Spark plug replacement resulting in misfiring - 451

…were the old plugs dirty/oily in the thread area???
…go back when it was normal…
…we are talking about a 451 model???

jetfuel…we’ll wait

1 of the old plugs appeared to have some build up, rusty color. The other plugs looked fine, they are all OEM Denso type, old and new ones. This is a 451 model. When I disconnected the battery negative terminal, everything seemed fine for a few minutes, and then went to the misfire condition again. Codes showing misfire on 2 cylinders. Spark plug gap checked, no adjustments required.

Try swapping the plugs between cylinders. If the misfire changes to a different cylinder, try a new plug. It’s rare, but not unheard of or have bad one from the factory.

If it stays on the same cylinder, try swapping the coil from another cylinder.

…put the old plugs back on….
….make sure there’s a spring connector at the end of the plug boot….I got one come off and ended resting on top of the piston….not an easy rescue…

jetfuel….see what happens

Mini M, You said one plug had a dark color that looked like rust, was that on the inside surface of the plug or the outside? If inside then you are looking at coolant getting in the combustion chamber.

First place I’d check….Make sure your coil packs are on tight

If you have done a few smart spark plug changes then it’s either something was moved out of place, something fell in the spark plug hole or a bad plug…..But I’m guessing

Any chance it could be related to the crank positioning sensor malfunctioning? I'm planning to check the compression, and will try some of the suggestions above is nothing is obvious in the various checks. In addition, what it the normal temperature people are experiencing in the catalytic converter?

jetfuel said:

…put the old plugs back on….
….make sure there’s a spring connector at the end of the plug boot….I got one come off and ended resting on top of the piston….not an easy rescue…

jetfuel….see what happens

Click to expand...

Springs are definitely in place, as I removed the bottom boots and checked the internals for cleanliness, corrosion, and broken spring, no issues discovered. I'll try the plugs.

…if it was running fine before the plugs why make your life harder???
…if crank sensor is bad it will not even fire…magnetic pick-ups (monopoles) don’t kind of intermittently fail …they go open circuit thus hard fail…seen them fail after a heat soak … you can measure resistance cold and then again after it develops the failed symptom…
…lifting the body only by lifting points makes getting to the plugs a piece of pie…

jetfuel…LUK

jetfuel said:

…if it was running fine before the plugs why make your life harder???
…if crank sensor is bad it will not even fire…magnetic pick-ups (monopoles) don’t kind of intermittently fail …they go open circuit thus hard fail…seen them fail after a heat soak … you can measure resistance cold and then again after it develops the failed symptom…
…lifting the body only by lifting points makes getting to the plugs a piece of pie…

jetfuel…LUK

Click to expand...

"…lifting the body only by lifting points makes getting to the plugs a piece of pie", I like it, never thought of this practice.

What plugs did you use?

Where did you get them?

Did you use antiseize?

When installed, where you careful about cross threading?

A piece of tubing, stuck on the end of the plug, makes initial install easy.

Spark plugs replaced with original used ones, no changes to misfiring. The OBD indicates that all cylinders are experiencing this misfiring, there doesn't appear to be any oil emitted from the exhaust, and by all accounts of a compression test, cylinder 1 is a bit low due to valve leakage as added some oil to each cylinder to confirm if the piston rings were the cause. As I just purchased this car from a previous owner, I wonder if the fuel might be an issue, or perhaps the O2 sensors, if they were running lower octane fuel during its life. Car has 32K kms.

…believe me…or not…lower octane will not create a misfire… ….bad/contaminated fuel will…

jetfuel…??

Almost thought it was solved, put some fresh fuel in the tank along with Royal Purple injector cleaner. Had a code P016, crankshaft position correlation bank 1 sensor A. I replaced the crankshaft position sensor, and the engine seemed to be stable with no more trouble codes. Connected the OBD reader, went live, and drove for 20 minutes around town. At the end, the engine light came on, felt like a cylinder was misfiring again, and limped the car back to the driveway. OBD indicates all cylinders are misfiring [P0300/301/302/303] and the P0012 and P0016 [related to camshaft and crankshaft position] I'm stumped, again.

I also checked the injectors, all seemed very clean and not leaking fuel at the nozzles. I didn't confirm the spray patterns, so restricting flow is a potential, hence the injector cleaner additive.

BTW, what is the catalytic temp suppose to be, I was watching it during my ride at various rpms, and noticed it can reach the mid 700 Celcius range.