yellowtoytruck

Hey guys,

I do not have a truck in this forum range but my engine is from a 99 4runner so I decide to start here. Basically what has happened is that I recently did a few things to my engine and now I am getting the following codes
1. P0300 - Random / Multiple Misfire Detected
2 .P0301 - Cylinder 1 Misfire
3. P0305 - Cylinder 5 Misfire
4. P0306 - Cylinder 6 Misfire

A little history of my engine work. The truck was running fine and great. Its an 85 Pickup with a SC 3.4. I was getting knock sensor codes so I finally decided to tear the engine apart to get to those. I replaced those and put the engine back together. While putting the engine back together I installed the URD 7th Injector kit as well as their 2.2" Pulley for the supercharger.

What I have done so far.
1. I do not think it has to do with the 7th injector kit because before I spliced into the wiring harness and did the final wiring instll for the kit, I had did a test run with just the smaller pulley on the SC and thats when I first noticed the codes. I finished the installation of the wiring and the codes remained and come back after clearing.
2. I replaced the spark plugs with new ones and the problem has persisted.
3. I checked my coil packs. CYL 1 Primary was 1.0 OHM, Secondary was 12.7. CYL 3 Primary as 1.1OHM and Secondary was 12.7, CYL 5 primary was 1.0 OHM and secondary was open. Replaced coil pack on CYL 5 and nothing changed.

I can still drive down the road and get to highway speeds. Truck has steady idle. But I can hear the slight hesitation on take off.
So as of now I do not know where to look next. Any ideas?

UPDATE:
UPDATE

After listening to some comments and some advice from friends I have done the following
1. Cleaned the MAF sensor and put back in. No change that I could tell.
2. Swapped CYL 1 coil pack with the one removed. When I did this only the P0306 code became logged with the rest pending.
3. Swapped CYL 1 coil pack with the new one that was installed on CYL 5. Went for a much longer drive including some highway. When I returned no codes were logged. However, all the original were pending.

TheDurk

First, what plugs did you install? These engines are picky. Should be Denso or NGK dual elements. 1.1mm gap, checked with a wire gauge.

Then, pull each plug and look carefully at each one. Compare 1, 5, and 6 to the others. Unburnt fuel? Oil? Burning? Discoloration?

Probably not spark generation as you managed to get one plug from each of three different circuits.

So checking injectors electrically and with a stethoscope and a compression check may be called for.

yellowtoytruck

I got Densos. All of the plugs when I pulled and inspected them looked fine.

vasinvictor

iTrader: (3)

How many miles on 5vz? Injector are known to start failing around 250k...

Pozi

I chased the misfire on my 2000 Taco for a long time...too long in fact. Indeed it was an injector. Cheapest place I've seen for OEM rebuilds is Rockauto. I recently put el cheapos from ebay in mine and it's been running great so far.

atcfixer

iTrader: (1)

I have a T100 with a mis fire (only cyl 2), and based on my research, nearly every thread ends with a bad injector. They should ohm out around 15 ohms (I think the service limit is like 12-25 ohms). The suggestions I've seen were, plugs (double ground strap NGK or Denso), MAS cleaning/testing, TPS test/adjust, IAC cleaning, new wires (when related cyl is on a spark plug wire), and I'll add in possible igniter, wiring, or ecu.

If you were driving and all of a sudden multi cyls are causing a misfire, I'd point at what is in common with them.... the igniter and of course replace the tested bad (open) coil. From there I'd ohm wires from igniter to ecu and injectors to igniter. This is all assuming you're running OEM plugs, good wires etc. Another tip about checking the wire, also check for corrosion and loose/damaged pins. Toyota uses good quality wire and terminals, so wire problems are pretty unlikely, but if the truck is rusty, it could have a rust hole in the front passenger side wheel well which is right where the ECU is located. That's exactly why my T100 had a failed ECU, the 3 bad coils and igniter is because of me plugging in an AT ecu in the MT harness w\o checking the pinout first lol. Unsure if that relates to my bad injector or not.

Good luck!

vital22re

iTrader: (2)

you should be running ik22 denso plugs with the supercharger. 3.4 will crack heads so that could be it. Do you have an air leak somewhere? If you are running a 99 engine, you have brown plastic injectors but are you running a 99 ecu as well?
Is your 7th injector kit working properly? are you watching the AFR? How are you long term trims and short term trims? get a scanner with live data and monitor those. They help you understand if you're running lean and causing a lean misfire.

elosha

hey guis my engin(3.4vz-fe) is missfiring when it's getting warm when I drive about 100km, I chacked coils, sparks, fuilpump, airfilter, and all is good, what could be a problem?

atcfixer

iTrader: (1)

Ohm the injectors, there's a way to do it at the ECU connector, but you need the correct pins, shoot me the year and model and I can get the pins and wire colors.

To update my last reply, my 98 T100 with the mis on a single cylinder was in fact a bad injector (high ohms). Bought 6 refurbished injectors and besides some issues with the o-rings not sealing, the engine runs great again.

sox375@gmailcom

Hey guys, I have a stock t100 sr5 3.4 and a misfire on cylinder 5. Went through it and checked the injector wiring with a noid light .got nothing injector and coil have been replaced . Am I looking at a bad driver in E.C.M.?

atcfixer

iTrader: (1)

No clue what year you have, so I pulled up 98. Also there's different diagrams for auto vs manual, I'll pull up the manual. Injectors should have power on black/red wire, the ECU grounds them to kick them on. #5 comes up as white/blue wire. I'd say get a long extension and check the white/blue wire if it connects from injector plug to ECU plug (pin 6). Different options/years might be a different color/pin. Assuming the noid light test is 100% getting connection etc you issue should be between wiring or ECU. Also the ECU generally grounds to the intake manifold on a lot of models, make sure that's hooked up, might get poor signals if not. According to the wire diagram, the injector wiring for the ground side goes directly to the ECU, no splices, no connectors. Power side (all are spliced together) comes from the ignition switch and does go through one connector, but that connector would effect all injectors. Still test for the +12v on the black/red wire though with key on.