Cylinder 3 Misfire

P

PatrickStapler

New member
Howdy folks. Haven't been on here in a while, but I haven't had any problems in a while. Engine developed a misfire on cylinder 3 this afternoon. Ran fine all day. Drove home and parked for about an hour went back out to run and errand, started the truck...really bad miss.

Some background info. I drove the truck to Oklahoma a few months back and it developed a similar miss except it was on cylinder 5. All of the coils were of unknown origin and unknown age...they were not Denso Toyota parts. So I replaced them and the plugs with OEM parts. Problem solved. Truck has ran great ever since...until today.

Plugs, Plug Wires, and Coils are all new and OEM Toyota parts.

What I tested today. Swapped coils 1 and 3. Erased the CEL code. Started engine and within few minutes the code was back. Same position misfire on 3. Pulled everything back out and swapped plugs 1 and 3. Erased the CEL code. Started the engine and code came right back. Same position misfire on 3. Pulled everything back out and did a quick compression check on 3...175psi. Let it sit for 10 minutes, no pressure drop. Put everything back together.

At a loss...all the connections and wires in the looms are in tact and appear to be in good condition. Engine has 295000 miles on it.

Any help would be greatly appreciated.
 
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My last misfire was due to a bad injector. The coil inside went open circuit. Got one off of rockauto. No problems since.
 
I just watched a video that said to lightly tap the top of the injector with a long extension and hammer while the engine is running. Anyone had success with this?
 
PatrickStapler said:
I just watched a video that said to lightly tap the top of the injector with a long extension and hammer while the engine is running. Anyone had success with this?
Click to expand...

Uh I know you can listen for clicking by sticking a long screwdriver against them - you should hear a "click click click".

Sounds like a bad fuel injector. If the code stays on the same cylinder despite all changing all the ignition parts around, it's probably a bad injector.

I also just fixed a misfire on mine - if your misfire is on the passenger side it's a very pain free job to do. All you need are some hand tools and the replacement gaskets/o-rings. There are quite a few posts around here of how people did them and it successfully clearing misfires.
 
check the resistance should be around should be 13.8 ohms but in some cases ohms would be fine but the injector could still malfunctiom. Now test the connector to the injector for voltage. with a volt meter. one contact on the connector is ground so will show 0 volts the other would be 12 volts dc( obviously key on). if this procedure checks out then remove the throttle body, plenum and access the fuel injectors. switch the no 1 injector with anotthe injector put it back together clear the codes by diconnecting the battery or obd scan tool. if the misfire is transferred to the swapped cylinder then the injector is bad replace it with a new oem or aftermarket or refurbished. I've had bad experience with refurbished.
Good luck

Matt's How-to... Blog: How to replace a fuel injector on a toyota 4 runner
 
Thanks for posting guys and the excellent link. I'm assuming now the injector is just starting to fail. I started the truck this morning and it ran perfectly fine. Within a few miles the CEL turned off. Turned off and restarted a few times...ran fine.

A couple of follow up questions, I just did the whole top end and valve cover gaskets job back in the Spring of this year. If I have to replace this injector (#3), can I reuse all the top end gaskets? Seems they should still be fine, but I'm not sure how these gaskets work compared to old cars.

Second question, does all of the upper plenum and throttle body need to be removed to gain access to the #3 injector. Again, asking because I don't know.

Finally, what parts other than the injector are needed when replacing an injector? I have purchased all the parts for this truck from toyotapartsdeal.com and they seem to list several related clips and washers/insulators, but I'm not sure what to buy.
 
spartacus said:
... Now test the connector to the injector for voltage. with a volt meter. one contact on the connector is ground so will show 0 volts the other would be 12 volts dc( obviously key on)...[/url]
Click to expand...

i'm not certain about this, but i'm pretty sure the negative side of the injector is 'floating' and not grounded at that moment. the ground side is wired into a driver in the ECU that pulses a ground for every injection moment while running.
 
DaMonkey said:
i'm not certain about this, but i'm pretty sure the negative side of the injector is 'floating' and not grounded at that moment. the ground side is wired into a driver in the ECU that pulses a ground for every injection moment while running.
Click to expand...

testing the wiring connector to the injector with key on and motor is not running it will be zero on one pin and twelve volts on the other.
 
PatrickStapler said:
Thanks for posting guys and the excellent link. I'm assuming now the injector is just starting to fail. I started the truck this morning and it ran perfectly fine. Within a few miles the CEL turned off. Turned off and restarted a few times...ran fine.

A couple of follow up questions, I just did the whole top end and valve cover gaskets job back in the Spring of this year. If I have to replace this injector (#3), can I reuse all the top end gaskets? Seems they should still be fine, but I'm not sure how these gaskets work compared to old cars.

Second question, does all of the upper plenum and throttle body need to be removed to gain access to the #3 injector. Again, asking because I don't know.

Finally, what parts other than the injector are needed when replacing an injector? I have purchased all the parts for this truck from toyotapartsdeal.com and they seem to list several related clips and washers/insulators, but I'm not sure what to buy.
Click to expand...

the new injector should come with the o rings you should change the crush washers for the fuel rail they are tricky and I lost one of mine part number 90430-12026 this is the part number I used but make sure you check it against the Vin on tpdeal.. you can reuse your plenum metal gaskets.
 
Misfire has MOVED!!!

So I have ran a tank of 87 with a can of Seafoam through the engine. I have all but 50 miles of a tank of 93 with three cans of Seafoam. Problem still persist...but now it has moved. The misfire has moved to cylinder 4. Since 1, 3, 5 are on the passenger side, I assume 4 is on the driver side middle??? I believe this is the opposing cylinder to 3? If the #3 injector is bad, how would that cause a misfire on #4? Is this pointing to something in the harness now? I have not checked the voltages or grounds yet.

Anyway, I broke out the hammer and long extension and lightly tapped all the injectors I could reach...still misfiring. I cleared the code and restarted the engine. Reran the diagnosis...still on 4. The weird thing, is it has ran great every single morning. It doesn't start misfiring until I have driven the truck and it has warmed up, I shut it off for an hour or so and restart, then it misfires.

Any further thoughts?
 
PatrickStapler said:
So I have ran a tank of 87 with a can of Seafoam through the engine. I have all but 50 miles of a tank of 93 with three cans of Seafoam. Problem still persist...but now it has moved. The misfire has moved to cylinder 4. Since 1, 3, 5 are on the passenger side, I assume 4 is on the driver side middle??? I believe this is the opposing cylinder to 3? If the #3 injector is bad, how would that cause a misfire on #4? Is this pointing to something in the harness now? I have not checked the voltages or grounds yet.

Anyway, I broke out the hammer and long extension and lightly tapped all the injectors I could reach...still misfiring. I cleared the code and restarted the engine. Reran the diagnosis...still on 4. The weird thing, is it has ran great every single morning. It doesn't start misfiring until I have driven the truck and it has warmed up, I shut it off for an hour or so and restart, then it misfires.

Any further thoughts?
Click to expand...

Not really, you are just a lucky bum who happened to get multiple misfires. My bet is that if you keep driving the #3 code will pop up, along with the P0300 Multiple Misfire code.
 
PatrickStapler said:
It doesn't start misfiring until I have driven the truck and it has warmed up, I shut it off for an hour or so and restart, then it misfires.
Click to expand...

This is a very common failure mode for these injectors. If you do a search on the forum, you will find many threads stating exactly the same thing. Coil in injector gets hot after you shut off the engine & gas flow stops, then it goes open....cools off and continuity is temporarily restored.

Buckaroo
 
Last edited:
A lesson I learned when I was younger: Just because a part is new does not mean it is good. Sounds to me like that coil for cyl 3 and 4 is bad. If you still have your old coils use one that you never had problems with on 3 and 4. Also check the wiring coming into that coil. If you have a bad input signal you will have problems with the output even if the coil is good
 
St Runner said:
A lesson I learned when I was younger: Just because a part is new does not mean it is good. Sounds to me like that coil for cyl 3 and 4 is bad. If you still have your old coils use one that you never had problems with on 3 and 4. Also check the wiring coming into that coil. If you have a bad input signal you will have problems with the output even if the coil is good
Click to expand...

I previously swapped the new coils and plugs between 1 and 3 and the problem stayed on 3.
 
But your problem then shifted to 4. The odds of the injectors being bad on 3 and 4 are a lot less than the odds of the coil being bad for 3 and 4. I think you should start checking the input signal to the coil as you have pretty much ruled out the coil itself being bad.(three separate coils with the same problem are low odds) Swapping out another ecu is also another test you can do (they are pretty cheap used for the auto)
 
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