Misfires on Bank 1 only and how I fixed it

My ordeal started back on Nov 3. The last day after a weekend camping in a rural area we noticed my 2009 5.7 Tundra was misfiring and rough idling.


When I opened the trunk, I saw the conic K&N filter was loose and lying at the bottom of the box, so I reattached it correctly worried because I was driving on a short dusty road and the dust was everywhere on the engine bay, so chances were that would be the origin of the misfires.

On the highway back the trick would tremble but only after shifting and it would go away for as long as I would keep a stable speed, so I went back home an hour later without major issues.

As soon as I got home, I scanned the truck and got a P0300 (random misfires on bank 1) with misfires on Cylinders 1,5, and 7. Also a P0171 (fuel mix too lean) Next day I took it to a friend’s garage, and we swapped coils and spark plugs. One of the coils broke on the rubber, so he recommended changing the coil and installing new spark-plugs since the ones I had were the originals.

In between, I cleaned the MAF and MAP sensors, and the air filter, I also ran a can of Seafoam since it has improved the engine idle in the past.

The parts got delayed and I lost a week with the truck parked at the garage, finally next Tuesday we installed the new coil and spark plugs. To my disappointment the situation didn’t improve, so my friend recommended installing new injectors. Again, the cycle of one week waiting for the parts, installing them and getting disappointed with the results repeated. Not only did I continue having the issues, but now the misfires were on all the cylinders of bank 1 and the truck was burning gas like a dragon.


With the first days of snow arriving in Montreal and the shorter days everything became much harder. After a week of researching, we found that often general misfires on only one bank are related to timing issues.

The theory was that oil may have gotten dirty with dust and one of the hydraulic chain tensioners may have failed, so the chain on bank 1 could have jumped a tooth. That would explain why sometimes the engine would run smoothly since the VVT sprockets would be in the right position but not all the time.

The maintenance for the 5.7 Tundra doesn’t ask for a timing chain replacement before something like 300.000 miles, and my truck is 166.000 miles, but I’m not a technician (yet) and my experienced technician friend was so convinced that I decided to bite the bullet and bought the whole timing kit, including chain tensioners and water pump.


It took me a huge preparation and 2 long stressful weekends to do the job on my own, at this point I didn’t trust anyone more than I do myself (I started a 2-year technician course back in October), and I was running out of money. Additionally, I live in a small condo and the snow was already everywhere, so I had to swallow my pride and keep on working at my friend’s garage, thankful for at least having a free lift and a closed space to work on my sh*tbox on nights and weekends.


Finally on Sunday night at around 2 AM I finished reassembling everything and got the galls to run the engine again. It ran; the timing was perfect but the ‘effin misfires were still happening. I had spent around $1500 on parts and 5 long days of work just to get to the same result. I swear I wanted to burn the thing, walk away, and die frozen, except for the sense of accomplishment that doing the timing successfully on a V8 can give you, there was nothing else left on me.

At this point we are already in the middle of December, I’m morally and financially broke and a planned “vacation” with my wife and kid is coming fast. So right before leaving, I contacted a guy who’s a Toyota specialist, he does everything but mainly electric stuff at the dealership. The guy then went to the garage during the weekend while I was kidnapped away and spent an afternoon running tests using a bunch of testers and diagrams. He concluded the VTT solenoids were the reason, cleaned the things, tested the truck (just by running the engine in the parking lot I realized later), and of course, there were no misfires.


2 weeks later is January 3 and I’m coming back from vacation, so I called my friend who owns the garage to go and pick my truck. He informed me that the misfires were still there, and he was waiting for me to come back.

Go figure, at this point I’ve gone from a DIY approach to a specialist guru/final boss approach with no results in a month and a half, so I called the Toyota guy again and he explained that he thought that could happen because the old solenoids may be too old and that I should finally replace the old VVT solenoids of bank 1 for new ones.

I waited patiently for the next paycheck to arrive and bought the solenoids, went to the garage at night, removed a ton of snow from the truck, replaced the solenoids, erased the codes, and the truck ran well while parked.

As I left the parking lot to put gas, the engine light started flashing again and the misfires came back. The fact that this guy is alive, and no unexplainable disease has come to take him should be enough for everyone to be convinced that there’s no such thing as karma.

I kept on calling him for a week, after all, I paid him to fix the thing so he should at least take some responsibility and suffer with me for a while for following his less-than-excellent diagnostic.

We spent yet another afternoon chasing gremlins, now the idea was to remove the Air/fuel sensor on bank 1 from the exhaust to be sure that the catalytic converters on bank 1 were not clogged by leaving an easy way out to the exhaust through the sensor hole. With the truck up on the lift I removed the sensor, and the guy turned on the engine, looking hopeful at first and then saying that the issue was still there, so I installed the sensor back and we kept on going.

After doing a compression test (with flying colors), electronically testing the camshaft phasers, ruling out the possibility of a sheared pin on the intake phaser, and interrogating me SEVERAL TIMES about my timing chain job, the Toyota guy mentions a P0171 error, which at this point I had forgotten and thought it was a consequence of the P0300. When we checked the spark on every sparkplug of bank 1 we noticed it was very weak, so now he suspected a weak ground and left the place saying he would do more research.

That night he sent me an article about a guy having similar problems on Bank 2 on V8 a Chevy truck, and the culprit in that case was a broken grounding connection that went from the frame to the transfer case. I had seen the same article a few weeks back and I remember that around 2 years ago I noticed a broken grounding connection near my transfer case too, but it was too far back in time to be related. Since I was running out of possible reasons, I decided to buy the $12 copper braided wire.


I also found that the VVT solenoids used a $16 screen filter that goes inside the valve cover. When it clogs it starves the phasers from oil pressure, which would make total sense if the engine runs ok at certain revs but burns too much gas at higher revs, so I decided to buy the little filter too and to change the 2 things at once.


I have a 9-5 office job and the garage can’t wait for me, so another snowy week goes by. To make place for his clients my friend has now parked the truck in a different place, so I must go, pick it up, leave my car, and drive back to the garage for 3 miles at 80kph on a highway, praying for the engine to stay ok while I see the gas needle sinking fast.

Once at the garage, It took me an hour to replace the broken grounding strip, remove the valve cover on bank 1, and replace the VVT screen filter. The old filter was ok, but whatever.

Additionally, I cleaned the now blacked spark plugs on bank 1 using MAF sensor cleaner, and -just in case- installed an additional ground wire from the battery straight to the engine block on the driver side (bank 1).

Guess what? The truck ran well for like 1 mile and then started misfiring again. I scanned it again and at least the misfires were not on all Bank 1 cylinders, only 2 out of the previous 4, and the strong gas smell and white smoke made me think again of the P0171 error code.

May I have a clogged cat on bank 1 and the sucker didn’t notice? Ever since this started, I’ve never had an oxygen sensor code, yet I remember I installed a new one around 6 months ago when I removed the cats for a deep cleaning. Based on that I asked my friend for one more chance to use the lift with the intention of disconnecting the exhaust on bank 1 right from the upstream cat.


Another week passed by. It's the end of January and the freezing temperatures and snow all around have pushed me to slow down on the things I cannot control and rather focus on planning. I’ve been advancing on my mechanic technician course, asking teachers about possible causes, and “temporarily” driving a 2003 4.7 4Runner that we bought to flip and sell but got dented when it was ready to be sold back in December. (When the poor does the laundry it pours)

2 years ago I bought the Tundra because I needed something big enough to move a recently acquired camper trailer, but with one kid already out of home and the other one in college, we would benefit more from downsizing, so the trailer goes, the Tundra too and I will probably keep the 4Runner that I fixed and know well, and acquire a smaller camper trailer for us.

During the week I kept turning the internet upside down every night until midnight, trying to find that small clue that could shed light on my almost exhausted research. I went to my Amazon account and checked all the parts bought during the last year, I opened the error code reports stored on my phone, and even checked some photos from every repair I’ve done in the last year, then created a timeline of events.

I cleaned the cats on May 18, replaced one O2 upstream sensor on June 9, replaced the MAF on July 15, got back the cat P0420/0430 on October 19, and had the misfires on November 3… May it be related to the O2 sensor? It was upstream but I don’t recall if it was on bank 1 or bank 2, besides, it was more than 6 months ago and I have no errors related to that other than the P0171 which could be an issue with the wiring from the sensors, or even the ECU, because is the only thing in charge of the fuel missing that I have not checked yet. I got the chills.

As planned, I went one more time to the garage to disconnect the upstream cat on bank 1, but my friend suggested trying first and disconnecting just the 02 sensor (AKA Air/Fuel sensor) from its harness without removing it from the exhaust, before attempting to remove the exhaust, so I did it and took the truck out, this time without even cleaning the spark plugs and while polluting everything with white smoke.

1 mile, 2 miles, 3 miles, no engine light, the exhaust stops smelling and the smoke is no longer white, the problem was gone, I couldn’t believe the problem was finally gone, I was cautiously smiling in relief, I couldn't afford to smile big because I wasn't sure I still had anything left in me to face another disappointment, yet, I was probably the happiest person on the highway that day.

When I took out the upstream sensor on bank 1, I found that it was the one I bought from Amazon (Dr. Cax) back in May, we tested it and the b*stard showed resistance values well within the acceptable range, but there were no doubt it was to blame for all the ordeal I had gone through in the last 3 months. 3 days later I installed a good OEM (NGK) from Parts Avatar (Canadian vendor) cleaned the codes and the truck has been running fine ever since.

Things I learned:

• To be thankful for the help received but never take a recommendation blindly even if it comes from the guy “who knows too much” People have good intentions but it’s your skin in the game, not theirs.
• Some technicians can have a PhD, but it doesn’t mean they are good at what they do. It’s just water under the bridge.
• If you don't test-drive you are doing a half-assed job.
• I can now successfully do a timing chain service on a 5.7 V8. And I know this engine and truck from the inside out. That monster is slain.
• The hardest part while diagnosing a problem is to untangle the mix of codes and finding which code points to the causes and which ones are just a collateral effect.
• Conic K&N filters are BS (mine came with the truck). They look cool, but the gain in power or efficiency is not significant enough to justify replacing the perfectly fine OEM.
• Avoid buying unknown brands, in fact, I’ll reinstall the old fuel injectors (after cleaning them) and VVT solenoids soon. I know it is super tough in times like these, but if you have no other option maybe you should re-evaluate your vehicle choice.
• Keep your head above the water, as long as you are breathing you are in the game, and it’s a resistance game, not a speed one.

Thanks for reading.

 

Good stick-to-it-ness. This issue would have been quite frustrating. Nice work on that timing chain change.

Another thing to add to your learned list: Don't buy critical automotive parts from Amazon. Just don't do it.

Buy once and pay slightly more from a reputable place, cry once and not continually!!