miss fire/backfire when hot and cold

[ACEAKAI]

I've had this problem for the past 6 or so months after I had put a bottle of injector cleaner in it. when I start it up it goes to high idle then as soon as it starts to come down (after 5 or so seconds) it misfires really hard before going down to idle. when the car is heat soaked (driven like 10 minutes or more) it doesn't let me go above 30-3500 rpm (not like a limp mode but it misfires so much it wont go past) and when at an intersection it stutters and drops rpm into the 200s and sometimes lower. if I'm going around town doing errands and have to start and stop the car it will progressively get worse every start (probably from it getting hot) until I have to give it gas to start. I've changed the coil, distributor cap, distributor rotor, distributor bearing, all vacuum lines and replaced 1 of my two leaking manifold gaskets, the only thing I have changed that "helped" was the bearing but that only made it start a little easier because it was previously solid. I have no check engine lights and no signs of it being a head gasket problem. if anyone has had a similar problem please let me know what i need to replace and or how to test parts that might be the problem because I'm tired of buying parts that don't fix anything.

[gamellott]

I would check the ignition wires. I had a couple of bad ones at one point in time where it misfired because the spark was not getting to the spark plug. If it is a bad wire, you will notice a clicking sound while it's running with the hood open, and there is the possibility that you could get bit by the coil. That's always fun. It's low hanging fruit, but I would also put in some new spark plugs. No need for anything fancy.

 

Also, I experienced a couple of frozen injectors which REALLY sounds like what you're experiencing. I had 2 dead cylinders because of bad injectors and it would still run, just very poorly.

 

You can pull each wire independently while it's running to isolate which cylinder isn't firing, assuming it's consistently the same cylinder. If there is no change in how it runs after pulling the wire, it's associated to that cylinder. If it dies, or sounds worse, its not that cylinder.

 

 

Edited April 24, 2025 by gamellott
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[ACEAKAI]

i wont be able to test today but i could get a video of the cold start, ill try to test tomorrow.

[ACEAKAI]

https://imgur.com/a/abnZihg It cut out the initial start but the initial start is normal