Exhaust leak help!!!

[Miyota]

Hello everyone here. Looking for a little advice on my 2000 4runner limited auto with 285's on it. So about two weeks ago I developed a pretty good exhaust leak do to the pipe rusting through where it's welded to the flange. This truck is California emissions and it was the muffler side just after the dual cats. So I ordered a cat back exhaust from rock auto and gaskets. The mating flange on the cat side was not a flat surface due to rust so I cleaned it the best I could and used rtv as well as the gasket. All is good there I don't here any leaks there anymore. The issue being when the leak first popped it my truck starting shifting really oddly. It would almost shift to early and drop to really low rpms leaving me with no power and if I gave her the gas it would snap into a lower gear and throw a engine light for shift solenoid E. Now after the cat back exhaust it's a lot better but still struggles from time to time. I replaced my solenoids about 2 months ago, added a B&M cooler, and used valvoline synthetic fluid. I'm not low on fluid or anything. So the question out of all of this is could an exhaust leak cause these symptoms and is there a chance it's leaking somewhere else causing it to still act up or is this a transmission issue? Any help appreciated.

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[Konkordmusk]

My best guess is simply: coincidence.
However, you only had the one code for the transmission? Were there any others? I would reset the ECU/clear the codes and see how the truck behaves after that, and report back.

 

[thegipper]

I would see if your cat is clogged. My grand prix was running sluggish and shifting really weird and it was because my cat was clogged. Once I installed a new one, the car shifted perfectly and sluggish behavior was gone.

There are a couple ways you can test it. The first by removing the upstream 02 sensor before the cat. Keep the electrical harness plugged it but remove it from the exhaust. This will allow the exhaust gases to easily escape from that port. Take it on a drive and see how it runs. If it still runs/shifts like crap, its not the cat.

The second, is to use a infrared heat gun. See how hot it just before and after the cat. If it is hotter after the cat (towards the muffler end) it is working the way it should and is not clogged. If it is hotter on the engine side (before the cat), then it is clogged and needs to be replaced.

I'm not sure why a clogged cat would make the tranny shift funny but it happened to me. I have also read several other accounts of people having tranny shifting issues and it ended up being a clogged cat although it usually starts with a sluggish running engine.

https://www.youtube.com/watch?v=n0Hx2zjVodY

 

[Miyota]

So update on my issue. I had a friend help run some tests as you guys suggested and come to find out the new muffler was leaking along the seam of the casing. That was the only thing we could find wrong. So I called up and got a replacement. The seam on the new one actually looked crimped this time. I pulled the old on off and the second cat (I have California emmisions) and used all new gasket and some exhaust sealer from napa. Fired it up and let it run in the driveway for a good half hour. Checked it all out and found no leaks. I am on day two and have had no CEL or shifting issues. I can't believe that an exhaust leak would cause the transmission to act up and throw codes but it is was it is.

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[thegipper]

Did you happen to test the cats to see if they were clogged? Since you removed that second cat, it may have been the one that was possibly clogged. I have never heard of a exhaust leak causing it to run sluggish and shift weird but it is definitely not uncommon for it to exhibit these conditions with a clogged cat.

Removing that second cat that was potentially clogged is most likely the reason why the problem is gone now.

Either way its fixed so that's good!

 

[Miyota]

I removed it just to change the gasket. I tested it and it was fine.

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[nsahk]

I'm having a similar problem with my 96 4Runner. The engine revs also get really low when it changes down gear coming to a stop. 500rpm or so, and the drivetrain shunts.

I sent you a PM.