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New member, please help. 89 gt new exhaust running rich.

885 Views 6 Replies 4 Participants Last post by  Smurf stang
i have an 89 gt with a few slight mods. it has a cam, cold air intake, msd coil, 3 row radiator, and an electric fan. this past week I had my new exhaust put on. it consists of mac 1 5/8" long tubes, 3" catless h pipe, and 3" cat back. Before the exhaust was put on, the car ran perfect. after the exhaust, the car ran rich. I was able to smell fumes when I was idling and sometimes when I drive. one of my buddies recommended swapping the 02 sensors for heated 02 sensors. he said that the 02 sensors required a specific amount of heat from the engine that got reduced when the long tubes got put in. need some help. any recommendations?
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The MAC long tubes should have the sensor bungs welded into the collectors. Is that the case? If so, I think they are close enough to the original location that they shouldn't give you too much of an issue. You may get momentary rough idle upon initial start up or maybe a little longer period of rough idle when it is really cold, but you shouldn't need a tune for your combination just because you put headers on.

Heated sensors will not generate enough heat to compensate in open-loop mode if this is truly a lack of heat in your exhaust issue. Further, your sensors are heated - if you doubt it, unscrew one, let it hang, turn the ignition to run, and touch it. It will be hot.

The key is that you want your o2 sensors about 15-16 inches or so from the head. This is due not only to the heat issue but also the table in the EEC that controls when they sample. Not only do they need to be the correct temp, they also need to be looking at the exhaust at the proper time. Distance away from the head can affect both things.

If you don't have ceramic headers, try wrapping them...?
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