1996 tacoma 2.4l 2wd 180,000 p0300 - random misfire

nickn · 12-14-2012, 01:07 PM

I am looking for suggestions on what to try next with my truck. It put out p0300, random misfire, and p0301-304, misfire on all cylinders. It started out misfiring worse at idle, and it was fine above 40 mph. after changing plugs, plug wires, coil, rotor, distributor cap, it idles fine, and now starts to misfire around 1700 rpm. it will stop if i accelerate in first or second past 2500 rpm, but 3,4, and 5 it gets worse the more i accelerate. I also replaced the fuel filter. could it be throttle position sensor or would it be putting out a code for that? How about the ignition module? thanks for your help.

nickn · 12-16-2012, 01:24 PM

replaced ignition module and patched crack in exhaust manifold its better, but still misfiring a little.

tacomatic1 · 12-16-2012, 01:28 PM

i was getting bucking and misfire when cruising/slow accel around 2500 rpm when my front O2 was bad. Changed it and it went away. This is because your truck uses the front O2 for cruise AFR/slight throttle. Under high throttle it uses the fuel table.

Enola Gaia · 12-17-2012, 07:08 AM

(1) Welcome to CT, nickn!

(2) I think you're the 3rd one in the last month to ask about misfire problems in an early (1995.5 / 1996) 4-cylinder.

(3) It's conceivable that a problem with the throttle position sensor could cause this. So far the only solid solution anyone's found has to do with the front O2 sensor and / or the wiring associated with the front O2 sensor. Whether this turns out to be the source of your problem is anybody's guess.

nickn · 12-17-2012, 08:38 AM

thanks guys, i will give that a try.

nickn · 12-25-2012, 12:25 PM

well i ordered the front o2 sensor, and the day it came in my check engine light had come back on, i went ahead and put the o2 sensor on and drove the pickup, still misfires, mostly in 4 or 5th low rpm and then giving it alot of gas, and the check engine light was still on. so I put the reader on it again and this time it read p0141 oxygen sensor bank 1 sensor 2, which is for the one after the cconverter. could this sensor have anything to do with my misfiring problem, or did the misfiring cause this sensor to trip the check engine light? thanks for your help

tacomatic1 · 12-25-2012, 07:22 PM

i highly doubt sensor 2 would cause a misfire, as this one is merely for indicating whether your catalytic converter is functioning. Have you cleaned your MAF recently? Also did you pull the efi fuse or disconnect the positive for a bit to discharge the ecu?

NVTACO · 12-25-2012, 09:01 PM

Any modifications?

Try checking the compression and valve clearance

nickn · 12-26-2012, 07:43 AM

Cleaned MAF last week, i didnt disconnect battery after replacing front 02 sensor, but i did after doing the other work. And no modifications to the truck. I will try disconnecting the battery one more time. I may take it to a mechanic if i need to check compression and valve clearance.

TeamSleepRacing · 12-26-2012, 02:34 PM

You say that all the "tune up" helped curb the missfire a little? Could be related directly to the distributor itself. Pull the cap back off, grab the rotor shaft firmly and try to wiggle it(side to side, circular play is ok).If the shaft has Any play in it at all it will make it missfire a bit.

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