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At 122,000, the service engine soon light came on. I dropped in to my local shop who just did an excellent job on repairing my AC. He read the code, and came up with the PO172, running rich, right bank. He said come back, leave the car for a couple hours in order to pinpoint the problem. Two hours to diagnose this seems excessive. How many things could be the cause?

The car runs like new. I doubt a vacuum leak, but suspect the culprit to be in the exhaust system. Any thoughts appreciated. In the mean time, I'm in the market for a code reader with the ability to show me what to replace.

Thanks one and all.
 

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Most likely, is bad o2 sensors.

Buy two new ones, for the front position, and swap the front ones to the rear position.

That may not be possible if they're original, they're keyed.

That starts the diagnostic process; get TDK sensors from RA, not Bosch.
 

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Most likely, is bad o2 sensors.

Buy two new ones, for the front position, and swap the front ones to the rear position.

That may not be possible if they're original, they're keyed.

That starts the diagnostic process; get TDK sensors from RA, not Bosch.
Thank you. I have two fairly new rear sensors from my totaled '95. I will report progress. In the meanwhile, a short video explaining fuel trim. It turned the light on in my head.

Also planning on cleaning the MAF sensor. Previous owner installed the dreaded K&N filter which I will replace with paper.
 

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Anything upstream of the intake manifold will throw a code on both banks .. if you are getting a code only on one bank its more likely a bad o2 or vacuum / exhaust leak on one side of the engine.

I would like to know where I can find a code reader that tells you what to replace also. Its a tool used for diagnostics, it doesn't exactly tell you what to replace unless you know what to look for or have a comparison with a known good working part / values. A high end scanner will run you upwards of $10k but you can monitor the actual fuel trims .. if you are borderline on one side and over threshold on the other side, I would be more inclined to suspect a vacuum leak upstream, but if only one bank is way out of value it would me more in line with my previous statement. Ford has a pretty high threshold for fuel trim before it throws the code, somewhere around 30% of additional fuel on the long term trim before it throws the code.
 

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I would say; if you plan to keep your car, buy a used Xcal2 on ebay, that's unlocked. The unlocked part is important.

It will allow you to datalog your car to a laptop, which are dirt cheap these days.

You can log any problems you may ever have, and it's also coot if you change stuff, you can use it to tune your car.

Vacuum leaks, Maf going bad, clogged cats; all this **** happens to 20 yo cars.

There are upgrades to all of it, but an xcal2 and a tune are part of that.

Start with the easy stuff, o2's are only slated to last 5 years, from the design specs.
 

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I would say; if you plan to keep your car, buy a used Xcal2 on ebay, that's unlocked. The unlocked part is important.
I haven't seen an X2 on ebay since I owned my old cougar few years ago, but you can still find fairly priced X3 models and of course there's X4 for days.

I'd wager that it's an O2 sensor that hasn't quite failed but is on its way there, or possibly an injector leaking down or otherwise flowing too much... I had a couple bad injectors with the last batch I had on my 'bird throwing rich codes, so I picked up some genuine Ford Racing units and *poof* problem solved.
 

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IDK what year car this is, but the 94-95 4.6's are well known for hanging an injector open; it's the eec, and can be diagnosed with an injector light.
 

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IDK what year car this is, but the 94-95 4.6's are well known for hanging an injector open; it's the eec, and can be diagnosed with an injector light.
Or the huge cloud of white smoke that pours out of the exhaust pipe.
 

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Discussion Starter #9

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NTK; I've been on a recording kick lately. Sorry. :)
 

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