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

884 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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really the car needs to be "tuned"..any dyno shops in your area? You might be able to get Brenspeed to work with you
honestly not that I know of. and I can give them a shot. when I looked real quick on their site, I only saw the tuner for the sn-95 mustangs though
Well if it ran fine before then something happened with the install. Maybe something wasn't connected, broken or anything.

I would run the codes first off.

Secondly I would give the car a good once over visually and check it all out.

What is the timing set at?
What is fp set at?

Now with a freer flowing system you will be able to smell some fumes tho.
Everything is set to factory standards. What I was told is that because the o2 sensors were moved farther away from the motor, they don't get as hot as they need to. This causes the at ratio to be off. Is this the case? One idea my Buddy's shop gave me was a swap from unheated o2s to a heated o2 style. Any thoughts on that?
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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Run your codes. See what pops up. Plus it is free.

The problem is not the location of the O2 sensors.

There are also no magic answers for certain problems as it could be 100 things wrong. Start simple and free then go from there.
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