Just joined and this is my first post. In 19 years of ownership this is the first time my Taco has given me cause to take to the internet in search of solutions. I've got a problem that's really got me stumped so here I am to prostrate myself in front of the oracles and pray for advice.

First things first:
2002 Tacoma SR5
2.4L four banger (2RZ-FE)
Bone stock.
284,000 miles
I've owned it since brand new and made no modifications.

The problem:
This started about a month ago. When I left my house and started driving once I hit about 3000 RPM I started getting a jerky hesitation feeling from the engine. As if at least one cylinder was misfiring occasionally. The problem continued enough that I took it back to the house and got in my wifes car. The next day I got in the truck and the symptoms did not come back. The day after that they returned. This continued to happen on and off for a few weeks but with increasing regularity. One day as soon as I started the truck it began idling very roughly and the CEL began to flash. I was only a few miles from home so I started down the road with it running very rough, very obvious misfires. About half way home the engine smoothed out and it ran as normal. The problem has been very intermittent. For a week or two it would start and run great until the first time I stopped and shut off the truck, as soon as I restarted the truck it would begin running rough/misfiring again. I started troubleshooting it myself, figured I had a fuel issue. I changed the fuel filter, no help. I checked the fuel pressure and found it a little hit (about 47 PSI) so I changed the pressure regulator.Truck ran great on a 5 mile test run and ran great the next day until I shut it off at a gas station and then ran rough as soon as I started it. I got frustrated and finally took it to a shop. They had it for several days before calling to say that they got a code for the #2 fuel injector, swapped that to another cylinder and the problem followed so they changed the fuel injector. Now the running rough and misfiring seems to be gone, no CEL but I still have the 3000 RPM and above hesitation/stumble.

Recent maintenance:
Coils less than a year old
Three fuel injectors about six months old and one brand new one
Spark plugs about two months old
Fuel filter one month old
New fuel pressure regulator
Compression checked by me and the shop. Can't remember the numbers but it was good.
PCV less than six months old
Bank 1/Sensor 1 FA sensor about two months old. (changed because of CEL and corresponding code)

Truck now has a fresh tank of fuel with some injector cleaner in it just to see if it makes a difference.

I'm an aviation mechanic so I'm fairly mechanically inclined but this one has me really stumped. I'm thinking my next steps are probably to check resistance on the fuel pump even though it seemed to be providing plenty of pressure.

Help me Yotatech, you're my only hope!

 

A flashing CEL is usually multiple cylinder Misfire of the P03xxx variety, which would also include a code P03xxx of the offending cylinder(s). There is no a CEL for "bad injector", Bad injector circuit or circuit malfunction yes P02xxx, which Could be a bad injector, not a common CEL to pop up. These brown plastic injectors have been giving people problems, even using the FSM won't prove the resistance is off as it seems to get flaky with heat or dampness, and then return to normal operation, but can be used to narrow down the problem without throwing parts and money at it. But your description is similar to the x2 3rd Gen 4R's I fixed by replacing 1 or 2 injectors in each case. If we knew what codes you where getting that would help, it may take awhile for pending codes to show up, but I'm guessing you will eventually get another p03xxx misfire for a specific cylinder, perhaps one of the replacement injectors are faulty, maybe check continuity from injector harness to ECU. These can be a PITA to trace down.

Pre 99' injectors don't seem to be effected by this problem, if I have this issue on my 99' I might just swap all them out for the OEM old style. I also advised the other owners to swap all the injectors and be down with it, they opted to do one at a time, in one case it worked out, in the other case we had to do the job twice.

 

Thanks for the reply. Sorry, I forgot to include the codes that I and the shop read.

When I was working on it and the check engine light came on I got the P0300 "Random Misfire" code. Occasionally I also got a specific P03xx for one or more cylinders but it never seemed to be consistent. Sometimes it would be one cylinder and sometimes another.

The shop said they got a misfire for cylinder #2, I assume a P0302. They said they also got and injector code for cylinder #2 but I'm not sure exactly which code that was but that once they swapped the #2 injector to #1 cylinder the code followed to #1 cylinder.