Thread: Misfires, raw fuel smell, codes p0128 p0300

Looking for some ideas on this one. Had to have the regal towed back home this morning. With no warning, started running rough and was way down on power. Getting HEAVY fuel smell out exhaust, and these codes:

p0128 coolant thermostat
p0300 Random/multiple misfire
p0420 Catalyst below efficiency, bank 1

I believe the 0420 has been there since I installed the ZZP DP several years ago. The raw fuel smell is very strong, like straight fuel out the tailpipe. Any ideas where to check first? I'd appreciate any help.

If you smell raw fuel, better check all your fuel line fittings for leaks, especially where the fuel lines connect to the fuel rail.

your catalytic converter could be plugged causing the computer to dump fuel in it to try and clean it out. on a separate issue, your thermostat could be stuck open causing the engine to run rich. I would put a new thermostat in and see if that fixes one of your problems.

Thanks guys. I will start with the t-stat and go from there. I'll have to dig out my receipts and see when things were last replaced. There def is not a fuel leak though- it's unburnt fuel dumping out the exhaust. It will be a couple days, but I will post back with findings.