What else should I look at? (1 Viewer)

[moab_b2]

So we have a 1996 Lexus LX450 with 217k miles. Out of the blue after a 60 mile freeway trip we started getting some bad misses. Parked it while at a soccer game and when we left, the same miss the whole way home with the CEL flashing at me.

Got home and the code was P0306. So the only cylinder code was 6. I ran it while reading the code and it smelled of very strong raw gas smell. No steam or smell of burning anti-freeze.

So I checked the anti-freeze level, and its still full with no oil in it. Checked the oil cap no foaming oil soup either. I pulled the ECU at the passenger kick panel and checked for shorting wires, and its all good. Opened up the wires at the EGR and all seemed good (although it was hard to get very close to it due to it being so far from the front of the vehicle.) Pulled the spark plugs and #6 was a little oily but not too bad BUT was wet with gas. The rest were normal. I will check gap on them all after cleaning them. Checked the spark plug wires with an meter and they all were between 2000-800 ohms. Did not see any cracks in them. The wires and plugs are a year and a half old with maybe 12k miles.

I pulled the valve cover off and plan on replacing the gaskets to stop some of the leaks. I also will change out the distributor cap and rotor (look worn). I also plan on removing the rest of the heat tape on the wires past the EGR to make sure I am not shorting out lower than at the closest part.

Is there anything else I am missing? I have read hours of posts, but I bet I have forgotten more than I care to admit.

 

[drowssap]

Cap and or rotor?

 

[moab_b2]

Ya I have them on the way to me.

 

[drowssap]

Have you checked the old parts? Any arcing?

 

[moab_b2]

In the cap? If so then no evidence of it, just the contacts look pretty worn. Same worn viewed on the rotor. The plug doesnt look like its arcing anywhere but to the ground strap.

 

[BlueCruiser84]

Stuck injector? Cracked/bad plug?

I don't know if you can get a screwdriver down to the injector. If so, hold the tip on the injector and push the handle into your ear. See if you can hear it clicking.

 

[newtomelx]

Check your wiring right where it passes the EGR valve, that was my issue when I had a P0306

 

[ZackR]

I had misfires caused the wiring near the EGR. It wasn't obvious until I removed all of the insulating material and could see the wires themselves. Luckily in my case I only had to repair three wires and it was good to go.

 

[blkprj80]

There is +12V on one side of your injector. That's the black wire with a red stripe.
The other wire is "pulled to ground" by the ECU to fire the injector. This a pulse, to provide the precise amount of fuel.

If, somewhere in your harness, that other wire is shorted to ground, your injector will be stuck full-on. This short can happen by the EGR tube, and it can also happen under the dash near the ECU on a sharp corner.

Did it seem like it was using a ton of fuel during the drive?


I had a P306 one time after I washed my engine. I am pretty sure it was the distributor cap got wet somehow. It went away and I didn't feel like chasing it. I'd be interested to see if your new cap fixes things.

 

[moab_b2]

I was not paying attention to the fuel usage, as I was just hoping that it didn't die a hour away from home. I have checked the ECU harness behind the glove box and also right at the EGR. I will expose even more of the harness in the engine bay and try to get a closer look.

 

[Ocho77]

May be too little too late since it sounds like you have it torn apart already, but I had the same issue...happened out of nowhere. Shut it off, pulled all the fuel relays from the DS kick-panel and disconnected the battery. Waited 30 minutes, put the relays in and connected the battery. For some reason it solved the problem.

 

[moab_b2]

Ocho77, the top of the motor is already torn apart... Oh well, I will do all the PM that I have listen and still do what you did just in case. Cant hurt, right?

 

[LandCruisinMy93]

I suspect either a bad injector or a wiring issue. You should get a spray bottle with some lightly salted water spray around the plug wires on the valve cover to check for arcing.

 

[moab_b2]

So while inspecting the wire harness, I did not find any wires shorted out. I then inspected the injector line to the #6 injector and noticed that the yellow/blue wire had shorted against the vertical metal piece. It rubbed through the shield and insulation and it had noticeable scorching on it. Fixed that and will put everything back together tomorrow. I am glad I found the cause of the misfire. It was driving me crazy not knowing exactly the problem was.

 

[blkprj80]

So while inspecting the wire harness, I did not find any wires shorted out. I then inspected the injector line to the #6 injector and noticed that the yellow/blue wire had shorted against the vertical metal piece. It rubbed through the shield and insulation and it had noticeable scorching on it. Fixed that and will put everything back together tomorrow. I am glad I found the cause of the misfire. It was driving me crazy not knowing exactly the problem was.

Got a pic of the area it was shorted, and the metal piece it was shorted on?

Glad you found it!

 

[moab_b2]

No I fixed it before I even thought of pics. The metal piece it shorted on was the vertical metal that looks like it's there to support the injector wire. Mine wasn't supported just resting on it. This is injector#6.

 

[moab_b2]

Oh ya it was the yellow/blue wire that shorted.

 

[moab_b2]

So the wires were found/fixed, valve cover gaskets replaced, spark plugs cleaned and regapped, EGR system cleaned up, ditributor cap and rotor replaced. After it was all buttoned up, it fired right up and idled smooth. Drove about 20 miles and the engine seems better than anytime we had it (over 8 years). Great help on this forum. Thanks guys.