BobMax

I replaced the exhaust system on the '98 with a Bosal system. Not long after, I got a P0138/P0139.

The Bosal puts the oxy sensor in a much more direct path on the pipe. Figuring that was the issue, I got a 90 degree extender that puts the sensor about 2" total from the pipe (but it's full diameter inside). I also got a new Bosch sensor as I didn't want to fool with this repeatedly. Reset the codes.

Unfortunately it popped the code again in a few hundred miles. Reset it again. Got it again in a few hundred miles.

I didn't abuse the stock wiring and the sensor wiring is new.

One thought I had is that maybe I put the cat in backwards. There didn't seem to be any real indication which way it goes and it can install in either direction, but there is a "knub" on one end that might indicate something.

Another thought is that perhaps the cat is bad. I did have to drill out the studs and that took some oil around the studs, but I was careful not to get any inside the cat. If any leaked in, it would have been a tiny amount. But's it's possible a drop made it in.

Ideas? I could replace the cat, but it seems like a crap shoot. Also, I know some aftermarket cats throw codes anyway. I don't like throwing parts at it either. But, I only get to work on this car a couple times a year and I need to solve this in the next month before it goes away again for a long time.

Any ideas on what to try? I need the code off to pass inspection here and it's coming up in a month.

maxima297

Get a Denso o2 sensor. Bosch is just a cheap alternative and in my experience, sucks. Also, check the o2 sensor fuse.

BobMax

Thanks... fuse is a good idea. Any idea which one?

I replaced the Denso sensor that was working before the exhaust replacement because of the codes afterwards. I suppose it's possible that the Denso would work with the extender on there (curing the Bosal placement issue).

DennisMik

iTrader: (2)

Fuse # 34, 15 amp, is in the right hand column, 8th slot from the bottom (count empty spaces).

maxima297

Just out of curiosity, why did you choose to go with Bosal over the Tenneco exhaust parts?

BobMax

Well, take a look at the welds on this Walker/Tenneco replacement for the cat mount pipe: http://www.walkerexhaust.com/catalog...g-lookup/51042

I can't believe they even put that photo in their catalog. I welded better than that self-taught with a cheap arc welder in high school.

OTOH, Walker actually does list the pipes correctly. Bosal has a catalog problem with the various configurations. I worked with a rep there to figure it out and he fixed some of it, but it's still not right. They don't understand the o2 post-cat configuration and Federal/CA differences. I tried :-(

maxima297

I noticed that when I was pulling the parts for mine last month. I had the intermediate pipe shipped over from the warehouse just in case I need it when I install the cat. It's pretty sloppy. I don't like how they did that. But, Tenneco is my only option up here unless I want to pay more and wait longer for Bosal pieces.

M in KC

I did a full Walker system a couple years ago and short of the post cat O2 sensor's bung orientation on the Walker midpipe my systems is good and tight. I eventually went back to mother Nissan for the O2 sensor midpipe. Crazy they are forging this part now not a welded up part from Nissan but it corrected the O2 sensor fitment issue with the Walker part. No codes before or after the full Walker system install with new O2 sensors NGK's as I recall. Mileage ticked up 4-5 mpgs as well after install.

komik

OMG those are some nasty welds.

To your original question though, couldn't you clear the code again just before taking it for inspection if it stays off for a couple hundred miles? I know that's not a fix, but it would buy you some time.

My Max won't pass inspection because of a CEL caused by the missing rear O2 sensor that was cut off when the cat was stolen. My registration and inspection expired in September of 2014, so I peeled the stickers off the window and threw them away. So far so good. I plan on fixing that one of these days.

CS_AR

Can you use the original post cat part where the O2 sensor bung is located with a Walker or Bosal system?

One of mine was in decent shape when I installed the WS Y-pipe and Magnaflow cat a few years ago. I felt like I needed to keep it. So I cleaned it up and hit it with some VHT header paint to keep it from rusting. It seems like a heavy part that should hold up for a long time.

I think I need to get an O2 sim because I get a P0420 with that high-flow cat about once a month.

BobMax

I been thinking of that. I can have one not-ready condition to pass so I might be able to time it to get everything ready except the O2. But, I would really rather fix it so that I know where there's an actual problem since the car is remote from me most of the time and the driver unskilled in repair. If something else triggers the CEL I'd like to know.

Unfortunately Bosal makes the cat mount pipe and rear pipe as one unit.

Do those work? That might be a solution.

CS_AR

Are you getting any white smoke from your exhaust system?

Can you smell un-burned fuel coming out of the exhaust?

Is the car taking a little longer to start than normal?

Is your car a CA or Fed spec version?

Codes P0138 and P0139 can be caused by a failing O2 sensor, or too much fuel from a leaking injector. How old is the O2 sensor? Like others have posted above, I would replace the O2 sensor.

I need to use an O2 sim because I get P0420 that indicates that O2 sensor is getting too hot. The high-flow cat allows to much high temperature exhaust gas to with the O2 sensor and causes the P0420 codes.

If you someday use a high-flow cat and get code P0420, there are O2 simulators like Weapon-R and Vibrant that work using the principal of removing the sensor tip from direct exhaust flow so it runs cooler and doesn't report a bad cat.

Right now, I would trade your problem for mine. I've fixed P0138 and P0139 codes by replacing a faulty O2 sensor.

BobMax

CS:

There IS an occasional hard start. No on the unburnt fuel (raw gas) smell at least from within the passenger compartment. None at all. It's cold now, so the smoke is hard to judge.

I believe this car is Federal, but there's no indication on the sticker. I went down a long road trying to figure that out officially. But, it was originally sold in GA so that likely would be Federal. It only has 2 oxy sensors, not 4.

The O2 sensor was replaced due to this problem. I can restore the original as a test but I'm guessing that's not it unless the Bosch doesn't work (I've had good luck with them elsewhere but I know some cars are particular).

I am already using a right angle extender that has the sensor 2" from the pipe. I'm thinking of putting a washer in there to reduce the opening to a minimum amount. Thoughts?

BobMax

Also... is there a particular direction the cat has to be installed? By the time I got the studs drilled out in the shop and got back to the car, I wasn't certain which way it came out. It fit either way.

CS_AR

IIRC there was a thread where the question was asked about direction. Unless there are directional arrows to the contrary, then I don't think it matters.

If you tried running it without the extender? I've read about people who installed the O2 sim extender that actually start getting codes like the O2 sensor was not working. Unless you are using a high-flow cat where the O2 sensor gets too hot and causes a P0420, I can see how the O2 sensor may not getting a good reading if used with a regular cat.

California cars have 4 O2 sensors, where fed cars have 3. There are 4 plug sockets on the coolant pipe that runs across the side of the engine closest to the radiator for a CA car.

BobMax

Yeah, it's Federal then. It doesn't have the four connectors in front like my '99 did.

I originally installed the factory sensor into the pipe. I got a code after 200+ (not sure) miles. So, I added the extender AND replaced the sensor. Still got the code after about 300 miles.

BobMax

I think I finally fixed it... 400 miles with all sensors ready since about 50 miles and no codes yet!

As I've mentioned before, I only get to work on this car for short periods of time spread far apart, so I decided to try both "last options" at once... as a result, I can't say which one cured it.

I installed a new Bosal cat. That may have cured it.

I also took the 90 degree extender I had already installed (http://www.ebay.com/itm/M18x1-5-90-D...-/111752734060) and I installed a thick aluminum spacer in the threaded end (something like this https://www.aluminumspacers.com/). The one I had on hand was a little large, so I ground the OD down to where I could force fit it with my press (read: large ball peen hammer) into the threaded end's hole. I drilled the ID hole to about 1/4".

Between the two, it seems to be working.

CS_AR

Great news!

That elbow extender looks better than the Weapon-R I recently purchased. Very nice piece.

My son brought brought me one of the aluminum spacer to fit in the end of the elbow spacer. He started drilling it out then got busy with a neighbor who is installing a clutch in an Accord. The weather turned bad then snowed.

What type of distance did the aluminum spacer add from the O2 sensor's tip to the opening inside the elbow as in 2", 1", 3/4", 1/2"?

Something like this?

BobMax

Keeping in mind that that 90 degree extension already pushes my O2 sensor a couple inches from the exhaust pipe fitting... the aluminum "spacer" is basically just a very thick washer, reducing the hole in the end of the short arm of the O2 extender from 1/2" or so where it enters the exhaust pipe to a small hole 1/4" in diameter.

The "spacer" (thick washer) I drove in there was about 7/16" thick. About 1/8" ended up inside the O2 extender fitting and the rest inside the exhaust pipe.

So, the gases have to enter a 1/4" hole though the 7/16" spacer, then they travel into the straight part of the extender, round the corner, and then get to the O2 sensor.

Make sense? I should probably draw something, it would be easier to explain. FYI - that fitting is top quality and stainless. After running six months it still looked brand new. If you need one and the length / angle works for you, I'd get that one.

CS_AR

Makes sense to me, I was thinking about approaching it from the long end of the elbow. Let me look at it from this angle.

BobMax

I was thinking that originally too, but I couldn't figure out a way to secure a washer inside the tube I had to limit flow. The threaded end was easy for a press fit from the outside.

BobMax

And then the bad news... code came back at 790 miles. that's way beyond the usual 200-250 miles that was setting it before the last mods, but it still came on. After a reset, it cam back at 340 miles.

At this point the cat is new, the o2 sensor is new, there's a right angle extender on there, and there's a limiter in the extender. I'm thinking it's time for an electronic simulator.

CS_AR

Thanks Bob for the update. I got into this yesterday on the 99 model. I tried to install an extender and the elbow without removing the B-pipe. No luck on that. Weather started getting bad so I had to quit for the day. So I think I will just move in a decent OEM cat from another car. I figured if I go to the trouble to remove the B-pipe, I might as well just swap out the cat.

BobMax

I think I'm stuck with the electrical solution. I will need to fix this in a one-week time frame and won't have time for testing - otherwise I'd be trying a bunch of other combinations and angle and limit fittings.

Does the in floor wiring for this run internally from the floor entry back to the computer? Or is there another external connector in front of the engine for the cable?

CS_AR

This guy in the video shows how to fix a P0420. No idea if this will work for a P0138 or P0139 or our 4th gens. I've read where there are electronic O2 sensors are for sale on the internet that plug in to the sensor harness. I would buy one if I knew there was an electronic one that worked.


https://www.youtube.com/watch?v=qHD7T7EhuzI

BobMax

I will have to watch that. I also spotted this: http://www.toyota-4runner.org/3rd-gen-t4rs/175242-how-make-your-own-rear-o2-simulator-$5.html