Hey yall. So I got a 1999 ford ranger 3.0 for about two weeks now my trucks when I start it up idles high for a min then calms down but when im in gear its shakeing and the rpm jump and if I go over 50 it struggles to get up there more soo when I go up a hill.put it on a code reader got codes 301 and 303 what are cyinder 1 akd 3 misfires replace the plugs wires and coils havet drove much but did today ddoing same thing but also today my oil presurse gage is jumping from high to low then it stsyed on low then I shut it off and turn back on it was fine any ideas thanks

 

Here's an article on throttle position sensors I took off of aa1car.com, not saying that this is it though.

DRIVABILITY SYMPTOMS
The classic symptom of a defective or misadjusted TPS is hesitation or stumble during acceleration (in other words, the same symptoms a bad accelerator pump would produce). The fuel mixture leans out because the computer doesn't receive the right signal telling it to add fuel as the throttle opens. The oxygen sensor feedback circuit will eventually provide the necessary information, but not quickly enough to prevent the engine from stumbling.
Throttle position sensors typically experience the most wear in the position just above idle, since this is the throttle's position for most driving. A worn sensor may cause a skip or drop in the reading when the throttle opens, causing a momentary loss of input to the PCM. The result is usually a hesitation or stumble because the PCM fails to provide the necessary fuel enrichment.
If the TPS mounting is loose, it will produce an erratic signal leading the ECM to believe the throttle is opening and closing. The result can be an unstable idle and intermittent hesitation.
If the TPS is shorted, the computer will receive the equivalent of a wide open throttle signal all the time. This will make the fuel mixture run rich and set a fault code that corresponds to a voltage signal that's too high.
If the TPS is open, the computer will think the throttle is closed all the time. The resulting fuel mixture will be too lean and a fault code that corresponds to a voltage signal that's too low will be set.

 

Welcome to FTE.

Good idea to scan & post up the misfire code numbers, post All code Numbers you now have, as they can offer up good trouble shooting clues. After the parts replacement, do you still have the same misfire codes, or do you now have different codes????

Sounds like you may have more than one problem. We're supposed to work the lowest trouble code Number first, & work our way up the list.

Several things can cause a misfire, ignition as you suspected, fuel injectors, compression also, so did you hear the valves or injectors making any untoward noises, or sound different in time with the rough idle or running, or when you listen to them with your stethoscope?????

Did you have arcing & sparking on the old plugs, wires & coilpack, that made you want to change them, or did you just throw some parts at the problem on a hunch???

Because of our "waste spark" ignition system, our engines are kinda persnickety about the plugs & wires we use & Motorcraft parts are of good quality & designed to take the Double work load our ignition system puts on its parts & they, or Autolite who makes fords plugs, are recommended. So what plugs, wires & coilpack did you use, was the spark gap set to spec, the wires properly routed, using All of the factory wire looms & have you had a look under hood after dark, for arcs & sparks, or maybe done a wet down test with a spray bottle of water on the new parts, to see if you have electrical breakdown???? Just because the parts are new, doesn't automatically make em good, I've seen plenty of bad new parts right out of the box, so make those new parts prove themselves.

The IAC is responsible for engine idle speed & is a common problem part, so put it on your suspect list for removal & cleaning with a plastic safe spray, if idle quality is still off after you fix the misfire codes.

More thoughts for pondering, keep us posted on your trouble shoot.