WaltL

Wife's car: I did a stock JDM motor swap on her '03 GS300 about 3 years ago and used my old wiring harness and coils (new plugs). Car has run flawlessly since and it's a commuter that gets about 50 miles/day put on it.

About 2 months ago the car starts hesitating and throws a dtc for mult. random misfire and #4 misfire. So I put some Techron cleaner and new gas and after awhile problem goes away. Then, right before a 1000 mi round trip, it started hesitating again (but the cel never came on) and I did the same thing- cleaner and gas. Problem went away for the whole trip and then returned when we got back with a dtc for only #4 misfire. I reset and drove a bit and it's still hesitating, but no cel yet.

I tend to think coil rather than injector, but I didn't realize until now that there are only 3 coil packs. So wouldn't I expect to see misfires on 2 cylinders if the coil is bad? Also, the car itself has ~ 200K and I have never changed the plug wires, but I would think the problem would be less sporadic if it were a wire.

Anyone had/seen a similar issue? I guess the coil in question would be the center one and supplies power to #'s 3 & 4?

Walt

Mr Jokster

iTrader: (8)

First thing to rule out the coil, swap it with the one in the front and play the waiting game. When it throws the code again, see if the code reads on a different cylinder. If it does, then you know its the coil. While you're in there, remove the plug from cylinder 4 take a look in the shaft and see if there is any oil or some type of build up. Could be a intermittent oil leak creating some bad connection. Just a thought, but yea, swap the coils and see if the code follows.