2000 exp sport OHV mis-firing.

[nitrowizard88]

Last week my exp. sport gained a mis-fire. I took it to a local auto repair and he diagnosed the problem to a back O2 sensor by the catalytic converter. He said it wasn;t getting any voltage. So I replaced the sensor and it did not fix the problem. . Thank god my local parts dealer let me exchange for a different one. I have three sensor location and I changed them all one by one. None of the sensors fixed the problem. I also used carburator cleaner to find a vacuum leak. No leaks.
All the plug wires are connected. So is there something else I can try or does anyone have any ideas? Could the actual wire to the the sensor from the computer be bad or burnt ect.???

Thanks in advance

[shorod]

A bad O2 sensor will not cause a misfire, but a misfire might cause a bad reading from an O2 sensor. If you've accurately repeated what the shop told you, you should consider finding a new shop.

Also, the O2 sensor portion generates a voltage. If the comment regarding the sensor not getting any voltage to it, that would need to be for the heater portion. The diagnostics for this are pretty good. If you have an open wire for the sensor or for the heater circuit there should be a diagnostic code for it.

A professional grade scan tool should be able to monitor the misfire counts on individual cylinders to help determine which cylinder or cylinders is/are misfiring, even if the misfire is not bad enough to trigger a diagnostic code. If you're certain the problem is a misfire and the shop does not have a scan tool capable of confirming this, again you should find another shop. In the long run, having the proper tools to diagnose modern cars will save money.

Start by checking for diagnostic codes. Many of the chain auto parts stores will offer this service at no cost. If there are no diagnostic codes, then you either need to assess the age and condition of the spark plugs and spark plug wires and decide if you're due to change them anyway. Keep in mind that the plug wires can look pretty good but still have problems.

If the misfire is pretty constant you could try disconnecting one wire at a time (for a short time) to determine which cylinder is not contributing. When you find one plug wire that when disconnected does not impact the way the engine runs, or at least not as much as the rest, that is the cylinder that is not reliably contributing.

-Rod

[rait63]

Agree with Rod's thoughts. Any chance you've replaced the spark plugs recently? I did about 6 months ago with a set of Bosch plugs. The engine began misfiring after about 20 miles. Don't know whether it was a defective plug or not, but I switched to a new set of Motorcraft on the recommendation of the mechanic and haven't had a recurrence in 15,000 miles.

Steve
2004 SportTrac XLT

[nitrowizard88]

I am here replying to ROD to say a BIG FAT THANK YOU!!!!!!

Turns out I had a couple plug wires that were well i would say..ATE UP! changing plug wires and plugs fixed the issue. My Explorer works just fine noe. Thank you very much for your advice. I love this site! I am going to go ahead and change fuek filter also to better my fuel mileage also. Thanks again

Mark

[shorod]

Thank you for the follow up and I'm glad the forum could be of help to you!

-Rod