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post #1 of 8 (permalink) Old 10-08-2011, 09:57 PM Thread Starter
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Keep getting lean codes

Basic info: 1997 3.8 Thunderbird, 190,000 miles
I got this car a month or 2 ago. It's in good shape, especially considering the mileage, but it needs a lot of attention to little problems. It kept throwing codes for lean on both banks (don't remember the numbers), felt like it was choking out under harder acceleration, was down on power across the board, plus there was a weird chugging issue between 1500-2000 rpms that would vary in intensity. I changed out the air and fuel filters, cleaned the MAF (the wires were covered in a fine dust), put in new plugs (Motorcraft OE platinums) and wires (Borg Warner), and changed the EGR valve. The chugging is reduced down to a slight stutter occasionally, the lean codes stayed away, the choking feeling is gone, and power is up from idle to redline.

This morning the lean codes popped back up. They stayed away for a few weeks, none of the other problems have returned, and it's still running great.

What the...

I'm going to clean the MAF again just for kicks. If the codes keep coming back, I'm thinking the fuel pressure regulator is next to be replaced. I don't want to start replacing parts and hope it works though. The stutter appears to be the trans - I'm going to change the fluid and do a Jmod while it's cracked open - so I don't think they are related but not totally sure.

Is there something I'm overlooking here or a common problem with these cars I'm unaware of? Anyone got any ideas?

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post #2 of 8 (permalink) Old 10-09-2011, 05:16 AM
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What are the codes? Original O2 sensors?

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post #3 of 8 (permalink) Old 10-09-2011, 06:18 AM Thread Starter
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I cleared them before I wrote the numbers down. There were 2, "Lean left bank" and "Lean right bank".

I'm pretty sure it's the original O2 sensors but I'll check the paperwork I've got to be sure. Is there a way to find out if they are the problem instead of just crossing my fingers and hoping?

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post #4 of 8 (permalink) Old 10-09-2011, 03:00 PM
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The first thing to check would be vacuum leaks anywhere after the MAF. If the o2s are original, chances are that by 190k, they are getting lazy. You check them by hooking up a scanner and watching the data after they warm up. With an engine not misfiring and with no vacuum leaks, the data will switch from like 100mV to 800mV constantly. You may also just have a clogged fuel filter.

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post #5 of 8 (permalink) Old 10-09-2011, 04:27 PM Thread Starter
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That's what I am looking for. I just want to be sure instead of throwing money at the car and hoping I catch the right thing.

Just changed the fuel filter about 3 weeks ago, it may be a clogged sock at the pump though. A clogged filter or sock would be a constant restriction, not something that comes and goes, right?

If there is a vacuum leak, I haven't found it. I'll check again when I wash the car in a minute.

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post #6 of 8 (permalink) Old 10-09-2011, 05:24 PM
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yea most likely

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post #7 of 8 (permalink) Old 10-09-2011, 11:32 PM
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I have never seen a sock that caused any problems on a Ford. There are TSBs for newer GM cars though that call for a different fuel pump sock. I would do a fuel volume and pressure test before doing anything inside the gas tank. Gas tanks suck too much to drop, especially when full.

-Rob
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post #8 of 8 (permalink) Old 10-10-2011, 12:05 AM Thread Starter
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The O2 sensors are original and didn't see any vacuum leaks. Drove around for awhile today without the codes popping back up. Going to test the O2 sensors to be sure but that's probably going to be it. If that isn't it, I'll check the pressure and go from there. Thanks guys.

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