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I probably should have mentioned that the car has run great on the same mods and tune for years. I have not modded anything for years - just maintenance.
I was thinking it was the maf but I unplugged it and got error codes. Below is the info I got from the car scanner app
I’m not sure if any of these analytics identify an issue
Last edited by occhevelle; Aug 4, 2025 at 12:48 AM.
get a spray bottle. put water in it. crank engine. spray the exhaust manifolds right by the head for each exhaust port. or if you have headers, spray each tube by the exhaust ports. the water should evaporate very quickly. If it evaporates noticeably slower on one, then theres your problem cylinder. move the coil to another cylinder and test again. If problem moves..its the coil. if not, then dig deeper. May have a broke valve spring or collapsed lifter etc.
Try this or get a ray temp gun so you can Read the temperature all over the engine while it's running if it is legitimately misfiring and The scan is telling you that all the misfire tests are complete then they must be turned off imo
1) Rule out the possibilty of a vacuum leak by spraying around the intake listening for a change in RPM. Maybe recheck the intake manifold bolts to make sure they're properly torqued and rule out any leaks in the induction system.
2) As mentioned earlier take a spray bottle or a temperature gun to determine if you have a cylinder that's not up to snuff. Could mean and faulty plug wire, spark plug or ignition coil.
Are the plugs you replaced the same as the ones in the past? I like the NGK TR6 plugs.
you didnt buy the plugs from amazon did you ? there is alota fake stuff going around. seen it first hand with some ac delco plugs on a tahoe that ran like garbage.. just throwing it out there.
Thank you again for all the responses. I ran it today and it was still running rough and down on power but no backfires. I’m not sure if it’s in my head but it seemed to have a louder tick than usual
I ran a scanner and it did not register any misfires
i I did get the plugs off amazon so that could be the problem - I will buy some new ones
all engine grounds looked good
in addition to plugs I’m going to pull all the plug wires and test with a multimeter to confirm they’re good.
I started to swap the plugs today and found the #2 cylinder plug looks like this (the pic is 2 vs 4) - these plugs have only been on a week or two and have a mile of driving and 30 minutes of idle on them. I'm guessing it's not seating fully and/or I stripped out the plug hole. Could this be the root of all my problems? Also, I'm trying to think of a way of fixing this without pulling the head but I don't think there is any way around that.
Those are auto lite plugs. I did an in line plug tester which showed they were getting spark. And if it wasn’t firing at all I should get a code correct? I’m getting nothing right now
That cylinder is definitely not firing. Check your coil plug. I’ve seen the plugs at the coil get put on a little crooked, and it bend one of the pins over. Same exact outcome…a no firing plug.
You say you're seeing spark with a spark tester and that may be so but you could also have a bad coil there and it's not putting out the correct voltage. Try swapping that cylinder coil with another one and see if the problem follows the coil in question.
Buy a new set of plug wires. If that plug is not seating you will hear it and see the soot trail on the plug and head. Check the coil where the plug wire seats into it, is it rusted or corroded, if so replace it.
This sounds like an intermittent issue that seems to change every time you touch the plugs. In order to remove the plugs you have to move the plug wires, replace them. The most common cause of an intermittent miss is secondary ignition and of those it's usually plugs or wires. The pro's will tell you it's very common to find plug wires not seated properly also.
Yes, I would make sure the plug wires are in good working order and make sure that you have a good connection betweem the electrodes. Not a place to cheap out here either so get a quality set of plug wires.
Swapped the plugs and wires around and ran it for a while and the plug looks clean - I feel pretty good y’all were right about bad plug wires. Waiting on new plugs and wires that get here Monday. Hopefully that’ll do the trick. I’ll post back as soon as I do. Thank you all very much for your time and input.
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