Probs with "Upstream air sensor"

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Probs with "Upstream air sensor"

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Probs with "Upstream air sensor" - 5/6/2005 4:46:33 PM

kiltwearinfool

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Joined: 5/6/2005
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Hello y'all, I have a '97 4-door 2.0 5-speed with about 120K miles. With regular maintenance it's been a good little commuter car for me for about 5 years now, but it recently developed a problem that's proving difficult to diagnose.

About 3 weeks ago while I was out of town the "Service Engine Soon" light came on. I took it into a Midas shop to see if they could give me an idea of what was wrong. The fella told me OK, but there were some issues he could not fix, only a dealer could.

He plugged in his OBD reader & got the code. Unfortunately I did not have him write it down, but he told me that the code translated into a "Problem with the upstream air sensor" and that the car was running lean.

I had been experiencing some minor idling problems (rough idle after warming up for 12-15 minutes), but nothing major, no stalls. The Midas man told me this was a problem for the dealer.

While I took his word, I wanted to check things with my local independent mechanic. While not a Ford specialist, he does come recommended by a friend. He plugged in his own OBD reader, got the same message that the car was running lean. However, he was not able to localize the problem. He instead felt there was a leak in the intake system somewhere, and proceeded to "smoke" the car. Apparently this is an old-school method of traking leaks whereby a smoke generator is hooked up to the intake & the engine is observed for any leaking smoke.

So my local guy couldn't find anything. He reset the light and sent me on my way.

Meanwhile, I have been thinking of all the things I might be able to replace in effort of fixing the problem. I own motorcycles and bicycles, and do quite a bit of my own labor (from changing oil and brake pads all the way to rebuilding clutches and gearboxes on old Triumphs).

I found an Upstream air sensor on rockauto.com, and I'm wondering how difficult it is to replace. My Haynes manual does not list it, but I know it's somewhere on the intake/exhaust.

Anyone have any tips? Thanks in advance.

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RE: Probs with "Upstream air sensor" - 5/6/2005 6:55:13 PM

solo_one

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Joined: 4/17/2005
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I dont know how well the smoke method works, but I always found vacuum leaks by spraying starting fluid or carb cleaner around the intake and any vacuum hoses. Spray an area, wait a few seconds, and if the idle increases, you've found your leak. Good luck!

(in reply to kiltwearinfool)

Post #: 2

RE: Probs with "Upstream air sensor" - 5/8/2005 12:54:47 PM

truckpuller

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Joined: 2/26/2005
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Mass air flow sensor maybe which is usally located in the air intake duct before the throttle plate.
Oxygen sensor is located in the exhaust pipes .

Good Luck