Misfires on 3 cylinders—likely evap issues, flooded charcoal canister led to misfires (2021, 75K miles)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

HSTexan said:
Well it was hopeful for a second—they called a few hours ago and said they did the plugs and EFI and drove it and it drove fine. Then let it cool completely and drove it again and everything was still fine. Said they checked the fuel trims too and everything seemed normal still.

Wife and I went over to pick it up hopeful, but still cautious. Made it about 2 miles down the road and the dash lit up like a Christmas tree again. Didn’t bother pulling the codes, just limped it back to the dealership again. It’s close to EOD so they said they’d start digging into it again tomorrow morning

Also attaching a photo of what the first tech considered serious scoring (bottom right)—sent it to a buddy who is actually a Toyota master tech up in Ohio and he was under the impression it looked fairly minimal.

View attachment 4117334
Click to expand...

Sorry man. I mean at least it still might not be a HG issue or something catastrophic? Don’t lose hope just yet.

I had the EFI service done recently and yeah it’s a big nothing. Basically clean the throttle body and some fuel additives. Don’t think that’s gonna fix anything that’s actually wrong with the vehicle.
 
Still hopeful it’s nots a HG. Hopefully they get some clearer direction tomorrow.
 
Mingus Dew said:
Sorry man. I mean at least it still might not be a HG issue or something catastrophic? Don’t lose hope just yet.

I had the EFI service done recently and yeah it’s a big nothing. Basically clean the throttle body and some fuel additives. Don’t think that’s gonna fix anything that’s actually wrong with the vehicle.
Click to expand...
Yeah I mainly did the EFI so that if this went further and required a case with Toyota corporate I don't have anything on record of denying recommended services. If anything was going to fix it from what they did, it would have been the plugs.

Zill said:
Have they drained the tank? I’m wondering if it’s just bad gas.
Click to expand...
They didn't; I actually asked about it specifically as well. They hadn't checked it since it was limited to one bank and none of the codes were lean codes either. I'll likely revisit it and ask they pull some fuel and check it. Would be great if it was that simple--I had just filled up Friday evening before having the issues Saturday morning. 36 gallons worth between the main and LRA so if it's fuel there was plenty of it to cause a problem--I'd much rather toss that than anything else at this point

I'm for sure leaning away from head gasket now after the leak down held solid over the weekend.
 
Bloc, didn’t your head gasket issue result in a pool of coolant getting in the combustion chamber after letting it sit for a bit? If there’s no coolant in the combustion chamber, no exhaust gas in the coolant, and the coolant level is okay, then I really doubt it’s a head gasket issue.

It could be bad gas with a ton of water in it, and the car does not like it and is sucking up the water that’s separated in the tank once you get the car moving and gas sloshing around (gas and water do not mix). With all the oil issues across the globe and higher ethanol content, maybe bad batches are getting produced?

Or it could be a bad fuel injector, which can make all the cylinders on that one bank get thrown out of whack (that’s highly unlikely though).

Another item could be a bad wire such as a rodent chewing on it, that’s barely hanging on.

Lastly, have they checked the 02 sensors on that side of the engine? That could mess with the fuel trims and make it run lean and cause the plugs to be so dry.
 
Last edited:
aztoytec said:
Do you know what the fuel trim was when it threw the codes? They should be able to see it.
Click to expand...
I do not, they said the fuel trims looked good after the fact—that was the only reason why bad gas gives a bit of pause. They should have seen it overcompensating for lean A/F if there was water contaminating the mixture
 
Zill said:
Bloc, didn’t your head gasket issue result in a pool of coolant getting in the combustion chamber after letting it sit for a bit? If there’s no coolant in the combustion chamber, no exhaust gas in the coolant, and the coolant level is okay, then I really doubt it’s a head gasket issue.

It could be bad gas with a ton of water in it, and the car does not like it and is sucking up the water that’s separated in the tank once you get the car moving and gas sloshing around (gas and water do not mix). With all the oil issues across the globe and higher ethanol content, maybe bad batches are getting produced?

Or it could be a bad fuel injector, which can make all the cylinders on that one bank get thrown out of whack (that’s highly unlikely though).

Another item could be a bad wire such as a rodent chewing on it, that’s barely hanging on.

Lastly, have they checked the 02 sensors on that side of the engine? That could mess with the fuel trims and make it run lean and cause the plugs to be so dry.
Click to expand...
Rodent damage was a possible thought Saturday when I was riding two hours back in the tow truck. Would be awful to track down, but minimally invasive. I’m not 100% sure about the O2; I’d imagine they have their list of items they ran down and when it looked like things improved they stopped.
 
HSTexan said:
Rodent damage was a possible thought Saturday when I was riding two hours back in the tow truck. Would be awful to track down, but minimally invasive. I’m not 100% sure about the O2; I’d imagine they have their list of items they ran down and when it looked like things improved they stopped.
Click to expand...
Hmm, but that wouldn’t explain the breakdown in the first place.
 
HSTexan said:
Rodent damage was a possible thought Saturday when I was riding two hours back in the tow truck. Would be awful to track down, but minimally invasive. I’m not 100% sure about the O2; I’d imagine they have their list of items they ran down and when it looked like things improved they stopped.
Click to expand...
I’d stick a flexible borescope camera under the intake manifold (into the valley plate area) and check for signs of a rodent. Takes less than a minute.

But it sounds like you need one of their best techs to do some serious troubleshooting work. Best of luck
 
Yes I had pink coolant pooled in the CC after letting it sit overnight, which is a very typical blown head gasket symptom.

If you had a rodent chewing issue I wouldn’t expect it to be under the manifold. The only wires down there are for the knock sensors which have specific codes associated with them, or SAIS valves. I haven’t looked closely at the wiring diagrams but a shared ground in the coil harness on the passenger side could lead to these symptoms, in theory.. but that wire would probably be high on the rear of the engine in the huge harness bundle, or maybe on the ground attachment to the rear of that cam tower against the firewall.
 
I meant to look for a nest under the manifold. You’re right, the only wires under there (based on my limited knowledge) are knock sensors which would throw a different code. Definitely a long shot
 
I only skimmed over your thread so far, so it may have been covered. This is a very different Toyota (a friend's Avalon V6 around 2015ish) but was a situation I have not seen before. The engine had multiple, random misfires that would come and go, much like you are having. The dealer wanted to replace all coil packs at a pretty hefty price. I had a mechanic friend of mine look at it and he discovered it had a lone coil pack that was bad, but would ground other random coil packs out through the wiring intended for full engine shutdown- either security system trigger, or sudden crash impact trigger. That made it seem like there was a larger problem. A couple hundred bucks into one new Denso coil pack and all fixed.

Again, a very different engine and year, but still Toyota engineering. Just something to think on.

Good luck!
 
With the year and mileage I would really be surprised to see a head gasket failure.

Could be rodent damage. Check the wiring from the coils and trace the harness back to the ECM. Chewing should be very noticeable. BUT—if there are only misfire codes for those cylinders then the damage would probably be very close to the coils since that wiring becomes bundled with more and more unrelated systems the closer you get to the ECM.

With the info here I’d first look at a fuel quality or fuel delivery problem.

Edit: just saw the cylinder photo, looks normal. BUT those plugs look terrible. Is there diesel in the gas…? Our Sam’s Club gas station had diesel delivered in the unleaded tank 2 years ago, it was a disaster.
 
Last edited:
dogfishlake said:
I only skimmed over your thread so far, so it may have been covered. This is a very different Toyota (a friend's Avalon V6 around 2015ish) but was a situation I have not seen before. The engine had multiple, random misfires that would come and go, much like you are having. The dealer wanted to replace all coil packs at a pretty hefty price. I had a mechanic friend of mine look at it and he discovered it had a lone coil pack that was bad, but would ground other random coil packs out through the wiring intended for full engine shutdown- either security system trigger, or sudden crash impact trigger. That made it seem like there was a larger problem. A couple hundred bucks into one new Denso coil pack and all fixed.

Again, a very different engine and year, but still Toyota engineering. Just something to think on.

Good luck!
Click to expand...
Different make but something similar happens when the coil packs go bad on the Porsches. The dash lights up like a christmas tree with all sorts of warnings.
here's a recent example: Ignition Coil Failure and Loss of Cylinder #6 - Rennlist - Porsche Discussion Forums - https://rennlist.com/forums/981-forum/1467446-ignition-coil-failure-and-loss-of-cylinder-6-a.html
 
GrouchyTech said:
With the year and mileage I would really be surprised to see a head gasket failure.

Could be rodent damage. Check the wiring from the coils and trace the harness back to the ECM. Chewing should be very noticeable. BUT—if there are only misfire codes for those cylinders then the damage would probably be very close to the coils since that wiring becomes bundled with more and more unrelated systems the closer you get to the ECM.

With the info here I’d first look at a fuel quality or fuel delivery problem.

Edit: just saw the cylinder photo, looks normal. BUT those plugs look terrible. Is there diesel in the gas…? Our Sam’s Club gas station had diesel delivered in the unleaded tank 2 years ago, it was a disaster.
Click to expand...

I have not heard of any other reported cases of gas issues yet locally, it's a very popular 7/11 down the street, but it does seem like a good starting point for them to check now. I do feel like I'm playing a bad game of telephone between what the shop foreman is telling my service guy and what my service guy can tell me. I had asked if they compared those two plugs against the other 6 and couldn't get a solid answer. I know they tested the coil packs, but I'm not sure if they only tested the bad cylinders or all 8. Now that this isn't as easy as they thought I'm going to have to press them to take more detailed notes to give me updates.

I think everyone has moved past the head gasket thing; probably should update the thread title to take that out. Between leak down holding and no visible signs of coolant let alone the age and mileage, it seems like it would be extremely unlikely.
 
There's been a few low(ish) mileage 200s with blown head gaskets reported here. Older model years though.

It sounds to me like what they did was a coolant system pressure test - not a per-cylinder leakdown test.
 
rexington14 said:
There's been a few low(ish) mileage 200s with blown head gaskets reported here. Older model years though.

It sounds to me like what they did was a coolant system pressure test - not a per-cylinder leakdown test.
Click to expand...

After I talked to my tech buddy and he raised the same question I specifically ask if it was a cylinder leak down or the coolant system pressure test and he did say it was cylinder leak down.
 
HSTexan said:
After I talked to my tech buddy and he raised the same question I specifically ask if it was a cylinder leak down or the coolant system pressure test and he did say it was cylinder leak down.
Click to expand...
There’s just no way the cylinder leak down is holding pressure overnight.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom