Can't Solve 301 Misfire code

Hey all, so I've finally exhausted all of the obvious solutions to my 301 and 300 misfire codes so it's time to ask the forums... Heres whats going on. 2002 V6 4x4 Tacoma, Extended cab, Long Bed, 5 Spd

I bought the truck over 2 years ago with 106k on it, just a baby, and the CEL came on while driving it home from Albuquerque, NM to Steamboat Springs, CO about 6 hours into the 9 hour trip. I got home cleared the code, thought maybe it was altitude going over passes, stayed off for several months. Then in the spring I drove to Moab (5 hours) and the CEL came on again same codes. I took it to a local shop and had the plugs done, CEL came on again about an hour into the trip home. I stopped at oreilly and replaced the ignition coil for cylinder one in the parking lot and drove home no issues. I thought that solved it so I bought 3 new coils and wires to have everything wear together. Then a few months later while driving to Glacier NP (14 hrs) the CEL came back on, took it to a shop, checked compression (fine), replaced incorrect single prong plugs that Moab shop put in with correct double prong ones, CEL turns back on about 4 hours into drive home. Then for about a year and a half the CEL would occasionally turn on and off randomly but usually (not always) when I drove for at least 10/15 miles over 45mph. Had some free time during quarantine the last few months so I replaced all 6 injectors hoping that was the final straw, runs smoother, still got a CEL 300 & 301. I then asked a friend whose a mechanic for advice and he said to check the crank shaft pulley sensor, so I pulled it out, wasnt too dirty, but cleaned it anyway and still getting CEL. At this point I am extremely frustrated and dont know what to do next? My buddy said to pull off the crank shaft pulley to check the tone ring but its a PIA job and kind of a shot in the dark. Is that the next step or could it be a fuse or bad circuit? My right head light burns out about every 8-12 months so I'm wondering if it could be an electrical issue? Please Please Please any ideas on what the next step would be greatly appreciated!!!

 

Test your coils. Search my posts, or find instructions that are out there. Take a volt meter and test the resistances. I'll bet you have a failing coil. I have had one go after 230k. Should have replaced all three but whatever. You did the right thing by starting with the cheap stuff. Though you skipped the coils and went straight at the injectors.

Edit: Did it give you a cylinder?

 

I replaced all 3 coils. I did mention that in the novel i wrote but you must have skimmed over lol. It was second thing I did after the plugs. Yea 301 is cylinder 1 and 300 is multiple misfires.

 

Shit, I missed that...Sorry. I definitely skimmed.

Sounds like a sensor then, because you've done all of the most obvious things. Maybe the crankshaft sensor is just faulty? I doubt a fuse as they just blow out. Could be a loose ground somewhere though. Those can be problematic. I'd start with checking the grounds, then pulling and testing the sensor. Finishing with the most difficult stuff last.

 

the same headlight over and over again... I would think that an over voltage issue would burn out more than just one bulb. They might be connected. If you can put one of those cigarette lighter voltage checkers in the truck and monitor the alternators charging voltage just to see. I had a 2000 Honda Accord that would flash the SRS light intermittantly... no codes to check. The owner then told me that the headlights go dim then really bright sometimes at night. I drove the car a few times and verified the headlight issue, changed the alternator and that "magically" fixed the SRS light too.

the comment about the crank tone ring is something to consider. if you are doing the job pay attention to the break away torque required to take the crankshaft pulley bolt off. If a shop is doing it not sure if they will really care. The issue with these codes, multiple cyl misfire and the specific cyl 1 misfire, is information on what actually sets these codes. I know that there has to be a certain number of misfires before the CEL will be set and I do not know if this year of OBDII has a misfire counter monitor... maybe Mode 6 in generic OBDII might get you the info... then again this could be chasing a rabitt down a hole.

it could be something as simple the timing belt/pulleys worn.

 

Did they do the harness when they did the plugs? I had an intermittent misfire that was caused by a broken plug wire. The CEL and rough running would come and go. I finally got the CEL to stay on long enough to get a reader on it, but it was aggravating til then.

 

Thanks guys, these suggestions should keep me busy for a while.

Yes I replaced all of the harnesses and wires myself. I should also add I have never once felt it misfire, stutter, idle funny, or run anything other than perfectly smooth. Another reason why its pissing me off so much...

Belts and pulleys are all good, thanks for advice on the tone ring, its why i prefer to do the job myself!

 

@OP-

1. Buy yourself a can of quick-start or some such. Cost ya around $3-$4.
   
   
2. Drive home into some shady area where there is no wind (like a garage), open the hood, start the engine, and carefully begin spraying the quick-start as close to the ends of the rubber hoses that connect to the throttle body. Don't mash down on the can's button. Just let a little bit of spray emerge.
   
   
3. If the engine speed increases (even a little bit) when you spray and then over a period of a couple of seconds decreases back to normal I would suspect a vacuum leak at that point, and I would check to see if the hose is clamped. If it isn't clamped I would clamp it and retest. If it is clamped I would check for cracks, aging, etc. at that point. I would also wiggle the hose connection while spraying and see what happens. Could be that the clamp has lost its clamping ability too. Fiddle-fart around with it until you find the problem.
   
   
4. If the engine speed does not increase, move on to the other end of that hose and check there.
   
   
5. If the engine speed still does not increase, then move on to the next hose. Don't forget, two of the hoses (the ones with the big clamps) carry coolant so they do not need to be checked.
   
   
6. When you are done, clear the computer's CEL and commend yourself on saving a bunch of money!

The entire process will take only a few minutes.

I found my leak was coming from the hose connection at the rear of the IAC valve and between the throttle body and the injectors. The hose was clearly on the little pipe but it didn't have a clamp (was that way from the factory). I installed a little radiator clamp, tightened it, retested with another jolt of quick-start, and voila, my CEL has remained off ever since. That was about a year ago. Maybe you'll have the same luck!

 

Thank you for starting this thread. I have been troubleshooting the same exact issue on my 02 4X4 Extended Cab 5 spd. Now issues what you would expect from a misfire code. Truck runs smooth.

I will try this. Hopefully, it is just a vacuum leak. I did recently replace my VC gaskets and sparkplugs. I did not change the wires and coils because they were in perfect condition.

Thank you again.

OP I hope you are able to resolve the issue. It is frustrating for me as well.

 

I am assuming here that you have checked your fuel trims, long and short, using your scanner. If not you are chasing your tail thinking it is one thing when it is something else.

 

I hear you. I didn't think it would work, but it did and I was really happy when the engine rpms increased when I sprayed the area.
Good luck!