LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

Rough Idle After Muffler Delete

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Old 12-04-17, 06:02 AM
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Cestine74
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Default Rough Idle After Muffler Delete

Hey everyone,

New to the page, and a bummer I'm introducing myself under these circumstances..
Yesterday I cut off my 4 mufflers on the car so I could really hear the engine, and I did not remove any cats or (to my knowledge) O2 sensors. The car is not giving me any check engine lights but it developed the issue where it will misfire and "sputter" at low RPM. When braking and coming to a stop the car literally bucks back and forth from the inconsistency in the "Bang" portion of the cycle. I'm not sure if just welding in a full exhaust from where I cut the original will help, or if it is a bigger issue. Again, no check engine lights (yet) but it loses power when accelerating in the low RPMS. Could cutting the exhaust have altered something to do with the way the ecu reads the ignition or air/fuel ratio?

Please help!!!
Old 12-04-17, 06:53 AM
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Scraape
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Originally Posted by Cestine74
Hey everyone,

New to the page, and a bummer I'm introducing myself under these circumstances..
Yesterday I cut off my 4 mufflers on the car so I could really hear the engine, and I did not remove any cats or (to my knowledge) O2 sensors. The car is not giving me any check engine lights but it developed the issue where it will misfire and "sputter" at low RPM. When braking and coming to a stop the car literally bucks back and forth from the inconsistency in the "Bang" portion of the cycle. I'm not sure if just welding in a full exhaust from where I cut the original will help, or if it is a bigger issue. Again, no check engine lights (yet) but it loses power when accelerating in the low RPMS. Could cutting the exhaust have altered something to do with the way the ecu reads the ignition or air/fuel ratio?

Please help!!!
hmm, funny cuz i deleted my 2 rear mufflers yesterday, but i am not having this issue.
Simplest thing you could do is unplug the negative battery terminal for like 15 min and plug it back in and drive around and see if there's any difference

Last edited by Scraape; 12-04-17 at 11:03 AM.
Old 12-04-17, 06:56 AM
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Cestine74
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Okay Scraape, I'll give that a shot. Just based on the way it was acting it seems like for of a fuel mixture issues, so resetting the ECU so to speak may fix it.
Thanks!
I'll keep you posted
Old 12-04-17, 09:29 AM
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timmy0tool
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I've done a muffler delete but only the rear mufflers not the inner two with no problems. of course you'll experience a lack of backpressure which will equate to a loss in power (hard to tell from the seat) but it should in theory not affect the way the engine runs as you only altered the parts after the secondary o2s.

an ECU reset is a good idea to start. I would definitely consider extending the pipe to the rear of the car not only to restore a little bit of the backpressure but also to vent the exhaust away from the cabin. that stuff is just a tad toxic !
Old 12-04-17, 11:21 AM
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Cestine74
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Thanks for the advice guys,
Unfortunately resetting the ECU didn't yield any good results. Thinking that I definitely need to follow the exhaust out the back, as well as check for vac leaks and check my coil packs. These are really the only things that seem logical to me as being the source of my issue.
The misfiring appears to be intermittent, but becoming more apparent after the engine is warmed up. At first it seemed to be doing it only at idle, and now it misfires almost constantly through the rev range.

Any other ideas?
Thanks
Old 12-06-17, 06:29 PM
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Moarpower
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Wait...did you literally just cut the exhaust before before the mufflers?? Did you not ad pipe to those sections? If you just deleted it at the first muffler set it will run like **** mate.
Old 12-06-17, 11:17 PM
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Sounds like mine did. You will melt your catalytic converter if you drive it lie that. Check all plugs and leads.
Old 12-07-17, 01:23 PM
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PureDrifter
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likely unrelated, troubleshoot fuel and spark as usual.
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