Misfires on one bank, one bank only. . . FIXED!!!! (1 Viewer)

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Joined
Dec 1, 2018
Threads
4
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72
Location
Nebraska, wish I was back in South Dakota
Done some searching on the forums, and haven't seen one QUITE like this yet.

History: '99 LX, 231,000 miles, CA car originally, I bought it from the Dallas, TX area and brought it back to the nord-land. T-belt done about 30-40k miles ago with the Aisin kit, recently (within the past 30 days) replaced alternator with Aisin rebuild, various steering bits and bobs and fuel filter (Toyota) replaced recently as well. Rough idle problem predates alternator replacement. When I replaced the alternator I drained the coolant and pulled the lower radiator hose, and refilled the coolant with a vacuum system, and checked it for a couple of days. Saw no drop in coolant at either the radiator or the overflow tank.

Symptoms: Originally the rough idle would manifest itself after a long(ish) drive on the highway. Don't know if long drive in town would cause it or not. Rough idle would seem to come close to stall, but wouldn't get there completely. If I'd put it in P or N and give it a quick rev, the idle would smooth out. No CE lights during that period. Then two days ago the rough idle seemed to be worse, and seemed to manifest itself while sitting in my driveway while warming up in the AM before my 45min highway commute. Got to work, and didn't seem to have a problem. Go home and before I get to the highway, it has rough idle at stoplights. I gave it the quick rev in P or N, and it'd smooth out until I put it back into D. Rough Idle would come back when back into D. Still no CE light. At one stoplight I left it in D, stomped on the brake pedal with one foot and revved the engine with the other foot. THAT caused a CE light!! In fact, I got a FLASHING CE light for a couple seconds. The light then went solid. I didn't have my computer with me, and the vehicle wasn't running any worse, so I drove it home. Put my computer on it at home and had ELEVEN codes. They were Bank 2 pre-cat O2 sensor, and 2 each of the following: Random Misfire, and each even numbered cylinder misfire.

My first thought is vacuum lines, but I'm having trouble linking that to misfires on only one side of the engine. Fuel delivery has also run across my mind, but again I have trouble linking that to misfires on only one side of the engine.

Anyone have ANY thoughts?? Where should I begin my search??

Thanks in advance!!
 
Maybe your timing belt jumped and your timing is off. There's a small cover that doesn't get put back sometimes after a timing belt change an a rodent might get in there and cause the belt to jump.
 
Sounds like timing is off or head gasket took a dump, both of which are possibilities given the recent work done.
 
Compression and leak down test time.
 
maybe check with the head gasket leaking? It is simple diy and won't cost much. just saw this video yesterday which may help.

Good video! I really hope that's not the issue. . ..
 
Sounds like timing is off or head gasket took a dump, both of which are possibilities given the recent work done.
Not sure how timing could get off based on alternator and fuel filter? Timing belt was 30-40k, and several years ago. I'm open to further thoughts on this.

Thanks!
 
Maybe your timing belt jumped and your timing is off. There's a small cover that doesn't get put back sometimes after a timing belt change an a rodent might get in there and cause the belt to jump.
I did the work and made DARN sure that little rodent hole triangle was back in there. Still worth the check though. Thanks.
 
I agree head gasket "usually" 2 cylinders next to each other. But don't rule it out, until compression test. But even if all cylinder have little to no compression on BK2, it does not mean head gasket for sure bad. If head gasket that bad, than head is likely badly wrapped. You'd see coolant along head gasket seams. You'd likely see coolant in oil (milkshake)

BK2 dead I repaired once. Was cam sprocket spun on cam, cutting away knock pin. From all accounts of owner. It ran rougher and rougher after each start, then wouldn't start at all. It was just after someone else did a T-belt job. That someone didn't use a torque wrench. Cam bolt was loose. Seem each start cam moved more and more off the mark.

You could also have a wire of electronic issue. Like rodents eating away at wiring, or water entry into cabin.

I'd first visually inspect head gasket, coolant level, oil, wiring in and around engine bay & O2'. Than do a compression test followed by leak down in bad (wet optional before leak dn, to help isolate).


 
I agree head gasket "usually" 2 cylinders next to each other. But don't rule it out, until compression test. But even if all cylinder have little to no compression on BK2, it does not mean head gasket for sure bad. If head gasket that bad, than head is likely badly wrapped. You'd see coolant along head gasket seams. You'd likely see coolant in oil (milkshake)

BK2 dead I repaired once. Was cam sprocket spun on cam, cutting away knock pin. From all accounts of owner. It ran rougher and rougher after each start, then wouldn't start at all. It was just after someone else did a T-belt job. That someone didn't use a torque wrench. Cam bolt was loose. Seem each start cam moved more and more off the mark.

You could also have a wire of electronic issue. Like rodents eating away at wiring, or water entry into cabin.

I'd first visually inspect head gasket, coolant level, oil, wiring in and around engine bay & O2'. Than do a compression test followed by leak down in bad (wet optional before leak dn, to help isolate).


Thanks.

Checked the oil and NO milkshake. Coolant level is correct in both rad and overflow tank. I haven't crawled under it yet, but no obvious external signs of head gasket failure. When I did T-belt, I didn't mess with the cam sprockets because I didn't have leaking seals there, so hopefully that's not the issue. I'm going to do an exhaust gas test this evening after I secure the kit from O'Reilly's (closest store with a tool rental program). I'll definitely do a compression test this weekend. I'll continue looking around for an electrical issue before I get to that though. Haven't seen any rodents around, but that's a possibility in rural Nebraska.
 
Did the chemical test in the video posted above to determine if there are exhaust gases in the coolant, and the solution did NOT change color. Did it twice, same result both times. I guess that mostly rules out head gasket, and means I continue looking at wiring and do compression tests.
 
I agree head gasket "usually" 2 cylinders next to each other. But don't rule it out, until compression test. But even if all cylinder have little to no compression on BK2, it does not mean head gasket for sure bad. If head gasket that bad, than head is likely badly wrapped. You'd see coolant along head gasket seams. You'd likely see coolant in oil (milkshake)

BK2 dead I repaired once. Was cam sprocket spun on cam, cutting away knock pin. From all accounts of owner. It ran rougher and rougher after each start, then wouldn't start at all. It was just after someone else did a T-belt job. That someone didn't use a torque wrench. Cam bolt was loose. Seem each start cam moved more and more off the mark.

You could also have a wire of electronic issue. Like rodents eating away at wiring, or water entry into cabin.

I'd first visually inspect head gasket, coolant level, oil, wiring in and around engine bay & O2'. Than do a compression test followed by leak down in bad (wet optional before leak dn, to help isolate).


Is there a possibility that a bad O2 sensor on that bank could cause the misfires? Or a bad cat?
 
I don't think so. It would be a reach to have: Fuel trims so rich on BK2, it fouls every spark plug to point they don't spark. Or so lean, they burn up the plugs. In either case you should have had, O2 codes at very beginning of rough idle.

But 100% sure, misfire can cause a O2 code.
 
I don't think so. It would be a reach to have: Fuel trims so rich on BK2, it fouls every spark plug to point they don't spark. Or so lean, they burn up the plugs. In either case you should have had, O2 codes at very beginning of rough idle.

But 100% sure, misfire can cause a O2 code.
Thanks, I appreciate that, but I'm seeing some other information that suggests this COULD happen and realized that I may have left out some data that I didn't realize was crucial.

I did mention that I had upstream O2 sensor code for that bank, but forgot to mention that I had that code several weeks before this. I thought that was related to the bad alternator as they both happened about the same time and the O2 code cleared up in the week between the alternator being replaced and this issue cropping up hardcore. Another thing is that the intermittent, somewhat rough idle I mentioned has been going on for several months now, but only after a long drive. I thought that was fuel related and why I replaced the fuel filter. Didn't know if that was connected to this more hardcore condition or not. Now I'm questioning that with an O2 code and seeing these videos. Take a look and let me know what you think:





Bank 2 Misfire case study: Chevy Avalanche - Part 2 - https://www.youtube.com/watch?v=Vv79lQ64DGA

Yeah, I know they're not a Hundy, but the problems are SOO similar to what I'm having, I think it's worth a shot. This weekend I'll pull the right bank plugs and see what they look like, and might try to unplug that side's upstream sensor and see what it drives like. I THINK my code reader will show me fuel trims and O2 performance, so I'll check that too. Plugs probably have 30-40k on them, and I used the proper Denso or NGK (I can't remember) plugs when I replaced them. So they should have some (natural) life left.

All options on the table still, but seeing these videos is seriously leading me in this direction as a next step.

I did also continue looking for bad vacuum lines or bad wiring last night, and didn't come up with anything, but have a lot more to look at in that area as I've not crawled under it to look down there yet.

Keep the ideas coming!!
 
"I did mention that I had upstream O2 sensor code for that bank, but forgot to mention that I had that code several weeks before this"

Seems to be a lot of "forgetting to mention" lately in mud.

For sure swap, or just buy an new Denso O2 and pop in in.
 
"I did mention that I had upstream O2 sensor code for that bank, but forgot to mention that I had that code several weeks before this"

Seems to be a lot of "forgetting to mention" lately in mud.

For sure swap, or just buy an new Denso O2 and pop in in.
Sorry about that. Totally my fault.

Thanks for the help! I’ll keep folks updated.
 
Sorry that I've not posted an update for a while. Turns out the Oxygen sensors were indeed the problem. Computer showed that both front sensors were tired, and fuel trims were out of whack. Bank 2 (right, or passenger side) was definitely worse. Got new Denso's from RockAuto. Here's what I pulled out of Bank 1:

Bank 1 sensor 2.jpg


Looked just like the new Densos I had!! Good!

Here's Bank 2:
Bank 2 sensor 1.jpg


Uhhhhhhhh. . ..

Yeah, so long story short, the new CORRECT ones are in, and several hundred mile later the issue hasn't cropped back up yet.

I'm not sure if they put in a downstream sensor, or a different manufacturer, but that's not what the Denso sensor looked like.

Thanks for everyone's help!!!
 

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