Ok--School me on Misfires

sweet88gt

sweet88gt

New member
Backstory is here but warning long read
https://www.toyota-4runner.org/3rd-gen-t4rs/283856-lets-talk-tests.html?highlight=sweet88gt

What are the causes of misfires? Lets go back to basics here.

Talk to me like I have no knowledge and school me on the causes of misfires in the 3.4 V6.

At present time I have pending codes for misfires 1-2-3-5-6 Once I see these it will throw the CEL and die.
Many of the normal items replaced like spark plugs--wires--new coils--Motorwest Fuel injectors--fuel filter--fuel pressure regulator--fuel pressure 42 psi--good compression--replaced a few bad vac lines

So Im not seeing any coolant loss. I have not done a leak down test.

All I want is this thing to get fixed and I will make it a woods truck.
 
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You need:
1)Good compression
2)Correct amount of fuel
3)Spark strong enough to ignite (and at the correct time)
4)Correct component timing
 
Bad Luck said:
You need:
1)Good compression
2)Correct amount of fuel
3)Spark strong enough to ignite (and at the correct time)
4)Correct component timing
Click to expand...

Seems simple enough!!!
I have been chasing this for 3 months on and off. We I get time I tinker with it.

Off the wall thoughts could be bad gas, or failing fuel pump. Im at a 1/4 tank (after those 3 months) and might be ready to drop the tank and inspect.
 
sweet88gt said:
Seems simple enough!!!
I have been chasing this for 3 months on and off. We I get time I tinker with it.

Off the wall thoughts could be bad gas, or failing fuel pump. Im at a 1/4 tank (after those 3 months) and might be ready to drop the tank and inspect.
Click to expand...
Bad gas is a possibility. 42 psi doesn't sound like a bad fuel pump to me though. What were your compression numbers? Dry or wet?
 
Was this issue happening before you replaced all those parts? If not when did it start, and where were the parts sourced from? If you had a bad coil pack before and replaced them with something like a counterfeit eBay part being sold as genuine oem it could cause issues.
 
RandyBobandy said:
Was this issue happening before you replaced all those parts? If not when did it start, and where were the parts sourced from? If you had a bad coil pack before and replaced them with something like a counterfeit eBay part being sold as genuine oem it could cause issues.
Click to expand...

Truck drove great for a yr then one day it stalled. Since then I have sourced info and tracked down dead end leads.

That thread above is very long but it lays out what I did step by step.

I sourced most of those parts via Toyota dealerships online and I used Yotaparts as well. I skipped Amazon.
 
Bad Luck said:
Bad gas is a possibility. 42 psi doesn't sound like a bad fuel pump to me though. What were your compression numbers? Dry or wet?
Click to expand...

I followed the same details from Tim the guy on Youtube.

I would have to find the numbers for accurate but I seem to remember 190-200 if I recall.
 
I don’t like your 12.9v at idle with nothing on.

Something isn’t right.

Grounds, bad Alt, bulb in dash for charging.........


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19963.4lsr5 said:
I think he should fix the voltage first. I think he is trying but can’t get the plug out of the back.


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Click to expand...

Agreed. There's something about the low voltage that was causing mine to throw misfire codes even though it didn't appear to be misfiring. It did stall out a couple of times on me during the period I was trying to diagnose it. Mine was charging (barely) at higher RPM but only getting around 12.5 at idle.
 
sweet88gt said:
I could only hope it was that easy. Fingers crossed
Click to expand...

I hope it's that easy for you too! Took me a couple of months to figure it out and it all culminated in me hearing a funny noise while I was way off in the bush in algonquin park. I cut that tour short and then I had to make the call to try and get a new alternator at the closest parts place (meaning wait until monday and then drive an hour to get there) or try and drive home (4 hours) and hope for the best. I went with the drive home option but then it started raining, so I had to run wipers and lights a good part of the way home to make it more fun. I made it though!
 
So still seeking help

Im waiting on parts for alternator.
Picked up from the junkyard this morning an ignitor. Replaced while checking the output of said alternator at 13.9 volts cold the truck shut off again. Was at idle and coolant temp was around 150 so it had not even gotten warmed up yet. Again no start with misfires on 3 cylinders.

So while I was at the junkyard (Im desperate) I picked up what looks to be like an ok alternator--dirty and grease cover on outside. I picked up an ECU from a 97. And the above ignitor.

The donor vehicle was manufactured 6 of 97
Mine is a 10 of 96 but titled as a 97.

Are these differences going to matter ??
 
Without me losing my mind, things I have not checked.

Timing
Can somehow the timing be off ?
Crank sensor
How can I test this part?
Bad gas
I can't even get it to the gas station but could get 5 gallon can I suppose. Its now on 1/4 tank

Maybe a match down that damn tank would fix my issues.
 
19963.4lsr5 said:
I don’t like your 12.9v at idle with nothing on.

Something isn’t right.

Grounds, bad Alt, bulb in dash for charging.........


Sent from my iPhone using Tapatalk
Click to expand...

With a/c on high headlights on cold 14.34
Ran for 20 minutes same load 13.43

Junkyard I think OEM can't be sure alternator.
Reman was in there I didn't notice until after I got it out.

No codes yet
 
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