Multiple misfires after rebuild ** FIXED **

If you had 1 camshaft out of time it would affect all 4 zylinders under that camshaft.

 

The kicker is that the O2 sensor with the questionable readings is the other one, not the one the OP lengthened.

 

I do vaguely recall that...
Just thinking of anything

 

When I saw that one of the wires had been lengthened I wondered if there is there any way that the wire connections for any of the O2 sensors could have gotten swapped accidentally? So bank 1 is actually connected to bank 2.

If unsure you could simply unplug one set and check the obd2 reading.

Forgive me if this seems stupid.

 

Different harness on opposite side of the motor. Plausible but not probable

 

That’s an interesting thought but I only lengthened the passenger side. The drivers side reaches down to the o2 sensor without an extension.

 

In the quoted ignition diagram - is there an intermediate connector (or splice) in the harness for the offending bank's coil pack wires? might be worth checking for breaks etc.

Additionally - I see the diagram features some in-line noise filters in the harness. Is it possible that one of those is messed up, and causing electrical interference in the circuit? I know you mentioned replacing the harness, but hey - options I guess.

Bottom line is - if the coil packs are known-good, and the spark plugs are known-good, and the injectors are good to go. Maybe another look at the wires themselves is warranted. Especially any divergence in the wire trace that can cause one bank to behave differently than the other when it comes to signaling spark.

Cheers. You need a purple heart at this point - for psychological trauma. Hang in there.

 

I have been really looking hard at the O2 sensor, but the truck misfiring without the fuel trim being leaned out made me step back yet again. Brynden29, I'm remembering you swapped injectors from 12 hole back to factory, or am I misremembering?

 

Yes, I swapped back to stock injectors from the 12 hole ones. Should I put the 12 hole ones back in?

 

Didn't the 12-holes blacken your plugs when you ran them? I seem to remember seeing pics of perfectly clean sparkplugs after you swapped to factory.

I'd say at this point, don't change things unless you are doing it to find the issue.
When the cylinders behave properly again you could throw the 12's back in. Just my 2 cents.

 

At this point, I honestly don’t remember which injectors caused the blackened plugs.

I was thinking that if the truck is running lean that putting the 12 hole injectors in could richen it up. Since the fuel trim is at -18 for bank one I would be curious if adding better flowing injectors will affect the fuel trims.

 

This data is so confusing to me.



How can the fuel rims be that far apart from one bank to the other?

 

Well, here's my logical breakdown for running rich (and causing negative trim) in general.
I got these when researching "running rich" causes a while back from the IH8MUD forum:

Dirty/broken/damaged MAF (I know you're not supposed to touch them, like, ever while cleaning - only use spray pressure from the cleaner can
Higher than normal fuel pressure
Damaged fuel pressure regulator diaphragm
Broken evap stuff
Bad O2 sensor
Coolant temp sensor (running rich if ECM things engine is still cold due to incorrect sensor reading)
Exhaust leak (before the O2)
Camshaft timing

I know you beat the timing thing to death (and many of the other issues above too), but maybe worth looking at the offending cam's sensor interface?
Maybe there's some schmoo in the hole where the cam pos. sensor goes in, causing issues?

I can't remember if you've replaced that cam sensor. If it's hard broke the truck shouldn't start at all. But if there's a signaling issue, it could cause fuel problems in one bank.

Check the signaling teeth on the crank pulley for dirt and stuff. I know if one tooth is bent even a little it can cause incorrect timing signals, and when the ECM sees a crank timing mismatch it will look to the cam sensors to identify the source, which could lead to one bank misfiring, because the ECM is trying to adjust timing for incorrect signals.

Do we know that the fuel pressure regulator for that rail is good?

 

Sounds like my prom night.

 

It's my typical solution to everything:

Burned out lightbulbs,
Squeaky chairs,
Wobbly steering wheels,
104 degree fevers,
open fractures,

"shcmoo in the hole, yep, gotta be it"

 

I appreciate all the suggestions. The odd part is that it only misfires at idle under no load. Once I put it in gear the misfires go away. Most of these issues should manifest at all times when driving. But my issue is only at idle.

 

I'm listing these symptoms as I recall them, so please change or update anything I don't have right, hoping that someone will be able to make sense of them:

Symptoms are bank 1 misfire only at idle in park or neutral even if the fuel trims are reset and zeroed out, when the engine is hot or cold; weird fuel trim numbers most likely driven by a high voltage signal from the O2 sensor; 15 inches of vacuum at idle IIRC; misfires disappear under load. ECU has been swapped, wire harness has been swapped. Like Leoshik said, maybe check the fuel pressure regulator and cam sensor on that side.

 

Yes, all correct. I replaced the fuel pressure regulator and cam sensor. I replaced them both at the beginning of all this. I pretty much have replaced all the parts. I don’t think it is a mechanical issue from a part. Base timing is perfect, I have done it 3 times. I never checked the timing marks on the cam shafts but hagrid is sure that if the cams were off a tooth then it would probably be worse and not go away like my issue does when driving.

 

Smoke test the exhaust on that bank? Maybe you have an upstream exhaust leak.

 

This one I can answer. The bank 1 fuel trim is -18 because the O2 sensor on that side is sitting at around .835 volts.

 

But why? I have tried multiple o2 sensors. Could there really be something causing it to go that rich?

 

I think at this point we may be suffering from "thread too long, can't remember what's been done w/o reading back thru 20 pages".

Hell, if it were me at this point, just for shits and giggles, I'd be tempted to go back to the OEM manifolds just to see if the condition goes away. If it does, you know it's the JBA LT's causing the prob. If not, then I'm completely and totally baffled, but wouldn't be surprised if it was something stupid (sensor, leak, etc.) between the intake manifold and air filter. Or a cracked vacuum hose. Something absolutely dumb.

 

I hear ya. The problem is, I threw away the stock manifolds. So I would have to buy a new one just to test with. I don’t really want to do that.

 

Yep, that's the question. I know it means that you're going to have to extend the wires, but I'd still swap the two sensors, reset the ECM and see where the engine re-learns the fuel trims. I honestly don't see how you can make further progress without either exonerating or condemning that bank 1 O2 sensor. The one in bank 2 is known good, so my thought is to move it over and see what it says about what's happening in bank 1.

 

Shouldn't be so hard to swap the sensors...

$20 1x Wiring Harness Extension for Toyota O2 Oxygen Sensor 36"

https://www.amazon.com/Oxygen-Senso...extension+harness+toyota+tundra,aps,66&sr=8-8

Ballenger Motorsports - 4 Way Replacement Extension for Subaru & Toyota Oxygen Sensor - 12"

https://www.amazon.com/Ballenger-Mo...extension+harness+toyota+tundra,aps,66&sr=8-1

 

I will get an extension and try it out.

 

A reading of .835 is not in and of itself necessarily a bad reading. The picture above is simply a snap shot at that moment in time. Front O2 sensors or more correctly Air/Fuel Ratio sensor will go from approximately .8 vdc(rich) to .1 vdc(lean) and resembles a sign wave as was mentioned back in July. There function is to attempt to maintain an air to fuel ratio 0f 14.1:1(stoichiometric). It's best when troubleshooting those is to have a tester that will graph the sensor.

One of the many videos Brynden has posted over time showing his front sensors are oscillating correctly at approx .8 to .1 vdc.....

Multiple misfires after rebuild

Just one of many posts where it was explained....
Multiple misfires after rebuild

 

Yep, these are all good points. The thing that I was really getting at is that the sensor is oscillating beautifully while the long term fuel trim is sitting at 18 points lean. On the other cylinder bank, completely different behavior. If the ECM is reset to back to 0, then the condition that would take the fuel trim hard lean would be a persistent high voltage reading on the O2 sensor. Maybe its a real reading caused by something else creating misfires and dumping unburned fuel into the exhaust stream. Maybe the sensor calibration is off and it's switching at the wrong condition? If I was the guy battling this problem, the sensor swap and re-zero would be my next move, just to try to shed a little more light on what might be going on.

 

IF I was the guy, I would have put the truck back the way it was born many months ago regardless if I had to get new manifolds or from junk yard. These engines are engineered to perfection IMHO. Long nor short headers nor 12 hole injectors add that much in the over all scheme of things. I would be satisfied with doing a good job of rebuilding the engine but accept the fact that the exhaust needs to be back to original. BUT, that’s just me !

 

Oh if we are piling on at this point make sure it has comprehensive and then burn it so you don’t have to mess with it anymore…. Kidding…. Not kidding.

Seriously how are you still working on this. I would have sold it a month ago just to save my sanity.