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2004 Mustang GT running lean, poor idle, loss of power

20545 Views 12 Replies 3 Participants Last post by  AdmiralSavage
Hello everyone. I'm new here so bare with me but I will be extremely grateful for any help I receive.

I got my 2004 GT about a month ago and it has roughly 190,000 miles on it. It started with code 0301 (misfire on cylinder 1) so I replaced the coil and plug, problem solved.

Shortly after it threw code p2195 (Bank 1 Sensor 1 Stuck/lean) and started idling pretty rough at stops. After reading a bunch of forms I was pretty convinced the rough idle was a misfire so I replaced all the coils and plugs and had no results. A family friend replaced both sensors on bank 1 and the code went away and the car was running normal, (no rough idle).

A few hours after I got rid of code 2195, code 401 pops up (egr insufficient flow) and the rough idle comes back. What I found was a brittle egr vacuum hose taped together so I replaced it with a soft line, deleted the code, and it hasn't come back. A significant amount of carbon did fall out when I removed the line from the egr diaphram.

I went awhile without any check engine lights but recently I started throwing code 2270 (bank 1 sensor 2 stuck lean). This is one of the sensors that has been replaced.

Right now the car's idle has awful shaking and surging that gets worse with the a/c on. For the most part I don't feel it when the car starts rolling. I do not know what type of o2 sensors were put on the car but the family friend who builds drag racing engines and is a mechanic very familiar with fords said they were "racing o2 sensors" and they would work fine. So I didn't second guess it but probably should have figured out what brand they were now knowing that if they are bosch sensors my car wont like them.

If these were bosch o2 sensors would it cause my car to run this poorly?

Here's a list of what I've tried.

- new coils and plugs
- cleaned maf sensor
- replaced fuel filter
- checked for vac leaks with carb cleaner (I couldn't find anything)
- ran injector cleaner
- replaced the o2 sensors on bank 1

The car definitely had heavy modifications on it before but it looks like the previous owner put everything back to stock accept for the cold air intake and it is h piped. There is an extra pulley with nothing on it that looks like went to some kind of forced induction.

I'm stumped.

I don't want to bore everyone with too much writing so if you are missing any information that would be useful let me know!
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Im having almost the same problems as you, i even put in a stock 4.6l engine since the other was heavily modified. I have replaced pretty much every sensor on the car. The car will not hold an idle and smells rich, my fuel trims looked really high. I was getting a code for bank 2 lean, p1151 and also p1401 for the dpfe sensor. I checked for vacuum leaks i could not find any after spraying carb cleaner all over the engine bay. Ive replaced o2 sensors also, the problem persists. The car will idle around 950rpm without ac. When i turn the ac on it will start to idle at 700 immediately. Sometimes the idle will surge up and down on its owm and stall out the car. Only thing i can think of is a failed pcm???
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