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Major misfire, engine light flashing, P0300 code only
Hummer H3For the Hummer driver who wants the rugged look and off road capabilities of the Hummer, but in a smaller size and with a more fuel economy friendly engine.
Major misfire, engine light flashing, P0300 code only
I am not a mechanic, but I do try to do the minor upkeep myself. I'm sure that's how all mishaps begin. 😉 I was having a little bit of misfire so I decided to change out all the spark plugs and coils. It all went South from here!
Now it won't even go 10 mph before it misfires so bad the engine light flashes and sounds horrible. I have replaced 2 of the new coils finding out they were bad. I again replaced all the spark plugs. I'm going through trying to figure out what the heck happened. This should be a easy fix. I did find a broken hose near the passenger side coming from under the frame by my cat converter.
Help! Broken hose coming from under the vehicle toward engine. What is this?
Major misfire, engine light flashing, P0300 code only
I am not a mechanic, but I do try to do the minor upkeep myself. I'm sure that's how all mishaps begin. 😉 I was having a little bit of misfire so I decided to change out all the spark plugs and coils. It all went South from here!
Now it won't even go 10 mph before it misfires so bad the engine light flashes and sounds horrible. I have replaced 2 of the new coils finding out they were bad. I again replaced all the spark plugs. I'm going through trying to figure out what the heck happened. This should be a easy fix. I did find a broken hose near the passenger side coming from under the frame by my cat converter.
Help! Broken hose coming from under the vehicle toward engine. What is this?
if your new parts where purchased from Ebay or amazon there is a big chance they are counterfeit especially if the price is too good to be true. they do counterfeit sparkplugs and coils to look like OEM and even OEM packaging.
if your new parts where purchased from Ebay or amazon there is a big chance they are counterfeit especially if the price is too good to be true. they do counterfeit sparkplugs and coils to look like OEM and even OEM packaging.
I would not worry about the heater hose insulation, got nothing to do with your ignition issues.
You have an old truck, wire harnesses and insulation become brittle over time and can degrade. Spark plugs still have to be properly torqued to spec, and the coil on plug packs have to be properly seated on top of the plugs to make a solid connection. When you pull them off the ignition coil springs can get crooked (hung up off to the side in the boot) and then not properly snap on the plug. Inspect your work, inspect the coil pack harnesses and make sure you connected them correctly. I would spray CRC Electronics Cleaner on all the connectors while in there.
i believe they have an H2 no coil on pack on those so maybe they need to look at the spark plug wires as well. maybe a terminal end is missing or not fully seated.
i believe they have an H2 no coil on pack on those so maybe they need to look at the spark plug wires as well. maybe a terminal end is missing or not fully seated.
2006 H3 Hummer Ignition Coil On Plug Pack.
Last edited by Doc Olds; Nov 15, 2023 at 09:36 AM.
Major misfire, engine light flashing, P0300 code only
Btw, P0300 stands for “Random or Multiple Cylinder Misfire Detected”! Clean the valves! 
