Toyota 4-Runner misfiring


Old 07-13-05, 06:38 PM
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Angry Toyota 4-Runner misfiring

I have a 99 Toyota 4-Runner 4WD, 3.4L V-6 with 103,000 miles. I first noticed a miss that got worse over about a week then the Check Engine light came on. The code for the OBD II scan showed "PO0300 Random/Multi cylinder misfire" and "PO303 Cylinder 3 misfire". I also got "P0302 and PO306 for cylinders 2 and 6 misfire" but the 2 and 6 only read once. I keep clearing the codes and the ones that keep coming back are "P0300 and P0303" I have changed the spark plugs and plug wires, I have changed the fuel filter. I have checked the coil paks and the primary and secondary resistance are with tolerance as found in the Haynes Manual. When the engine is cold it seems to run better. The missing is most noticable when accelerating from a stop and when running at a steady speed on a uphill grade. When I give it more gas the miss seems to go away and it accelerate pretty good then. Any help would be appreciated. Thanks, Mike
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Old 07-13-05, 07:48 PM
Join Date: Nov 2001
Location: North Texas
Posts: 2,345
Try this

I have a Toyota Corolla had that code of multi cyl missfire.I bought a can of Heet and put it in the fuel light went off after a few engine cycles.Seems I had a bit of water in tank.Total cost about a buck.
I also noticed that when I start car for first time and turn on A/C it idles rough this could have also caused it.I now wait to turn on A/C till engine warms up about 1-2 min.
Old 07-13-05, 08:44 PM
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Your engine (5UZFE) has individual coil packs over each spark plug, as you probably know...It's very common for those to have intermediate failure before they finally poop out on ya. But since there is more than one cylinder that is misfiring, I would suspect the igniter. I would have that checked.
Old 07-14-05, 06:35 PM
Join Date: Jun 2002
Location: Long Island, NY
Posts: 1,531
Switch coil pack with a different cly and see if the miss follows
Old 07-14-05, 06:45 PM
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Originally Posted by toyotaman11769
Switch coil pack with a different cly and see if the miss follows
Yea, I was just thinking of doing that since I just got codes for multi cylinder miss, and cyl's 3 and 6 miss. I believe that 3 and 6 are companion cyl's and that those two could mean the same coil pack so I will try that to see what happens. I really appreciate the tip. Thanks, Mike

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