Replaced muffler, then O2 Sensor Fail, then misfire. Connected? (1 Viewer)

[formyper]

Hi all,

About two months ago, I replaced the muffler and resonator (Northeastern stainless steel) on my 2000 lx470. I had a lot of trouble getting it to mount up properly, and am still not sure all the connections are seated 100%. After I replaced the muffler, I took the cruiser out and immediately got a code P0135, drivers side upstream O2 sensor. After determining that it wasn't critical, I made plans to replace later. Let the cruiser sit mostly unusued for 2 months or so, got lazy about changing out sensor, then used cruiser to haul a bunch of mulch in trailer (about 3000lb each time). The day after that, when driivng with family, notice shuddering, severe lack of power. Pull over, have the car towed back to the house, check codes and see P0303, misfire on Cylinder 3.

I'm wondering if I didn't install the muffler properly, causing the upstream o2 sensor to fail, which then caused the misfire. I am planning to replace the upstream o2 sensor, cylinder 3 coil pack and plug. Should I be looking at the exhaust system too? Should I make sure that is fixed before replacing the sensor and coil, or is it just coincidence that all this is happening at the same time?

Thanks in advance,

 

[AlpineAccess]

Was it welded in?

 

[joshAUST]

I'd check the wiring to the upstream O2 sensor.
Possibly got damaged during the muffler install?
Just a guess, an I am not an expert at all.
Shouldn't cause a misfire though...
although, if the O2 sensor is providing incorrect or no information, the system could be running excessively lean or rich, and could cause a misfire.

 

[2001LC]

Muffler R&R, most likely had nothing to do with upstream O2.

It is more likely you have a issues with cylinder #3 (plug and or coil), effecting O2.

I'd start by inspecting #3 coil & spark plug.

Ticking time bomb TICK TICK TICK: Spark plugs Alert Alert Alert!

TICK TICK TICK POP POP POP is a ticking time bomb, often mistaken as exhaust manifold crack or gasket leak leak. ALERT, ALERT, ALERT: Spark plugs are working themselves loose. "Walking Out" Then blowing out of head, taking their female threads of head with them! Very damaging! You think TICK...

forum.ih8mud.com

 

[formyper]

Was it welded in?

No, not welded in, just bolted in with new crush rings

 

[formyper]

Muffler R&R, most likely had nothing to do with upstream O2.

It is more likely you have a issues with cylinder #3 (plug and or coil), effecting O2.

I'd start by inspecting #3 coil & spark plug.

Ticking time bomb TICK TICK TICK: Spark plugs Alert Alert Alert!

TICK TICK TICK POP POP POP is a ticking time bomb, often mistaken as exhaust manifold crack or gasket leak leak. ALERT, ALERT, ALERT: Spark plugs are working themselves loose. "Walking Out" Then blowing out of head, taking their female threads of head with them! Very damaging! You think TICK...

forum.ih8mud.com

Thank you! Ive purchased a denso coil and plug and a O2 sensor. will replace those, torque to 18 lb ft, and report back. truck is at 178k, original plugs and coils as far as i can tell. took a look at one coil after purchase @168k, looked to be in good shape, do you think i should just replace them all so they don't die far from home? or just carry a few replacements with me

 

[formyper]

I'd check the wiring to the upstream O2 sensor.
Possibly got damaged during the muffler install?
Just a guess, an I am not an expert at all.
Shouldn't cause a misfire though...
although, if the O2 sensor is providing incorrect or no information, the system could be running excessively lean or rich, and could cause a misfire.

that was my thinking. exhaust was leaking, maybe that melted something?

 

[2001LC]

Thank you! Ive purchased a denso coil and plug and a O2 sensor. will replace those, torque to 18 lb ft, and report back. truck is at 178k, original plugs and coils as far as i can tell. took a look at one coil after purchase @168k, looked to be in good shape, do you think i should just replace them all so they don't die far from home? or just carry a few replacements with me

Coils do weaken with use. Excessive Heat, seems to do the most to weaken. A loose spark plug will cause excessive coil heat. Where as replacing all coils can improve performance. It is not generally needed at 178K miles.

If spark plugs have not been replaced. I would replace those.

 

[formyper]

Just an update - I removed the coil and plug and it looked like this inside. Could that be a bit of anti-seize at the bottom?

I replaced the coil, which still looked pretty good. It doesn't have the denso label on the top, so I think was wrong and it's not original. Spark plug was ngk, also looked pretty good. Replacing those two fixed the misfire. THen changed out the upstream drivers O2 sensor, which came out nice and easy with an adjustable crescent wrench. Everything seems to be working fine, have an order in for more plugs will leave in car for now and change out when I have the time.

 

[AlpineAccess]

Just an update - I removed the coil and plug and it looked like this inside. Could that be a bit of anti-seize at the bottom?View attachment 3335223I replaced the coil, which still looked pretty good. It doesn't have the denso label on the top, so I think was wrong and it's not original. Spark plug was ngk, also looked pretty good. Replacing those two fixed the misfire. THen changed out the upstream drivers O2 sensor, which came out nice and easy with an adjustable crescent wrench. Everything seems to be working fine, have an order in for more plugs will leave in car for now and change out when I have the time.

Looks like it could have been a little blow by from a lose plug (less likely) or a spark tube gasket letting some oily crankshaft gas through (more likely). Neither are really a big deal if the plug came out easily and the new plug went in smooth.