97 V6 with P0172 code

[Astro Bob]

97 TBird, with 3.8L V6 and auto trans. just over 100,000 miles. This just started. I got an engine service light, and my reader said P0172 (bank one rich). I noted the code in the back of the reader manual and cleared it to kill that very bright light, and to see if it repeated. Several months later, I got the same code, but the car ran fine, so I cleared it again. Recently, the car has a problem at or near idle. I get a vibration and the idle RPM seems to drop a little. If I have any load on the engine, such as AC or the rear defogger, I can feel the engine lug a bit when in gear. When cold, I sometimes get a stumble when hitting the gas to move into street traffic, but just a stumble.

Then it goes away, the engine smooths. I've kept a mileage log, and my combined mileage is about 19 MPG, and has not changed since this problem started. The car has never stalled due to this problem. The engine management system is doing a great job, but I'd like to fix this. I just bought a set of platinum plugs and a tube of dielectric ignition grease. I'm considering new spark wires also, just because of the age of the car. I've read about the MAF sensor, that being dirty can sometimes cause that code to pop up, but most of the posts and bulletins don't mention a driveability problem unless the MAF is really filthy, or unplugged.

Is bank number one on the driver's side, or the passenger's side of the engine? I'm going to change all six plugs, but I'd like to be sure which side is which. The OBD2 code listing is not helpful.

I just received a copy of the original Ford shop manual (very confusing at first), and I've got a few aftermarket manuals, but I just started digging into them about this. ( I really like the manual for my 83 Nissan 280ZX Turbo much better than this Ford manual. Much easier to understand and use!)

Any suggestions? All comments and help are appreciated. Anything else I should be doing to the car at 100,000 miles, maintenance-wise?

I really like my Laser Red car, and want it to run as good as it looks again. Thanks!

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[007_SuperCoupe]

I don't know too much about the OBD2 computer codes as my SC is still under the EEC IV system. What I do know, however, is that if you have either a rich or lean code and you have NOT modified your car (meaning injectors, tune, supercharger, etc) then 95% of the time, that code means that the O2 sensor(s) are bad.

At 100k, my recommendation would be to do a complete tune-up. Plugs, wires, O2 sensors, inspect belt and hoses and replace as needed, air filter, fuel filter, tranny flush, differential flush, etc. Also, I recommend a can of BG44k in your fuel. This is a once-a-year treatment (costs $20-$25) that cleans everything from the fuel pump, filter, injectors, exhaust valves and port and O2 sensors. Assuming that you have never used it before, a couple treatments may be required to fully clean your fuel system. Don't use other cleaners like STP, etc as they may clean out the injectors, but create a significant amount of carbon build-up on the exhaust components (valves, runners and O2 sensors). The BG44k is best used if you will be travelling a long distance. It works best when the engine is at 2k rpm or higher for hours at a time. In and around driving in town does not allow the BG44k to function to its full potential.

I hope this helps. Let me know if you have any questions about what I stated. Good luck!