2000 Montana with P0300 code

[gt4ms]

My service engine light came on.Ran rough for a bit and wouldnt idle. Bought a code scanner and came up with P0300. very hard to start up now,hot or cold, idle lopes about 500 rpm up and down.highway,city driving it is fine.Notice a bit of a miss when stopped at lights.Also smell of fuel when shut down.Vehicle has 135000 kms on it. Any ideas? thanks in advance

[rjer3]

When was the last time the spark plugs were changed? the timing could be off which in result of the timing belt needs replaced. but it is diffently ignition or timing.

P0300: Random Misfire Detected

[GTP Dad]

In addition to the plugs change the spark plug wires. They usually go bad and will cause random misfires. Also bad wires can destroy coils if they aren't changed.

[wafrederick]

Change the plugs first,see what it does and stay away from Bosch plugs sticking with AC Delcos.Could be headgaskets too,working on one with this happening after changing the plugs with the #1 cylinder and the rear headgasket was junk.The #1 chamber was clean and not carboned up showing an indication of of a bad headgasket.It is not timing,has a timing chain,not a timing belt which will last a long time and the computer does the timing.

[hufhouse]

Have you ever changed the fuel filter?

I think I would eliminate all "maintenance" items, like the plugs, wires, fuel filter, air filter, etc. Get rid of any "weak links."

[gt4ms]

they changed the fuel pressure valve.seemed ok, now it just hunts around a bit when you start it up.