Engine misfire problem
 

Hi , I have a 2000 Ranger 4.0 thats been having some misfire problems lately. It shakes when its at idle, and whenever the engine is cruising at a low rpm (2000 and under usually), but it seems to smooth out when i give it more gas, and let the engine rev up higher. My cel is on and comes back reading two codes (P0153 o2 censor slow response bank 2 sensor 1, and P0303 cylinder 3 misfire). I have changed out the cylinder 3 spark plug and changed all the plug wires. Still misfiring. Changed the ignition coil still nothing.

My question is where do I go next? If i have a vacuum leak would it trigger the P0303 code? Or could that code be triggered by a bad fuel injector? What does the code P0153 mean? Is that code triggered by a vacuum leak, or does it mean I have a bad o2 censor?

thanks

You might have a bad fuel injector or a bad coil pack. I had to replace the spark plugs in cylinder 3 and 2 for the misfire to go away. I have no idea why I had to replace the one in cylinder 2 since cylinder 3 was the one that was misfiring, either way the misfire went away after replacing both. But I also have the dreaded cracked head on cylinder 3 as it keeps cracking the insulation on my spark plug after about a month of using a new spark plug. So Hope you don't have that.

As for the P0153 o2 censor slow response bank 2 sensor 1. The O2 sensor is bad and just needs replaced. It's about a $50 at the autoparts store and real easy to change.

Ok so the code P0153 (o2 censor slow response bank 2 sensor 1) can only be triggered by a bad o2 censor? I just have a stong feeling that I might have a vacuum leak somewhere and I am not sure where to look. If I did have a leak would that trigger the P0153 due to a bad fuel/air mixture or not?

Also where are common areas that the 4.0 tend to leak first?

As the O2 sensors age they become slow hence the code. If you still have the original O2 sensors and 80K or more you should probably change them. I may be mistaken but I think "bank _ too lean" is a common code for vacuum leaks.

thats right

agree with leadfoot, but if you are so sure you have a vacume leak, the two most common are the elbow hose on the right front of engine on the underside. trace your vacume hose from the brake booster and right where it enters the engine, the underside of that elbow goes bad sometimes.
if that isnt the case the second most common vacume leak is from the intake gaskets, piece of advise, if you change the intake gaskets, also change the bolts, the rubber grommets on them go bad as well, and they wont hold the intake down tight enough.

Also found vacuum line from intake to throttle body will be sucked closed. If so replace it. Vacuum leak will not cause misfire code on specific cylinder normally unless that is the first cylinder ecm detects enough misfires to trigger light but other cylinder codes will appear soon if vacuum related. I kept getting misfire codes on different cylinders after approx 6k miles of installing recommended "platinum tipped" (expensive) spark plugs. First time was cylinder 5 next time was 3. Since I accepted the fact that I was going to have to change at least 1 spark plug every 6k miles I requested a standard resistor type (cheapest I could get) spark plugs and added bottle of Barrs head gasket stop leak because I was having to add about 1/2 quart of coolant every month or 2.Since then I have been 24k miles since last misfire code.