Misfiring Problems at 70 + mph
 

Hey guys I'm new to the forum but I'm having problems with my 99 4runner 3.4l 4x4. When I'm driving and getting up to speed on the highway 70mph + I'm getting misfire codes. The misfire is cylinder 5 and 2. I've already replaced the coils wires plugs and changed the injectors and fuel filter. Can anyone help please if they have had the same problem.

Thanks Randy

What codes are you specifically getting? P0305? Anything else? Mileage? Coils plugs wires, injectors, fuel filter all replaced when? And with what aftermarket or OEM?

It has on the frame 343000 a lot but the engine has 120000. I replaced the coils plugs wires injectors with oem the beginning of this month. And the fuel filter is one from oreillys not sure the brand.

Thanks Randy

Also P0305 and P0302 are the codes and the light only come on at 70

https://repairpal.com/OBD-II-Code-P0305

Are you driving with any other symptoms? What's the history with that 'certified pre-owned' engine? Any timing belt work recently? CEL isn't blinking and just comes back on at high speed right? No P0300 right? 'Cause if there is, that could mean all the stuff for the rest of the cylinders that you did for 2 and 5.

Strange how your misfire codes happen AFTER you replace a lot of the usual suspects.

I doubt it be vac leaks, or MAF issues, but it be simple things to check/clean. Fuel pressure I doubt. But you could check. Compression check also another good way to check the engine.

Or as the link also suggests, can be caused by other drivetrain-related components.

Good luck

Sorry that all was happening before I changed all parts. Only reason I changed them was because the Toyota dealership said first it was the coils plugs and wires. Then they said it could be the injectors so I replaced all 6.

I'm not sure about when/if the timing belt has been changed. All of this just recently started about a month ago. When driving it there's no change in rpm when the light comes on it just flashes and goes off.

The engines doesnt use use oil and every time I change it it's still clear looking. I'll probably be doing a compression test this weekend.

Thanks Randy

And no other misses just 5 and 2.

If it were my runner, I'd double check their work. No offense to those. I just prefer to see it myself.

CEL blinking is a whole different kind of misfire than one that comes on and stays on. From what I read, you're saying yours comes on and then goes off...quickly or after awhile?

I mention timing belt because I've read how other's misfires came on because of loose crank/cam position sensors...even the crank pulley bolt. But that be just guessing. You could check the timing marks and see if they still line up. If they aren't, that may be another possible explanation.

Thanks for all the help I'll check those other things or just not drive it on the highway anymore. Lol.

If it does blink on and off, definitely dont drive beyond 70 continuously.

If you have any updates, please do share.

One tool I'd recommend is a scan tool that can give you some detailed info on the actual running conditions of your runner. It is pricey but can pay for itself with the money you save from bringing it in for diagnostics. It can help narrow down the search for the faulty or failing part.