P0135 Code / Live Data Open loop

[watertownfj]

Hey everyone. 1997 LX450
I’ve gone through other threads on this and I’m not finding much that people have solved this problem or I’m not reading the threads properly.
Truck runs perfect in cold starts but once it warms up it starts idling a little rough and when driving, it’s chugging while trying to get her going. Looking at live data, I’m seeing the fuel system isn’t changing to an open loop for one. Also reading misfire on cylinder 4. I’ve replaced the EGR, both o2 sensors, checked all my hoses etc. I did purchase a new ETC SENSOR but it looks miserable to get to. It is reading proper temp in live data so I’m assuming it’s not the Problem. I’ve checked wires as well. I’ll keep working on it but I’m stumped and want to be driving this thing. FYI. It started doing this into a long cross country trip so she was running hard for a couple weeks.
Thank you

 

[alia176]

This statement confused me:
I’m seeing the fuel system isn’t changing to an open loop for one.

Our fuel system goes into closed loop pretty quickly after starting up. As soon as the heater in the O2 sensor warms up, the system goes into closed loop operation and starts controlling of the air/fuel ratio by controlling injector duty cycle. Someone correct me if I'm wrong.

Misfire on #4 could also point to #4 injector. Have you tried swapping the injector with another one to see if the misfire code goes to the new cylinder? Also, make sure the ECU harness portion that goes by the EGR pipe is ok and not partially melted. Some of us had this issue and some folks wrap this area with heat tape.

Also, check for vac leaks by conducting a smoke test using a smoke test machine. You may have a vac hose that's relaxing after the engine bay is warmed up. Have you replaced all vac hoses under the upper intake manifold? These are a PITA to get to and often overlooked.

 

[watertownfj]

Yes, it’s supposed to go to a closed loop after it heats up. When I look at live data on the code reader, it says at OL. It doesn’t switch to CL.

 

[watertownfj]

I haven’t replaced any hoses yet. Just checked them.

 

[watertownfj]

Yes, it’s supposed to go to a closed loop after it heats up. When I look at live data on the code reader, it says at OL. It doesn’t switch to CL

This statement confused me:
I’m seeing the fuel system isn’t changing to an open loop for one.

Our fuel system goes into closed loop pretty quickly after starting up. As soon as the heater in the O2 sensor warms up, the system goes into closed loop operation and starts controlling of the air/fuel ratio by controlling injector duty cycle. Someone correct me if I'm wrong.

Misfire on #4 could also point to #4 injector. Have you tried swapping the injector with another one to see if the misfire code goes to the new cylinder? Also, make sure the ECU harness portion that goes by the EGR pipe is ok and not partially melted. Some of us had this issue and some folks wrap this area with heat tape.

Also, check for vac leaks by conducting a smoke test using a smoke test machine. You may have a vac hose that's relaxing after the engine bay is warmed up. Have you replaced all vac hoses under the upper intake manifold? These are a PITA to get to and often overlooked.

i should have said it is not changing from an open loop to closed loop.

 

[alia176]

Yes, it’s supposed to go to a closed loop after it heats up. When I look at live data on the code reader, it says at OL. It doesn’t switch to CL.

ok, that makes sense. Thanks for explaining!!!

 

[goneloco]

Sounds like the exact issue I am having. Did you figure it out?

It is so weird because when cold it runs great. When it warms up it misfires during moderate acceleration so I have to floor it and it runs good. So hard on and off the throttle all the time in traffic. When cruising on a flat road it runs great. How is this possible. I am thinking it maybe the ECU... Love to hear if you got this solved... Thanks

 

[Gomgwtfbbq]

+1 to this thread, trying to track this same issue down on my 96 off and on for the past 6 months. (not my daily driver)

I get readings via OBD2 reader (torque app) for both O2 Sensors, ECT, MAF on a cold start and it runs great. as soon as it warms up it starts to stumble all over it itself like what is mentioned above. Once its warm, I NO LONGER get any readings from O2 Sensors, MAF, or any ShortTerm and LongTerm Fuel Trim readings. Its like its trying to go into closed loop, but since the data isn't there it doesn't know what to do.

I've thown new o2 sensors, new ECT, new fuel filter and fuel pump relay all because they were cheap and of unknown age to me. No real change. At this point I'm out of ideas other than maybe tracing each wire in the harness or swapping ECU.

 

[Malleus]

Check the considtion of the engine harneess near the EGR pipe, directly above the #6 injector.