I have a 2wd 2000 4Runner Limited with the 3.4L V6 and 172k miles.

A month ago we noticed the check engine light began flashing occasionally, usually 4 flashes and then it would disappear. One evening the engine all of a sudden began running very rough, the check engine light flashed several times, and then stayed on. We took it to a mechanic and were told that one of the spark plug wires had a cut in it and was shorting out. We decided to change all the wires and plugs to resolve the issue. We were also preparing for a 3500 mile trip so we wanted things in working order. The plugs that were put in were Champion 3318's.

The 4Runner ran well and we made the outbound portion of our roadtrip. Heading back a week later, the check engine light began flashing occasionally again, usually 4 times, occasionally 8 times, and once 16 times. We had been told that the 4 flashes meant a misfire and I assumed the same problem had not been fixed. With around 1,000 miles left on our trip, the check engine light came on constant, with the flashing continuing on occasion, and the engine developed a noticeable vibration. This vibration was not nearly as severe as what happened the first time. We stopped at a Midas, the only thing open where we were. After looking it over they said we had the wrong spark plugs, cold tip vs hot tip. They put in Denso (1394) K16TR11 plugs. This seemed to help a little bit with the vibration, but it was still there and after a couple hundred miles the check engine light came back on solid, with the same flashing.

I will probably take it back to the same mechanic that replaced the wires and plugs the first time, but I'd like to get some input on what needs to be looked at before I do. Thanks for any suggestions.

 

What needs to be looked at depends on the code the CEL is giving. Some part stores have a code reader you can borrow to read the code.

Post up the code and you'll get more specific responses.

All ground wires firmly attached?

 

I don't have access to a parts store with a code reader around here, but the mechanic should be able to check it out if I take it back to him. I will look again at wires including ground wires.