Ecu misfire?

[TTO5]

Here's the number 4 piston after the 2nd and 3rd treatment of seafoam top engine cleaner injected via a vacuum hose. It's getting rid of a lot of carbon. Too early to say for sure if this is fixing my issue. If anyone knows what this weird discoloration on the number 4 cylinder is I'd like to hear it. It was more pronounced in the 2nd cleaning result pic vs the 3rd cleaning.

 

[NikP]

Interesting discoloration. Is this unique to the misfiring cylinders only? If so, it might be a clue.

 

[TTO5]

Interesting discoloration. Is this unique to the misfiring cylinders only? If so, it might be a clue.

I didn't look in the other cylinders for it but I'm pretty sure it's only in cylinder 4. My feeling is some carbon was stuck to a piston ring maybe and caused this mark,?

 

[TeCKis300]

Just wanted to ad that this replacement engine had a lot of carbon buildup I'm assuming from many short trips. It had only 45k miles and came out of a 2011 lx570. Might these carbon deposits be causing misfires?

Carbon buildup can definitely cause misfires as it increases compression and creates hot spots. Though it'll usually be a symptom more so in a high load situation and you're getting it when the engine is unloaded at operating temp? Either way, the carbon buildup is only symptom of the misfire that you already know is happening. If it was a root cause, it should have lessoned after cleaning.

Sorry you're going through this.

Looking at the firing order 1-8-4-3-6-5-7-2, what is odd is that 4 and 7 are third in sequence. These vehicles are so integrated without a separate ignitor from the ECU. I believe you have already swapped coils around?

Do you have the Ignition noise filters in place on the heads? I doubt that could cause this misfire as I believe it's just to attenuate electrical noise.

Hard to see a pattern in the wiring that ties 4 and 7 together.

I'm not sure what discoloration you're referring to. Just taking a guess out of left field but I wonder if this engine has been overheated or seen severe detonation before.

 

[TTO5]

Carbon buildup can definitely cause misfires as it increases compression and creates hot spots. Though it'll usually be a symptom more so in a high load situation and you're getting it when the engine is unloaded at operating temp? Either way, the carbon buildup is only symptom of the misfire that you already know is happening. If it was a root cause, it should have lessoned after cleaning.

Sorry you're going through this.

Looking at the firing order 1-8-4-3-6-5-7-2, what is odd is that 4 and 7 are third in sequence. These vehicles are so integrated without a separate ignitor from the ECU. I believe you have already swapped coils around?

Do you have the Ignition noise filters in place on the heads? I doubt that could cause this misfire as I believe it's just to attenuate electrical noise.

Hard to see a pattern in the wiring that ties 4 and 7 together.

View attachment 3783860

I'm not sure what discoloration you're referring to. Just taking a guess out of left field but I wonder if this engine has been overheated or seen severe detonation before.

Hi and thank you for the info. Yes I would say so far I am seeing less frequency of the mil after the decarbonize. Today I drove 20 miles then let it idle for 15 min and it didn't trigger the mil. I will try and drive it over the next several days to see if it disappears. I am running bg 44k in the gas tank for now. Yes coils were moved with no change. Not sure about the filters but my original harness was used. Not sure about the overheating but I didn't see any mention in the donor engines service history. I'll update as I go. Thanks again

 

[TTO5]

So far so good. Drove it to work today. Idled in parking lot for about 15 min. Usually long enough to trip the mil. At the end of the day I started it and let it run 15 to 20 min. No mil. Drove home 20 miles Idled in driveway no mil. I don't want to get my hopes up too much but so far this decarbonize had made the most impact on the situation. I'll report again towards the end of the week . Thanks for everyone's support and help.

 

[TeCKis300]

So far so good. Drove it to work today. Idled in parking lot for about 15 min. Usually long enough to trip the mil. At the end of the day I started it and let it run 15 to 20 min. No mil. Drove home 20 miles Idled in driveway no mil. I don't want to get my hopes up too much but so far this decarbonize had made the most impact on the situation. I'll report again towards the end of the week . Thanks for everyone's support and help.

That's promising!! Give her a good ole Italian tune-up with some RPM and load.

Still curious how this happened. Wonder if the doner it came out of only did short trips rarely getting to operational temp? Or not using the right octane for heavy use. Or...

Kudos for the patience and perseverance.

 

[bloc]

Second on Italian tuneup.

Glad this is headed in the right direction.

 

[TTO5]

Well it was good for a couple days. Drove it earlier tonight allowed it to idle for 15 min after driving mixed highway and local. Everything fine. Cooled off for a few hours. Drove it about 10 miles pulled over Idled and within a few minutes mil flashing with 304 307 again. Turned truck off, restarted it this time light on solid no misfire protection mode. Turned off ignition . Let sit 5 min. Restart , no mil at all, drive 10 miles home with 5 min idle at home, no mil. My assumption is there's still a ways to go in cleaning this carbon out. Hoping I'm on the right track. Getting tiring.

 

[TeCKis300]

Well it was good for a couple days. Drove it earlier tonight allowed it to idle for 15 min after driving mixed highway and local. Everything fine. Cooled off for a few hours. Drove it about 10 miles pulled over Idled and within a few minutes mil flashing with 304 307 again. Turned truck off, restarted it this time light on solid no misfire protection mode. Turned off ignition . Let sit 5 min. Restart , no mil at all, drive 10 miles home with 5 min idle at home, no mil. My assumption is there's still a ways to go in cleaning this carbon out. Hoping I'm on the right track. Getting tiring.

If you have access to higher octane fuel, or octane booster additive, give that a whirl to stave off the detonation. That might allow you to add some fuel injector cleaner or seafoam to the fuel and run a tank through.

 

[TTO5]

If you have access to higher octane fuel, or octane booster additive, give that a whirl to stave off the detonation. That might allow you to add some fuel injector cleaner or seafoam to the fuel and run a tank through.

I'm just concerned why it's always those 2 cylinders.

 

[TeCKis300]

I'm just concerned why it's always those 2 cylinders.

Agreed

 

[rexington14]

Because the HG may be blown there? Do a compression test of those 2 cylinders on a cold engine in the morning. Then drive it till it gets hot and you get the misfires. Shut down and immediately pull the plugs for those 2 cylinders and retest the compression.

 

[TeCKis300]

Remind me if you've checked fuel pressure? Sure, it will generally affect all cylinders but who knows.

The difference between cold and hot operation, also known as open loop and closed loop is fueling richness. Cold operation will inject more fuel. In closed loop operation, fueling will be at a more stoichiometric ratio.

I don't think it's hot enough at idle to cause pre-ignition. Raher the misfire is probably a result of insufficient atomization or fuel availability to light off. Fuel trapped in carbon, HG leak, timing....fuel/air/spark???

 

[AcmeSys]

Engine ground cables measure good? Any pushed/bent pins in the coil connector or loose sockets? Did you replace the knock sensors or their harness? Is a "missfire" code indicative of knocking or loss of spark?

 

[TTO5]

Remind me if you've checked fuel pressure? Sure, it will generally affect all cylinders but who knows.

The difference between cold and hot operation, also known as open loop and closed loop is fueling richness. Cold operation will inject more fuel. In closed loop operation, fueling will be at a more stoichiometric ratio.

I don't think it's hot enough at idle to cause pre-ignition. Raher the misfire is probably a result of insufficient atomization or fuel availability to light off. Fuel trapped in carbon, HG leak, timing....fuel/air/spark???

Hi fuel pressure is good. Drove 100 miles today with some idling. Mil never came on

 

[TTO5]

Engine ground cables measure good? Any pushed/bent pins in the coil connector or loose sockets? Did you replace the knock sensors or their harness? Is a "missfire" code indicative of knocking or loss of spark?

Hi. No didn't replace knock sensors. Grounds were checked. No loss of spark.

 

[TTO5]

Came on twice tonight and went into misfire protection mode. I'm at a loss here. I measured warmed up compression in 4 and 7 as well as 2 others and they all read 165 psi

 

[AcmeSys]

Hi. No didn't replace knock sensors. Grounds were checked. No loss of spark.

Grounds were checked how? Coil harness pins and sockets are good? In diagnosing intermittent bugs I wouldn't trust any prior work that may have occurred unless you did it yourself.

Any sign of oil in the plug tubes? Spray out the coil sockets with contact cleaner?
Have you tossed in new plugs in the problem jugs? (crapped out or cracked plugs fresh from the box is a thing)
Plug gaps out of whack?
Bad Cam/Crank position sensor?
Pull the engine covers and start hosing down the top end with contact cleaner and listen for a idle shift from sucking it into a vac leak?
PCV plugged?
Can you install a vac gage on an intake tap line?
Mass air sensor from original power plant or the yard?
Is the engine harness the old or new loom? - have you hand over hand checked the coil lines back to the firewall looking for pinched wires?

 

[rexington14]

Came on twice tonight and went into misfire protection mode. I'm at a loss here. I measured warmed up compression in 4 and 7 as well as 2 others and they all read 165 psi

Have you tried leaving it parked overnight in the roughest part of town with the doors unlocked and the keys in the car?

just a joke. sorry you are going through this.