Hello,

I have a 1998 4x4 4runner with 240,000 miles on it.

I have used this forum for a few years now and typically have found the answers i was looking for here without needing to post. You guys know your stuff.

This time i am in a different situation. I am in Chiapas Mexico and i speak mediocre spanish. My problem started with a check engine light back in San Diego. I would get a stutter between 1500-2100 RPMs only while in overdrive. I got the code P0120(faulty TPS) and handled the repair. After a few weeks on the road, i began to get the stutter again. I read up on the issue and finally decided to replace the spark plugs. They have an Autozone down here and i tried to get NGKs, but they only had Bosch and few brands. I bought the best ones they had, dual ground Platinum 2+, and had them replaced since my tools are back at home. I drove away and the vehicle felt fine until i began going up a very steep grade for about 1 minute at which time the vehicle started to misfire. The check engine started to blink only when the vehicle downshifted to make it up the hill. I pulled out my code reader and got a P0304(cyl 4 misfire). Back to the shop. After 4 hours of them testing, they could not figure out the problem. We were headed for Guatemala and now are stuck in Chiapas until i get this issue handled. Any advice would be greatly appreciated.

 

Did you change the spark plug wires? Could be the fuel injector is giving up.

 

Misfires can be from a few different things, plug could have been dropped and either the gap is not in specs or the porcelain could be cracked. You can also get them from bad O2 sensors, failed or clogged injectors, bad fuel, valves that are out of adjustment. What does the freeze frame data say for the code? Like rworegon said, did you change the plug wires? Are the boots all the way on?

 

I did not. That is the next step tomorrow. Just curious, why would my wires give out at the same time my plugs were replaced?

Down here they test each wire and plug separately by starting the vehicle and pulling the wire and plug out of each cylinder and seeing if it produces a spark against the manifold. The 4th cylinder does produce the same amount of spark as each other cylinder...don't know what that means to us gringos, but i found it interesting.

 

If the plug wire was just yanked off it will tear the wire, it will throw out a spark but will arc out instead of going through the plug. A better way would be to ohm check the wires. Also, you can have a misfire code for cyl 4 but it could be a misfire on 4's paired cylinder because the engine uses a waste spark method which means that when cyl 4 spark plug fires that cyl 3 also fires at the same time although cyl 3 is not using the spark to do anything. (I am not positive that cyl 3 is the other cylinder to 4)

Also you could try swapping coil packs with another cylinder and see if the misfire moves, coil packs rarely go completely out and are usually intermittent from what I have seen.

 

Get rid of those bosch plats and get a standard style electrode style plug and i bet your problem will go away. For some a lot of engines do not like the 2prong or 4 prong style plugs such as the bosches.

 

+1
The Bosch's center electrode is too small. Read up on wasted spark ignitions and you will understand why. A cheap standard plug will work better.

The orignal studder may have been a dirty or failing fuel injector.

 

+2. Throw the Bosch plugs in the trash. Get some NGK part # 3967 (BKR5EKB-11). Problem solved.

 

I will do. I just spent 2 hours reading up on another forum about a burnt valve and now am stressed out. Hope the easy fix saves the day, but at this point, tempering the expectations.

Thanks for the replies, and i'll update you fellas ASAP.

 

I know the OP was long, but in there i mentioned that I can not find NGK plugs down here in Mexico. Any other suggestions?

 

Any spark plug that looks like this




According to your orginal post you are running these These plugs always seem to cause misfire codes to pop for some reason.

 

Well, U obviously have access to the interwebz, so just order some from partswarehouse.com or something like that....

Also, from my experience with these motors, they DO prefer the NGK dual electrode plugs... I have seen a couple just run like poop with the standard single electrode ngk's, and just throw your $ in the garbage if ur gonna buy bosch, or better yet, send it to me

 

^Agreed, it says right under the hood to use dual electrode plugs.

 

First off, Team 420, have you ever been to Mexico before? It's not like they have UPS running around the dirt roads here delivering stuff you bought from the internet on a days notice. However, they do have some cheap 420!

Thanks to everyone for the advice. I searched high and low for a mechanic down here that had a diagnostic scanner. It was throwing off P0300-301-302-304 and P0120. It turned out that the plugs were not the issue. It was the cables after all. One of the rubber sheathings were split but not visible, however the charge could make it out of the side and it was not reaching the plug. I hope this helps someone.

Again, thanks fellas.

 

Plug wires for the win! Thanks for posting the resolution.

 

Sounds like you found the issue. I was getting the same p0300 codes on my taco. After spending 2k and the stealership i re-gapped my NGK's and now it runs like its brand new.

 

You should still go back to the recommended BKR5 plugs. You will burn the tabs off non stock ones eventually. The left bank of cylinders runs reverse polarity due to sharing the coil with the right side. This erodes the ground straps. You can also use Denso IK16 plugs if you are not supercharged.

 

Layhammer,
I'm getting almost the exact same codes; P0120, P0300, P0305, P0304, P0303. And I just failed an emissions test to get my tabs renewed, so I need to get this fixed quick. I am going to try wires and plugs and see if that fixes it.