I wanted to post this to maybe help some of you out or at least maybe point you to a possibility. Also, share some findings.
On our 2002 4runner with 280K miles, it started to develop a misfire a few months back. Totally random. Could be at a stop light, or driving down the freeway. It was very hard to catch or diagnose. Down the rabbit hole we went! These are the findings.
- Had received a counterfeit set of iridium plugs from amazon. Never gapped them, but all 6 had missing iridium tips. The tell was the screw on terminal vs. fixed dark gray terminal on authentic NGK. Some say OEM dual ground electrode only, nope. Hundreds of thousands of miles on my other 4runners will argue that point... but anyways. Replaced with authentic NGK iridium and hoped the issue was gone. It helped big time but was not the problem.
- Wires were NGK and had around 80K on them. Went ahead and replaced the set as the boots on the drivers side bank were damaged a bit as my son pulled on them a little hard and damaged them. Not the issue.
- I found an issue when testing the coil packs that I was SURE was the issue! Pulling off the rubber boots to get to the inner brass terminal, 2 of the 3 had heavy oxidation / tarnishing. So much so I thought they were rusted. This is an AZ car so that is odd. I could not even get a reading on my multi-meter. They were dark, dark rust brown. The small pin side spark plug wire connector was also really bad. I used scotchbrite to scrub off the mess and clean all terminals best I could to get a reading and all tested good finally. I did end up replacing them with new denso since they are about $60ea for good measure. Another improvement overall but was still getting occasional misfire codes and shudder.
- Fuel pump had been proactively replaced with filter in the last 4-5 years with denso / wix. Not suspected but something I was thinking about.
- Never a code for a crank position sensor or any sensors. Just a misfire code, was rather random on different cylinders and not related to coil pack / wasted spark plug combo. And yes, you could feel the drop in power when this happened or a shudder.
- Went through every vac line which I had kept up and all good and checked intake and valley gaskets for leaks as well as injector seal areas for leaks. Nothing. Idle air and TB clean as it gets.
- For good measure, ran a compression test and it was beautiful IMO. All at or around 195 with one slightly under 190.
- So at this point since the code and feel was so random, I decided to pull the injectors and test / refurbish them. All injectors ohmed out fine. Ultrasonically cleaned them all. Used my amazon injector pulse tool and all sounded excellent. Used the tool with TB cleaner and spray pattern looked good. Put back in our cleaning solution and let pulse for about 15 minutes each, while listening to the injectors. Sounds perfectly fine, never a skip or pause. No issue here I thought so put new seals and o-rings on and sent her off again. And again... random misfire a day later.
RESOLVED: About to totally flip my lid and a bit at a loss I started to focus on those old injectors as just something to replace to rule out. I called a local company called AUS injection that really knows their stuff (used them for years). Speaking with them, they stated the arrow (I think it was arrow) odd brand injectors toyota used for a short bit were well known for this (Random issues at higher mileage and rando misfires or locking up) They could check them, clean them and put through their refurb process (already done by me) at $25ea but would not guarantee them at all. They did not even want them as cores as they feel they are junk. I trust what they were saying as the guy was not trying to sell me anything. He recommended I buy
denso replacements part number 23250-0A010 and to use those and get rid of the others. I asked him if he had them in stock as I needed them straight away. He did, ran down and picked them up.
Here we are nearly 3 weeks later. Engine is smooth as butter, starts WAY faster and NO Codes! It was those damn injectors this whole time. Maybe, this helps some of you in a similar situation.
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