Deryck

I have a V6 98 T100, the engine started lagging as if it wasn't getting enough fuel, it was a like a quick stall. The engine light started blinking, so, after noticing the dash indicators were normal I pulled over to look under the hood. I didn't hear abnormal sounds so I closed the hood, got in, and the blinking was gone. The engine was still doing this lagging and when I hit 50 mph on the interstate the light went solid. Went to Schuck's did the diagnostic and got a P303 misfire code. Checked sparkplugs and their gaps they all seemed fine any ideas before I spend the $60 on a running diagnostic.

ImportBuilder

Check all of your plug wires, and the rest of the ignition system.

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OSUCowboy27

P303 means misfire on cylider #3

I had several problems with misfires on my '98 3.4L. It has a weird ignition system. One coil produces spark for 2 cyliders. The 3 coils are on the right 3 spark plugs and 3 wires run from the coils to the left side of engine.

You might try swaping the coils on #3 and #5 and see if the misfire is still on #3. If it still says P303 then you need to change the plug or there is an injector issue. This will rule out coil and the expesive coil boot. If it says P305 then I would change the boot and if it continue, change the coil. If it is time, I would change all the plugs (use only Denso or NGK) and change the 3 spark plug wires. Make sure to use plenty of boot grease. Hope this helps and BTW, if it is the coil and you purchase a new one, it will be about $75 and it comes with a new boot. The boots run about $17 and it is a good idea to have an extra.

Toyota Kid

A common problem on this make/model/year. If the diagnostics can't help ypu id the problem, and you don't have the $ to let a certified Toyota tech proerly evaluate it, then I would recommned just driving the vehicle until you have concerns, then trade it in on a Chevy.

Toyota-Kid
Certfiied TMC Master Mechanic