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p0300 is random misfire and p1516 is throttle actuator performance of voltage issue. you may have a faulty throttle actuator which is causing the random misfire. the b0299 is a fault related to a body component which may or may not be related to the primary "p" codes.
Multiple Cylinder Misfire Detected Possible Causes:
Base engine mechanical fault that affects one or more cylinders.EGR valve is stuck open or PCV system has a vacuum leak EVAP system problem or the EVAP canister is fuel saturated Fuel metering fault that affects more than one cylinder Fuel pressure too low or too high, fuel supply contaminated IC control circuit is shorted to ground (an intermittent fault)Ignition system fault (a coil) that affects more than one cylinder MAF sensor contamination (it can cause a very lean condition)TSB 03-06-04-030 contains a repair procedure for this code
po300 is random miss fire doubtful two O2 sensors bad at one time most likely coolant temp sensor is bad causing engine to run rich this will cause O2 sensors to throw a code(thats what they are there for..exhaust gas temp. and raw fuel) running rich will also fowl spark plugs(=miss fire) P1128 ??
Air leak in the intake manifold, or in the EGR or PCV systemBase engine problem affecting two or more cylindersCMP or CKP sensor signals erratic or out of phaseEGR valve stuck open, or EVAP purge system has failedFuel delivery component fault that affects more than 1 cylinder (i.e., contaminated, dirty or sticking fuel injectors)Ignition system problem affecting two or more cylindersVehicle driven while quite low or until it ran out of fuel.Here's the other code P0011.
Which engine does your Expedition have? The P0171 could be a PCV system issue, possibly an EGR issue, intake manifold gasket issue, etc. The P0300 could be a vacuum leak such as those mentioned above as well, but the P0302 and P0171 would probably point more to Bank 1. Based on these three diagnostic codes it does seem likely that one issue will probably fix all three diagnostic codes. I think you're correct in looking for vacuum leaks, but depending on the engine in your Expedition, intake manifold gaskets and the EGR system are a couple of candidates that you maybe haven't considered yet.
You have a random engine misfire. P0300. That is the root cause. Basically this P0300 code means that the car's computer has detected that not all of the engine's cylinders are firing properly. This would also cause hard shifts due to low engine power. Read on please.
A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why. Symptoms: •the engine may be harder to start •the engine may stumble / stumble, and/or hesitate •other symptoms may also be present Causes: •Faulty spark plugs or wires •Faulty coil (pack) •Faulty oxygen sensor(s) •Faulty fuel injector(s) •Burned exhaust valve •Faulty catalytic converter(s) •Stuck/blocked/leaking EGR valve / passages •Faulty camshaft position sensor •Defective computer
Engine is running rich--may be the cause of the misfire code as well. Couple things to try. First, clean the MAF sensor by spraying with electrical parts cleaner. Also, try adding some injector cleaner to the tank.
Had the same problem on my brothers Rav4. We changed the Plug wires and the problem is corrected. He had changed the plugs a couple of months ago. We had the code read at Advance Auto, it came up P0300 Random misfire. His old wires looked fine also.