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Fault code: 5-1-2 "short term fuel mix too rich" 850 1994

Check engine light comes on at start and stays on. Checked fault codes and got 5-1-2 " short term fuel mix too rich" Any suggestions. Have just swiched from a 1984 244GLE to the 1994 850 and the 5cyl is new to me.

M








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Re: Fault code: 5-1-2 "short term fuel mix too rich" 850 1994

The most common cause for tihs code is an improperly malfunctioning front O2 sensor. However, there could be a number of other causes. For example, vacuum leaks, dirty air filter, improperly operating ECT, etc.

The first thing I would do is work on the O2 sensor. Often, the sensor is so funked up with crud, that it doesn't operate properly. To clean it, do the following:

- unscrew sensor from exhaust line (if it is the original, don't be surprised if it is basically seized by being cross threaded and/or overtorqued, in this case, penetrant won't help much, but a torch will)

- heat the node of the sensor with a torch until it glows orange, and keep it this hot for 2-3 minutes

- wait till the sensor is cool enough so that when you spray the non-chlorinated brake cleaner on it, that it doesn't sizzle

- spray non-chlorinated brake cleaner on the sensor (at this point, you should see quite a bit of crud being washed away by the brake cleaner, considering you just burned off 95%+ of the contaminants, that's a heck of a lot of crud)

- wait for the brake cleaner to evaporate

- heat the node again with the torch until it glows orange again, for 2-3 minutes

- you may also want to open up one of the slits in the node a little (this often helps with rich and lean problems)

I used to pull front O2 sensor codes every couple months, then weeks, then almost everyday. At that point, I was full and ready to put in a new O2 sensor. But, an engineering friend of mine explained why it was failing, and how I could fix it. So I did, and I have just explained how to do it.

Even if you find that it was an vacuum leak or a clogged air filter or a faulty ECT, you will probably want to clean off the sensor, as running rich will foul the sensor very quickly.








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Re: Fault code: 5-1-2 "short term fuel mix too rich" 850 1994

OK Guys,

Tried the airfilter (no change) figures it wouldn't be the cheap way out...

Went to buy the O2 Sensor, but there were two types..One for an 850 with an air pump $157 and one for an 850 Without an air pump $144.....

Question... Whats an Air pump and how do I tell if I have one???

Marco








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Re: Fault code: 5-1-2 "short term fuel mix too rich" 850 1994

Sin, I've never mucked with the O2 sensors (knock wood) but

I do recall some posts here indicating that wiring problems

to the sensors were common. This might be something to check

out first if you don't want to take a torch to the exhaust :)








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Re: Fault code: 5-1-2 "short term fuel mix too rich" 850 1994

I believe the wiring problems were regarding wiring of universal O2 sensors.

Hey, besides a 5 lb mallet and kroil penetrant oil, I think the torch is my best tool :)








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Re: Fault code: 5-1-2 "short term fuel mix too rich" 850 1994

Marco wrote:

> Check engine light comes on at start and stays on. Checked fault

> codes and got 5-1-2 " short term fuel mix too rich" Any

> suggestions. Have just swiched from a 1984 244GLE to the 1994 850 and

> the 5cyl is new to me.

When I got that code it also came with the front O2 sensor bad code. Replacing the O2 sensor cured both.

Bill Matthews

Hockessin DE

94 855T

95 854GLT

73 1800ES

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