Missfire Cyl#2

[Crackership]

Hi all,

I recently purchased a 1996 Limited with 260k on the clock. I got it for a steal with a P0302 CEL for missfire cylinder #2. I've read every thread I can find that might help, but I've still got the missfire. I'm hoping someone can point me to something I've overlooked.

Here's what I've done so far:

- checked all the vacuum lines, some don't look great but no apparent leaks
- cleaned the MAF
- replaced the spark plugs (yes, got the correct 2-prong guys)
- replaced spark plugs wires
- replaced the coil for 5 and 2
- cleaned the throttle body and IAC
- Bench tested the IAC and it checks out
- replaced injectors

The only things left that I can think of are compression test and then check the timing. Any other ideas?

TIA!

 

[LittleCaesar]

Perform a compression or leak down test to get an idea of the physical health of the engine. The latter would be better.

Any coolant loss?

O2 sensors look original?

Check all the grounds as well.....

 

[thegipper]

Perform a compression or leak down test to get an idea of the physical health of the engine. The latter would be better.

Any coolant loss?

O2 sensors look original?

Check all the grounds as well.....

Leak down test is needed, it's the gold standard on checking the engine for major issues.

 

[Crackership]

Perform a compression or leak down test to get an idea of the physical health of the engine. The latter would be better.

Any coolant loss?

O2 sensors look original?

Check all the grounds as well.....

I'll do a compression test today.

No coolant loss at all.

The O2 sensors look original or, at least, very old. But I would think more of a general fueling issue would present with a bad O2, rather than a single cylinder miss. Is there something I'm missing there?

I've been checking every ground I find, is there a diagram of their locations that you're aware of?

Thanks!

 

[spartacus]

I'll do a compression test today.

No coolant loss at all.

The O2 sensors look original or, at least, very old. But I would think more of a general fueling issue would present with a bad O2, rather than a single cylinder miss. Is there something I'm missing there?

I've been checking every ground I find, is there a diagram of their locations that you're aware of?

Thanks!

Ground point diagram

 

[Crackership]

Ground point diagram

Thank you!

 

[LittleCaesar]

I'll do a compression test today.

No coolant loss at all.

The O2 sensors look original or, at least, very old. But I would think more of a general fueling issue would present with a bad O2, rather than a single cylinder miss. Is there something I'm missing there?

I've been checking every ground I find, is there a diagram of their locations that you're aware of?

Thanks!

Usually that is the case with 02 sensors, though in a blue moon I have seen a lazy one cause such, though it is usually mated with a PO300.

Post up your numbers when finished. As [MENTION=138943]thegipper[/MENTION] alluded to, a leak down test takes away all guesswork.

 

[Crackership]

Usually that is the case with 02 sensors, though in a blue moon I have seen a lazy one cause such, though it is usually mated with a PO300.

Post up your numbers when finished. As [MENTION=138943]thegipper[/MENTION] alluded to, a leak down test takes away all guesswork.

I'll do a compression test today. I don't have a leakdown tester, but I'll see if I can cobble something together with the hose form the compression tester. Is there a way to get the timing covers off enough to verify TDC without removing the upper radiator hose? I'm guessing not, but I can hope.

 

[Bad Luck]

I'm not sure if your year has it, but you may see if you have an igniter module. When I was dealing with my 4Runner misfire I diagnosed that module some to verify operation. Something to consider.

I'd also ohm out all your coil packs on the primary and secondary circuits.

 

[JohnMc]

Is it noticeably running on 5 cylinders? Only at idle or accelerating/higher PRM's as well?

It takes a fair amount of compression leak to show up as a miss. SO much so that usually a 'shade' tree compression test can spot it.

Pull the wires on all three coils, then crank the motor around for a short bit. So you don't flood the motor with gas, just do it a few times round and round. And listen as the start labors over each compression. Whir, whir, whir, whir... LIsten for any spot int he cranking where it sort of sails on by a compression without slowing down (as much).

Easy, quick to do, no tools needed, and if you hear uneven cranking, then yes, you've got big problems and will need to do more diagnostic work. Leakdown tests are great because they tell you where the compression is going. Out the PCV system - bad piston/rings, maybe a HG. Out the cooling system, probably a bad HG. Out the intake or exhaust, something wrong with a valve.

 

[Crackership]

Is it noticeably running on 5 cylinders? Only at idle or accelerating/higher PRM's as well?

It takes a fair amount of compression leak to show up as a miss. SO much so that usually a 'shade' tree compression test can spot it.

Pull the wires on all three coils, then crank the motor around for a short bit. So you don't flood the motor with gas, just do it a few times round and round. And listen as the start labors over each compression. Whir, whir, whir, whir... LIsten for any spot int he cranking where it sort of sails on by a compression without slowing down (as much).

Easy, quick to do, no tools needed, and if you hear uneven cranking, then yes, you've got big problems and will need to do more diagnostic work. Leakdown tests are great because they tell you where the compression is going. Out the PCV system - bad piston/rings, maybe a HG. Out the cooling system, probably a bad HG. Out the intake or exhaust, something wrong with a valve.

It is noticeably running rough. It's fairly smooth when cold, but gets progressively rougher as it warms up.

I pulled the plug quickly during lunch in preparation for a compression test this evening and noticed that the plug is black with fuel. So I did a quick spark test and have spark.. I'm not sure what to make of this..

 

[Crackership]

I'm not sure if your year has it, but you may see if you have an igniter module. When I was dealing with my 4Runner misfire I diagnosed that module some to verify operation. Something to consider.

I'd also ohm out all your coil packs on the primary and secondary circuits.

Was this on a 3rd Gen 4Runner? I did a quick Google search and didn't find an igniter for the 3rd Gen, but maybe I'm just missing it?

 

[plcfcng]

What did the plug look like when you pulled it out ? If it looked different it can tell you alot. You can Start the engine remove radiator cap let the engine come up to temperature at idle when the engine is at operating temp look down the radiator neck see if there are any bubbles.:mullet:

 

[Bad Luck]

Was this on a 3rd Gen 4Runner? I did a quick Google search and didn't find an igniter for the 3rd Gen, but maybe I'm just missing it?

Igniter Failure?
The dtc is P1300, but I didn't have any codes with a dead miss somehow so I did the diagnostics for P1300 as wells as everything for P0300. Ended up being one of my coil packs. The secondary side was about 100 ohms higher than the other 2 coil packs, but was still well within the specifications listed in the factory service manual.

 

[LittleCaesar]

It is noticeably running rough. It's fairly smooth when cold, but gets progressively rougher as it warms up.

I pulled the plug quickly during lunch in preparation for a compression test this evening and noticed that the plug is black with fuel. So I did a quick spark test and have spark.. I'm not sure what to make of this..

Well then either it isn’t firing (ignition) or the injector is bad, even though you said you replaced them? OEM replacement?

Got a helper to crank over the engine as you test for spark?

 

[gamefreakgc]

It is noticeably running rough. It's fairly smooth when cold, but gets progressively rougher as it warms up.

I pulled the plug quickly during lunch in preparation for a compression test this evening and noticed that the plug is black with fuel. So I did a quick spark test and have spark.. I'm not sure what to make of this..

If by chance you could post a picture, that would help immensely!

 

[Crackership]

What did the plug look like when you pulled it out ? If it looked different it can tell you alot. You can Start the engine remove radiator cap let the engine come up to temperature at idle when the engine is at operating temp look down the radiator neck see if there are any bubbles.:mullet:

Plug was black with fuel, the others look fine. I've run it with the radiator cap off a couple times now, and also pressure tested it, no apparently leaks.

Well then either it isn’t firing (ignition) or the injector is bad, even though you said you replaced them? OEM replacement?

Got a helper to crank over the engine as you test for spark?

I replaced all 6 injectors with the kit from Motorwest Denso Fuel Injector Upgrade Set for 3.4L V6 4Runner Tacoma and Tundra – HP831 – MotorWest Performance They don't rebuild the OEM ones anymore, they say this is due to too high a failure rate, so they offer these Denso units as a replacement/upgrade.

I tested for spark and I have what looks like very healthy spark. Super confused.

 

[brillo_76]

If everything checks out. What happens when you swap a coil with another?

Does the misfire follow the coil?

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[Crackership]

Well, I think I figured it out. Here's the compression numbers:

1: 165
2: 30
3: 160
4: 155
5: 170
6: 160

You'll notice one of those numbers falls outside the acceptable tolerance by a little.

So, where do you all suggest sourcing an engine from?

 

[brillo_76]

Well, I think I figured it out. Here's the compression numbers:



1: 165

2: 30

3: 160

4: 155

5: 170

6: 160



You'll notice one of those numbers falls outside the acceptable tolerance by a little.



So, where do you all suggest sourcing an engine from?

Oh dear 30 is not going to fire. At least you found the cause.


If fluid levels arent dropping could be either valves or rings on that cylinder. Or a cracked head.

Engines are readily available. Just like transmissions etc.

The rest if the engine is good. I suspect head or valves not sealing.

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