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Exhaust Leak Causing Loss of Power

Explorin'VA

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I just swapped transmissions and while doing so I had to remove the entire exhaust up to the manifolds. The y-pipe to manifold bolts were seized on, so to keep things rolling I cut a section out of the y-pipe. After everything else was done I took it to a mechanic to get the pipe welded back together and he said he couldn't do it without removing the manifolds. I didn't want to pay to have that done so I ordered a new replacement y-pipe. I was able to remove the two inner y-pipe studs from the original pipe, but the two outer studs wouldn't budge. I ended up cutting them off and drilled out the hole on the passenger side, but there was not a lot of room to work on the drivers side and I broke a cobalt bit off inside the stud. So on the drivers side down pipe I'm only using one of the two bolts needed on that flange and I can hear and feel air escaping. It runs but it stumbles during idle and it looses power at high RPMs. It feels like it wants to drive, but when I hit the gas it just boggs down and I hear the air leak hissing. The aftermarket y-pipe didn't really fit right. It hit the transmission so I had to reshape it a little. This pipe just might not seal as well as the oem one. Is there any kind of gasket I can use to seal it up? I was thinking about putting a clamp on the flange to hold it tight. Just wondering what your opinions are on what to do here. Thanks!
 
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EMBRACETHEHATE89

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Mine has a pretty severe exhaust leak that i cant seem to find and it runs great just has that annoying TICK! I think your issue is definitely something else.
 

2stroke

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It depends on where the exhaust leak before an O2 sensor, especially a bad leak on just one side can cause all kinds of problems.
 

EMBRACETHEHATE89

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Blown header gaskets in my boat, never had a loss of power.....didnt sound good and its not good for a hipo motor. So i still think its something else. I wish i could trace my leak, but i cant. Probably just going to replace everything anyways....

Id check the plug wires, maybe one slipped off a bit while installing everything....
 

vq5speed

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Take it to a muffler shop maybe they can torch that stud out. Or maybe weld on some new tabs to make some brackets that can pull the two pipes together with a bolt. Or he may come up with some other idea
 

Explorin'VA

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I drove around with the o2's unplugged and the hesitation stopped. I found clamps made for broken manifold studs so I ordered one and it will be here today.
 
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Explorin'VA

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I put a clamp on to seal up the leak and the truck still runs like crap. I'm hoping the timing chain didn't jump a tooth. I accidentally rotated the crankshaft backwards when removing the flexplate during the tranny swap. Could this mess up the timing? I also unplugged a connector during the swap by accident. Turns out it was a fuel injector harness. I connected it back up but maybe i didn't lock the harness in all the way? I'm going to check all the plugs and wires first because I did remove them before I removed the old flexplate. I thought I put them back on the right way but who knows.. Also why would my CEL come on when the truck is on but not flash any codes when I go to check them?
 

4wheeltom

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If it runs good with the O2 sensor unplugged I would replace it, could could be sending bad signals to the computer and making it run super lean.
 

natenkiki2004

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It's virtually impossible to jump a tooth unless something breaks in the timing gear assembly. Take a look:
https://dl.dropboxusercontent.com/u...Explorer/Pictures/Engine Removal/P1020138.JPG

It definitely wouldn't affect timing if you rotated the engine backwards. Heck, I think I did that several times when lining up the bellhousing and getting after the torque converter nuts.

Definitely check the plugs & wires, that could easily be the issue. Oddly enough I had a misfire that got worse and worse about 200 miles after putting everything back together. Bugged the crap out of me but the plugs looked great and even. Turns out a spark plug wire, not even a year old, had lost continuity. These were premium Belden wires. It must have been poor manufacturing or we got rough with it when yanking the engine out.

Not sure on the CEL, are you checking the codes right?
 

Explorin'VA

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Yes I'm using the paperclip method. As long as I've had the truck it's had some sort of engine code, but now it's not flashing any codes at all. With the o2's unplugged it doesn't stumble as much while I accelerate but the engine occasionally shuts off if I throw it in nuetral while coming to a stop. It's also way down on power. I can still hear air hissing when on the gas pedal but I think that may just be the air filter. I'll go ahead and replace the o2's. Rockauto is half the cost of the parts store so I'll order from them, just have to wait a few extra days for the sensors. Are the left and right o2 sensors on a 94 the same part? I noticed some companies list a different part number for each sensor, while others don't.
 

EMBRACETHEHATE89

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Like i said earlier, i think you have way more issues then a exhaust leak. If its way down on power id run a compression test and see what ya got. Also if you are hearing a hissing, check that all the spark plugs are nice and snug.
 

Explorin'VA

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I'm just thinking of what I've done recently to it that could have caused this. I replaced the y pipe and painted it inside and out. Maybe the chemicals from the paint messed up the o2's. But I will do a compression test and see what that tells me.
 

EMBRACETHEHATE89

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Sometimes weird stuff happens. Damn gremlins HAHA good luck!
 

fritz24

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You have an exhaust leak and you are going to change O2 sensor just because it runs better when its unplug????The o2 sensor is doing its job because it detects a lot of oxygen inside the exhaust system and maybe you have a lean condition right now. You mentioned "lost of power", im not familiar with 1st gen but is you vehicle have a knock sensor?
 

Explorin'VA

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I see, it could be something else and the oxygen sensors are just doing their job. I've cleaned the maf and iac. I need to find out the codes to point me in the right direction. I don't think I have a knock sensor.
 

fritz24

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If you want proper diagnosis Fix the known issue -the exhaust leak. Running lean can cause all the symptom you have right now. From here you can eliminate other symptoms because vac leak(you mentioned a hissing sound)and exhaust leak usually have similar issue.
 

Explorin'VA

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I have fixed the exhaust leak, checked that my vac lines are connected, and cleaned some sensors with the same results.
 

fritz24

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Did you verify the fix with a smoke test? Visual is not enough to say you fixed the issue. Ive got the same issue with my ex before, found the vacuum hose going thru the brake booster is loose and causing a leak but that doesnt solve the problem. Ended up it was my spark plug wire that has a very high resistance that causing a slight missfire or feels like stumbling during idle. If youre sure about the fix, check these three things: air intake system including maf, ignition, and fuel delivery.
f.y.i. engine oil dip stick that is loose can cause also cause this issue.
 

4wheeltom

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You have an exhaust leak and you are going to change O2 sensor just because it runs better when its unplug????The o2 sensor is doing its job because it detects a lot of oxygen inside the exhaust system and maybe you have a lean condition right now. You mentioned "lost of power", im not familiar with 1st gen but is you vehicle have a knock sensor?


If the O2 is sensing extra oxygen it would think that the engine is running lean causing the computer to richen the mixture which wouldn't cause a power problem but would cause poor fuel mileage. When the O2 is unplugged the computer will go into a default mode that make it run full rich.
 
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MayJan

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Just as a thought, if you're hearing a hissing noise, I'd say it's vacuum related. And if you're losing power, it could be fuel delivery related. That said, I'd check the vacuum line on the fuel pressure regulator. It's a little hard to see, but the line is on the front passenger side of the engine, kinda below the fuel rail. It would cause the exact same symptoms as you are having. Had the same issue a couple years back, and it drove me NUTS for about two weeks straight! Good luck with it!
 
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