P0302 Help Needed...

[myoldtoy]

Hi Guys,
My friend of 15 years started running a little rough about 3 weeks ago but only briefly. Most of the time it's been running normal but this week it's been on and off more often. Best I can describe is that it's more like a stumble. It can work it's way almost out while driving, only feeling a stumble once in a while. Then I might stop to run in a store, get gas or something and right upon restarting it starts to really skip or stumble.
This morning on my way down to Hatteras she was stumbling for quite a few miles with the eng. light blinking on and off. Eventually the light just stayed on even on restart. On my way home today I stopped in a brand new Auto-Zone store here in Kill Devil Hills and asked the guys if they could plug a code reader into the truck and tell me what code has been thrown.

P0302 - #2 cyl. misfire, plugged injector, mech fault, vac leak at #2 are all what their computer says the problem could be.

150,000. miles on the truck. 55,000 miles on the Toyota spark plugs. Engine runs excellent up to this point. Been threw a few tanks of gas.
The stumble feels like when an O2 sensor went bad about 60,000 miles ago.

Really could use your thoughts and input to help me get this resolved.
Thank you in advance Guys!

 

[HCurphy]

plugs, wires, coil pack, injector. in about that order.

switch a coil pack from another cylinder first, its free, and see if the misfire follows that coil pack to another cylinder.
If it doesn't change plugs.
still missing? change wires.
still missing? test injector or run some injector cleaner

edit: since you're not getting P0300(multiple cylinder misfire) it's most likely something specific to that cylinder and not a sensor

 

[myoldtoy]

Thanks for the reply.
From all the threads I've read on the P0300 series codes all of the above are likely culprits. Seems like injector issues are most common???

What gets me is that on stone cold startups the truck runs great for a long while. Obviously the plug, wire, coil, and injector are just fine. I shut it off, go do something, come back and start it up 5 minutes later and immediately it's stumbling again! What gives with that? Why does this only happen at normall running temperature and not when cold? There has got to be a little science that can explain this behavior.

I liked it better when I threw the O2 sensor code. Went and bought a new one, popped it in and all was good. To bad this issue isn't as simple!

I need a thread showing how to swap out injectors on these motors.
I'm not even sure which is the #2 cylinder!

 

[TheDurk]

Thanks for the reply.
From all the threads I've read on the P0300 series codes all of the above are likely culprits. Seems like injector issues are most common???

What gets me is that on stone cold startups the truck runs great for a long while. Obviously the plug, wire, coil, and injector are just fine. I shut it off, go do something, come back and start it up 5 minutes later and immediately it's stumbling again! What gives with that? Why does this only happen at normall running temperature and not when cold? There has got to be a little science that can explain this behavior.

I liked it better when I threw the O2 sensor code. Went and bought a new one, popped it in and all was good. To bad this issue isn't as simple!

I need a thread showing how to swap out injectors on these motors.
I'm not even sure which is the #2 cylinder!

Since the invention of battery ignition, coils have tended to fail when hot but work fine cold. This is usually due to softening of insulation and the fact that the winding expands as it heats up. This is why we always recommend a coil swap when diagnosing single cyl misfire.

A similar thing can happen with plugs. You have a crack in the porcelain insulator and it gets wider when the plug gets hotter. With 55k on the plugs, any mechanic would start there. Period. Since plugs and wires are cheap, one tends to do those first before injectors. I'd really hate to do an injector swap and come back and find it was a wire or plug all along. I am sure I would only do that once--if I did it at all.

How old are your wires? If they are Sumitomo with the year on the wire, they are original and need to be changed anyway.

He had it right:

plugs, wires, coil pack, injector. in about that order.

But here are some how-to's:

Fuel Injector Removal Pictures (How To) - YotaTech Forums

Matt's How-to... Blog: How to replace a fuel injector on a toyota 4 runner

Also, save this--I have a feeling you are going to need it:

 

[jkoni426]

55,000 miles on the Toyota spark plugs.

that's my vote for your problem right there. plugs should be changed every 30k miles.

 

[myoldtoy]

Thank you to "The Derk" for a very imformative reply! And there was some of the science as well as that diagram that I have been looking for. I didn't even have any idea which cyl. #2 was!

You all might find this funny but I didn't change the original spark plugs until the truck had about 92,000. miles on it. They were melted when I took them out but the truck still ran great. It was a Toyota mechanic that told me I'd better get the timing belt changed as well. He said that I should have done that @ 60,000. miles?!
I've owned 4 brand new white 4x4 Totota trucks since 1980. These have all been my DD's. Before that I bought a brand new Datsun PU in 1974. All of these have been so reliable that I get spoiled and I forget about doing some of the less obvious maintainance items. Oil changes at no more that 4000 miles was always important though. Seldom driven hot rods that I have owned always got preferential treatment when my DD's were taken for granted. Sad huh!

I'm going to send for some new Denso's and coils right away.
Thanks Guys, Bob

 

[TheDurk]

Thank you to "The Derk" for a very imformative reply! And there was some of the science as well as that diagram that I have been looking for. I didn't even have any idea which cyl. #2 was!

......

I'm going to send for some new Denso's and coils right away.
Thanks Guys, Bob

You're welcome.

I wouldn't spend for all new coils. Just swap the coil on cyl #2 with one of the others and see if the misfire moves with it. If it does, replace that coil. We wouldn't want to spoil that truck by going overboard on maintenance.

 

[shadow247]

Here you go...