Ecu misfire? (1 Viewer)

[TTO5]

2010 lx570. Got truck back yesterday after used engine install. Shop test drove it for a few days and I drove it home problem free (approx 20 miles,). As I pulled up to my house get a flashing engine light and can feel it misfiring. Codes po300, 304, 307.
Once it cools down to 160 degrees or less it doesn't appear until restarting it once it hits around 170 degrees it goes into misfire mode. Had it towed back to the shop. Shop called today saying everything checks out normally on their end but he decided to pull the ecu. He said maybe when ecu warms up it happens? He tried heating the ecu with a heat gun but misfire didn't return. Had it running 30 min or so with no issue. He thinks it's still the ecu but I never had an issue like this prior to the work done. He says it is unlikely that the harness wasn't plugged back in properly as the truck ran fine for a few days and the fact that it only does this once it's warmed up. My gut feeling says the harness ecu plug was causing this but not sure because of the way it only acted up once warmed up. Any ideas? He looked inside the ecu and everything looked normal in there

 

[TTO5]

Got the truck back yesterday . Shop test drove couple days, issue didn't occur for them after removing and re installing the ecu. Was fine on my 20 mile ride home last night. On the way to work this morning cruising 70 mph on highway engine warmed up the mil flashed for about 3 second then went away. I pulled up into a parking lot and the light started flashing again with misfire felt (codes po300, 304, 307). Wiggled some harnesses while the engine was running misfire didn't change. Shut truck off, re started right away mil on steady and engine smooth for about 3 seconds then back to misfire and blinking mil. Shut truck off for about 10 minutes, start back up and mil off no misfire until driving about 3 minutes after start up then back to misfire and flashing mil. If you raise engine speed to 1000 or higher when parked (trans in park position) feels smooth. Not sure what's going on. I'm having the toyota dealer where I work check it out to see if they can solve it rather then the shop that did the engine replacement (that shop is not a dealer they are an independent shop that works mainly on landcruiser/lx and range rover etc.)

 

[NikP]

Probably not wiring based on your post. Not sure if the engine swap did anything with coils or spark plugs. That's the obvious place to start. Swap the coil from another cylinder and see if things change (swapping coils is an easy diagnostic). If not, swap plugs with one that doesn't show a code or swap in new plugs.

 

[bloc]

Got the truck back yesterday . Shop test drove couple days, issue didn't occur for them after removing and re installing the ecu. Was fine on my 20 mile ride home last night. On the way to work this morning cruising 70 mph on highway engine warmed up the mil flashed for about 3 second then went away. I pulled up into a parking lot and the light started flashing again with misfire felt (codes po300, 304, 307). Wiggled some harnesses while the engine was running misfire didn't change. Shut truck off, re started right away mil on steady and engine smooth for about 3 seconds then back to misfire and blinking mil. Shut truck off for about 10 minutes, start back up and mil off no misfire until driving about 3 minutes after start up then back to misfire and flashing mil. If you raise engine speed to 1000 or higher when parked (trans in park position) feels smooth. Not sure what's going on. I'm having the toyota dealer where I work check it out to see if they can solve it rather then the shop that did the engine replacement (that shop is not a dealer they are an independent shop that works mainly on landcruiser/lx and range rover etc.)

Might be worth pulling the valve covers just to be absolutely sure you don’t have a broken valve spring. That sometimes presents as a misfire early in the failure.

 

[TeCKis300]

Been meaning to respond to help as this must be frustrating.

Sounds to me like there are some fuel trim or closed loop issues. The misfire is perhaps only a symptom and it's not due directly to ignition. With the delayed nature and your symptoms of it being smooth in certain RPMs, etc. Sounds like it could be a vacuum leak, and exhaust leak, or fuel pump issue, etc. It's not the ECU heating up.

Put an OBD-II reader and watch the fuel trims. Is the trims getting excessive when the symptoms occur?

Is it happening in a single bank or across both banks of cylinders? If it's both banks, it's more likely an intake/vacuum leak issue that affects both banks in closed loop. Or could be a fuel pressure/pump issue again affecting both banks. Basically the system if falsely responding to an issue/leak where it skews air/fuel outside of norms causing the misfire. The fact that it runs smoothly when cold is a good sign.

If it's isolated to one bank while the other banks trims are stable, then it's more likely an exhaust leak or O2 sensor related issue on that bank.

 

[TTO5]

Probably not wiring based on your post. Not sure if the engine swap did anything with coils or spark plugs. That's the obvious place to start. Swap the coil from another cylinder and see if things change (swapping coils is an easy diagnostic). If not, swap plugs with one that doesn't show a code or swap in new plugs.

Plugs are new. Coils are the ones that came on the used engine. I'll try the coil shuffle game and see if the misfire moves to a different cylinder. Thanks

 

[TTO5]

Been meaning to respond to help as this must be frustrating.

Sounds to me like there are some fuel trim or closed loop issues. The misfire is perhaps only a symptom and it's not due directly to ignition. With the delayed nature and your symptoms of it being smooth in certain RPMs, etc. Sounds like it could be a vacuum leak, and exhaust leak, or fuel pump issue, etc. It's not the ECU heating up.

Put an OBD-II reader and watch the fuel trims. Is the trims getting excessive when the symptoms occur?

Is it happening in a single bank or across both banks of cylinders? If it's both banks, it's more likely an intake/vacuum leak issue that affects both banks in closed loop. Or could be a fuel pressure/pump issue again affecting both banks. Basically the system if falsely responding to an issue/leak where it skews air/fuel outside of norms causing the misfire. The fact that it runs smoothly when cold is a good sign.

If it's isolated to one bank while the other banks trims are stable, then it's more likely an exhaust leak or O2 sensor related issue on that bank.

Ok it's cylinder 4 on one bank and 7 on the other. Maybe spray some carb cleaner around intake manifold while it's running? I gave them new intake gaskets to use after resealing the valley. My scanguage shows long term and short term trims. Which do I want to check and what are considered too high values? I can tell you as soon as it happens scanguage shows both bank a/f pinned at 18.09 but the shop told me normal to see that when it's misfiring. Do you think moving coils around is worth a check?

 

[TeCKis300]

If it's localized to those cylinders, yes, it's worthwhile to move coils around. As the issue affects both banks, I would rule out O2 sensors and exhaust leaks.

On a good running engine, trims really shouldn't exceed 10%. On occasion they can, but I'd say 18% is indicating there is a problem as the ECU believes it needs to compensate by adding a ton of fuel. I don't agree with the shops interpretation.

There isn't a single trim but a whole map of trims. It usually shows up first as ST trims. If the ECU sees that its systemic, it'll commit that to LT. So looking at both is useful. Does it show 18% at idle? What happens when you step on the gas? Do the trims go lower? Trying to assess if the trims are higher at idle than on load/speed.

I would look for intake leaks around and upstream of the throttle body. It's not likely the manifold gasket that would only show up in one bank unless both gaskets weren't installed right (unlikely). Could be the MAF too.

It surely could be the fuel pump or fuel system too.

 

[TTO5]

If it's localized to those cylinders, yes, it's worthwhile to move coils around. As the issue affects both banks, I would rule out O2 sensors and exhaust leaks.

On a good running engine, trims really shouldn't exceed 10%. On occasion they can, but I'd say 18% is indicating there is a problem as the ECU believes it needs to compensate by adding a ton of fuel. I don't agree with the shops interpretation.

There isn't a single trim but a whole map of trims. It usually shows up first as ST trims. If the ECU sees that its systemic, it'll commit that to LT. So looking at both is useful. Does it show 18% at idle? What happens when you step on the gas? Do the trims go lower? Trying to assess if the trims are higher at idle than on load/speed.

I would look for intake leaks around and upstream of the throttle body. It's not likely the manifold gasket that would only show up in one bank unless both gaskets weren't installed right (unlikely). Could be the MAF too.

It surely could be the fuel pump or fuel system too.

First off thanks for all this help. Today I moved coils 4 and 7 to different locations. Cleared codes test drove it. Once it heated up the mil came on flashing with misfire present. Codes stayed the same, 300, 304, 307
To Clarify the 18.09 is displayed for the a/f value not the trim. It is normal until the misfire starts. That's when it goes to 18.09 both banks. The short fuel trim goes to 0 on both banks during misfire I'm assuming because the computer shuts down fueling when it's misfiring? I can't see individual cylinder trims on my device only bank 1 and 2. The maf sensor is a couple Months old and was working fine with my other engine.
I sprayed brake clean around the throttle body and intake manifold with it running But didn't detect any change in engine speed. Not sure.Where else to go from here
I

 

[TTO5]

Some pics

 

[TTO5]

Another

 

[bloc]

Is it a Genuine Toyota MAF sensor or aftermarket? I’ve seen a couple posts over the years reporting problems with aftermarket, even new. And why was it replaced originally?

 

[NikP]

Attached is what the service manual outlines as the diagnostic steps for misfires.

Might check compression on #4 and #7 along with taking a look at the fuel injectors for those holes.

 

[TTO5]

Is it a Genuine Toyota MAF sensor or aftermarket? I’ve seen a couple posts over the years reporting problems with aftermarket, even new. And why was it replaced originally?

Genuine toyota. I work the parts counter at my toyota dealer

 

[gaijin]

I sprayed brake clean around the throttle body and intake manifold with it running But didn't detect any change in engine speed. Not sure.Where else to go from here
I

Genuine toyota. I work the parts counter at my toyota dealer

I would strongly suggest keeping the brake cleaner out of the throttle body - especially when the engine is running.

Since you work at Toyota, try using this instead:

Just a thought.

HTH

 

[TeCKis300]

Ah copy. Yes, O2 A/F will peg lean upon misfire (oxygen reaches O2 sensor due to no combustion).

Seems like STFT and LTFT aren't skewed when misfires happen? Both banks look good? If there's no large trims occurring, than it's not likely a closed loop fueling/compensation issue.

Might want to look closer at those two cylinders for anything that can affect air/fuel/ignition. Take a closer look at the harness and connectors. Could also be valve or headgasket issues.

 

[TTO5]

I would strongly suggest keeping the brake cleaner out of the throttle body - especially when the engine is running.

Since you work at Toyota, try using this instead:

View attachment 3756621

Just a thought.

HTH

I didn't spray it into the throttle body just around the outside of it to check for vacuum leaks. I would never spray it into the throttle body but good looking out. Thanks

 

[TTO5]

Ah copy. Yes, O2 A/F will peg lean upon misfire (oxygen reaches O2 sensor due to no combustion).

Seems like STFT and LTFT aren't skewed when misfires happen? Both banks look good? If there's no large trims occurring, than it's not likely a closed loop fueling/compensation issue.

Might want to look closer at those two cylinders for anything that can affect air/fuel/ignition. Take a closer look at the harness and connectors. Could also be valve or headgasket issues.

Jeez don't want to hear that as that's why I changed the engine in the first place. Oh boy

 

[TTO5]

I found some forum talk about crank position Sensors causing similar issues. Might that be it?

 

[TTO5]

The shop that did the work suggest trying to reset the ecu? Anyone know how to do this?