10:55 PM.
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#20
It's very helpful to visit your User Control Panel and edit your signature to include the year, model and engine of your F-Type so this information appears in all of your posts so other members can give you the most accurate responses.
Thanks for reporting back with the cause of your misfires. This is how we all learn!
Cheers,
Don
Last edited by Don B; 08-09-2024 at 10:54 PM.
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