Ever since I installed my new exhaust system(new Header to tailpipe, including a new O2 sensor,) my idle runs strange right after it is warmed up. It goes from 1500 to 1000 in a rythm of 1500 for one second to 1000 for not even a tenth of a second then back up to 1500 for one second. Like a vroooooooooom-----vroom-----vroooooooooom-----vroom------etc.


This is only after it is almost warmed up. it's like an "in between" before the fast idle is completely kicked down. My truck is a manual tranny(22R-E), 1989.

This does not affect how the truck runs. in fact, it runs better. Im guessing the O2 sensor is the most probable cause. Any wisdom on this?

 

Does it do this all the time at idle or only when you are stepping on the brake pedal? If it happens with the brake pedal it is a very common problem with 22re engines.
But since the problem only came after the new exhaust you might just have a small leak on your headers. That could cause for weird symptoms. Here's how you check it, you need to submerge it like you used to do with you bike tires to check for flats. So find a nice deep lake to check it out. Matter of fact that's what I was doing in my pic.
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Unfortunately, they only way I can do that here in northcentral montana is to drive off a bridge, crash into water, and hopw i can get out somehow. I noticed that my cat is leaking and it needs a new gasket, so im certain that is the problem. But, at zero degrees and a foot of snow, Im gonna live with it for a while.

There is unfortunatley no shop to access for free.