Dustinalberta

Okay so I joined this forum because of this problem I have looked everywhere and have yet to find a solution. Here's my issue: it just started getting cold up here in Alberta and every morning now I'll go out to start my truck and it starts fine but has a high idle of about 3000 then drops to 500 and tries to stall I need to sit pushing on the gas for about 5 minutes until things warm up. Only code it throws is a flashing CEL P0300 but it has also thrown p0420 and p0430. I have cleaned the map aswell as the throttlebody. I'm leaning towards a gasket seal but I'm not sure. Also when this is happening sometimes there's black liquid that comes out of the exhaust. This all only happens on cold start morning when it sits ALL night and the truck runs great all day afterwords

cleveland63b

do you have a scanner? check the fuel trims? symptoms sound like a vacuum leak possibly intake gaskets, flashing p0300 means you have a dead miss, scanner misfire data would show which/how many are missing. Details mean everything in diagnostics

Dustinalberta

What am I looking for when looking at the fuel trims?

cleveland63b

idling or at a set cruise they should be between 10% and -10% at all times. If its above 10 at idle you probably have a vacuum leak. Quickest way to narrow down where is watch the short term (stft) and put alternate fuel around where you suspect a leak (for example spraying brake cleaner around the intake gasket area) and the fuel trims should drop while adding.