Hello Scotty!
I bought a 2001 Mazda tribute 2.0 awd with 315 k kilometers for 2000 euro (it's cheap for what they go for around here) and it has a misfire on the number 1 cylinder and the long term fuel trim is adding 24%. I'm thinking about replacing the spark plugs and cleaning the air flow sensor and throttle body, maybe that will sort it out. The ignition coil is new. My question is, after I do all that and it's still running rich should I check the injectors? The car runs just fine now, it accelerates well but when it's idling it's vibrating and it seems like only three pistons are firing although it doesn't have variations in rpm (checked all the parameters with the creader from launch that you recommended, which works great, thx for the tip).
Love your show, keep sending that info for all those who devour it!
You say the LTFT is adding 24%.
The engine isn't running rich. It's running lean.
So why is that?
Maybe hook your scanner back up and select Live Data.
Watch the fuel trim at idle. Then rev the engine up to around 2500 rpms, hold it there for a little bit, and see if the fuel trim goes down.
If it does, look for a vacuum leak.
If it doesn't, and since you have a persistent misfire on cylinder #1, maybe attach a fuel gauge to your fuel rail, switch the key to ON to build fuel pressure. Turn the key to OFF. Disconnect the wire connector from the #1 injector and apply 12 Volts to one terminal on the injector and Ground to the other terminal on the injector.
The fuel pressure on the gauge will go down if the injector is opening.
This isn't a conclusive test by any means. It could be that the injector isn't opening all the way. Could be a problem with the wiring to that injector.
But if the pressure doesn't go down at all, then the injector isn't working at all
Swap the ignition coil on cylinder 1 with 4. If the misfire moves, then change the ignition coil. Replacing the spark plugs and clean the MAF sensor and throttle body is a good practice.
