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Discussion Starter #1 (Edited)
'95 LX 4.6 w/237K miles.

About 250 miles into a 500 mile trip today and the car starts running rough. Stumbling on light acceleration. I hate having to ride the right lane on the highway. Had my code reader in the console so I plugged it in. Some high fuel trim numbers but I didn't see anything obviously wrong. About fifty miles later the check engine light finally came on. P0171. Not that again. Shouda brought the MAF sensor cleaner. Checked codes again about 50 miles later, imagine my excitement when I saw Enhanced DTC found! P1130 and P1131. Car would run respectable in the 70-75 MPH, 2,000-2,500 RPM range, but when encountering traffic and trying to accelerate in third gear (30-60 MPH) it stumbles. And really runs scary in stop and go traffic, so much that I frequently shift to neutral. Accelerating, feathering it around 2,000 RPM trying to find a throttle position that it likes, it will either drop to 1,800 RPM and stumble, or "catch" and rise to 2,200 RPM and accelerate nicely. Was still able to blow off some slow pokes hogging the left lane, although in addition to leaving them in the dust I also left them in the smoke. So anyway completed the trip and checked the tailpipes to find substantial soot. Did some research on what needs fixing. I'll give the MAF sensor a liberal dose of MAF sensor cleaner tomorrow. Probably won't help. Then when I get home check the plugs for indication of a failing/failed fuel injector and repair/replace as needed. And check if the electrical connection on the Bank 1 upstream O2 sensor looks okay and if I need to order up a new Motorcraft O2 sensor to replace the original one.

Will report on the progress after I check a few things.
 

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Discussion Starter #2
Deluged the MAF sensor with CRC MAF sensor cleaner and it's running good now. Went to clear the codes and found a P0402 as well. ha-ha, that one again. Still have 500 miles to drive home but I think if I keep my right foot out of the fuel injectors it will run fine. When I get home I can take a deeper look at it.
 

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Discussion Starter #3
Drove 500 miles today without incident. Shoulda brought the MAF cleaner (thought to bring it a couple days before but then didn't remember to take it), coulda saved myself some anxiety. Only P0402 code came back. Haven't done any diagnosis yet, will report if I find anything noteworthy.
 

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Interesting codes.... they do suggest that the O2 readings aren't matching up with the other readings like MAF.

I'm glad it was the MAF sensor. The ignition and fuel system on these can yield so many random symptoms.
 

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I used to get the P0402 code on my 95, and when I did, the gas mileage usually went up, with no ill effects.

There is no way that cleaning a MAF that is already 99.99% clean will make a difference, ie: needing to always have the cleaner with you.

The only time I had an issue with a dirty MAF was when the car pinged at WOT, and the MAF had 150k miles on it w/o being cleaned.

Hopefully some new Motorcraft o2's will clear it right up.

Al
 

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Discussion Starter #6
Was running great on the New Jersey Turnpike, I was passing everything. Started running crappy on the Garden State Parkway. Do know that the problem went away after I removed the MAF sensor, cleaned and reinstalled. I didn't touch anything else. Checked the spark plugs after I got home, nothing noteworthy. O2 sensor codes have not returned and I have not done anything to the O2 sensors.
 

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Discussion Starter #7
Update: replaced the left bank O2 sensors last week, made a world of difference.

Last month on a long trip the P1131 came back. Running bad but not nearly as crappy as when it happened last year. Figured it was time to finally take the sage advice of installing new O2 sensors. New left side sensors makes it run so much better at low RPM. Just ordered up another pair to do the right side.

Side note, the P0402 has been persistent. Since it's from excessive EGR flow, I figured either EGR is clogged open or the PCM is telling the EVR for more vacuum to the EGR when it shouldn't be. I figured eventually I'd be cleaning and reinstalling the EGR valve that I removed and replaced early last year. So anyway on that 1,000 mile trip last month, I reset the MIL for P0402 three or four times during the first half. But then the code did not come back during the return trip. So as far as I'm concerned, it's good to go for now.
 

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Update: replaced the left bank O2 sensors last week, made a world of difference.

Last month on a long trip the P1131 came back. Running bad but not nearly as crappy as when it happened last year. Figured it was time to finally take the sage advice of installing new O2 sensors. New left side sensors makes it run so much better at low RPM. Just ordered up another pair to do the right side.

Side note, the P0402 has been persistent. Since it's from excessive EGR flow, I figured either EGR is clogged open or the PCM is telling the EVR for more vacuum to the EGR when it shouldn't be. I figured eventually I'd be cleaning and reinstalling the EGR valve that I removed and replaced early last year. So anyway on that 1,000 mile trip last month, I reset the MIL for P0402 three or four times during the first half. But then the code did not come back during the return trip. So as far as I'm concerned, it's good to go for now.
I used to be a factory ford tech at a ford dealership, and most of the time if you get a po402 insufficient egr flow, it's the safe sensor that causes this code,hope this helps someone out there, GOD bless my T bird brothers and sisters
 

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I used to be a factory ford tech at a ford dealership, and most of the time if you get a po402 insufficient egr flow, it's the safe sensor that causes this code,hope this helps someone out there, GOD bless my T bird brothers and sisters
Well, on a 94/95, it's because the EGR channels are completely clogged. They clog from bad valve stem seals.

Trying to jump start your post count in the same 2 yr old thread? Might want to make an introductory thread.

Al
 

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Discussion Starter #10
On my 95, P0402 means excessive EGR flow.

Hadn't driven it for a couple weeks, was running rough at first and my old friend P0402 came back. He couldn't stay long, used to visit all the time.
 
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