My car threw a CEL with code 43 today.

[Bad_dude]

My car is pretty well maintain. It's a 90 Accord LX Sedan 4AT. It has 153K miles on it. I have been having bad gas mileage recently and can't find any thing wrong with it. So I ordered a Denso O2 Sensor and just got it yesterday. My original one on the car is NTK. I was going to change it out this weekend. Today while driving home from the market, the CEL went on. Checked it when I got home, 4 long blinks and 3 short ones. Code 43 for "Fuel supply system." I cleared the code to see if it comes back on but I was driving for half an hour after and it has not.
The fuel filter has been changed twice since I got the car and that was 4 years ago with 122K miles on it. The fuel pump is fine as there's nothing wrong with the car acceleration and timing is perfect idle at 750 when warm.
A lot of the CB7 owner replaced fuel pumps and fuel filters, fuel regulators but what seem to fix it is the O2 sensor. This car only has one so no guessing on which one. What else could this be if replacing the O2 sensor won't fix it?

Thanks.

[cloudasc]

Its always the o2 sensor that causes a code 43. Its also one hell of a bugger to get show up, I had to drive about 2.5-3 hours straight before it finally gave me a dam code, all the while it was intermittently stuttering at low rpms, but I could WOT, and it would "break free" of the stutter/bogging.

[Bad_dude]

It's funny how I was going to replace it any way and it decides to throw the code the day before.
How about cleaning the old one?
http://www.doityourself.com/stry/how...-oxygen-sensor

[deevergote]

43 is an o2 sensor code. When you change the sensor and reset the ECU, it will go away. To reset the ECU, pull the "radio/backup" fuse for 15 minutes, and/or disconnect the battery for 15 minutes. Drive around normally for a few miles to allow the ECU to recalibrate.

[Bad_dude]

After you guys replaced your sensor, did you notice any improvement on the fuel mileage? I went from 26 to now low 20. And this was why I decided to buy a new one in the first place.

[deevergote]

Replacing a faulty o2 sensor will improve fuel mileage, yes. The purpose of the sensor is to tell the ECU how much fuel needs to be sent to the engine (to put it simply...) When the o2 sensor fails, the ECU doesn't know what to do, so it sends more fuel than necessary, since more fuel is less likely to do damage than less fuel.

[Bad_dude]

Thanks guys. I am going to get some coffee then will take the heatshield off. Then spray the WD40 on the old sensor and while waiting I am going to paint that nasty shield black.

[Bad_dude]

A nice guy over at Eric the Car Guy gave me this link.
http://ww2.justanswer.com/uploads/th...054_dtc_43.pdf

[Bad_dude]

I replaced the O2 sensor and can feel the difference in the car already. Much more responsive. The car also shift a little earlier if I don't gun the pedal. Before it usually shift at 3000rpm and now it shifts as early as 2000rpm.
But my 4th gear bogging is still there. Every time it shifts into 4th gear on the freeway when I floor it, it bogs down and I have to let go of the pedal slightly to regain speed. You can feel and see the bogging in the tach meter. If I let my foot off slowly from the pedal, the car regain and you see the tach shoots right up and takes off really fast.
Oh, I did not paint my heat shield as I could not get it off. The AC freon pipe in the front was preventing it from coming off and I didn't want to bend that soft tube and break it so I'll have no AC in SoCal is hell. Maybe some one with the same car and has taken it off before could give me some pointers.

Thanks.

[wed3k]

might sound like a converter lockup issue.

[Bad_dude]

might sound like a converter lockup issue.

You mean my 4th gear bog down? Would you explain it please?

Thanks.

[Oreellyfool]

So i have been fighting with the 43 as well for the past couple months. I finally figured it out. (And I did try 4 different O2 sensors)

So I had the bogging as well. My MPG went down to around 20mpg and I was running very rich.

What my problem was, was the fuel pressure regulator. I ended up grabbing one at a JY just to test it and it fixed it. I tried just about everything in the manual.

You should try checking your fuel pressure on the rail with a gauge and see if it is in spec. Easy way to tell if your FPR is bad.

[deevergote]

Wow, a Code 43 that really DOES have to do with he fuel supply system? That's a first! (I don't mean that sarcastically... in about 30 instances I've seen on this forum, maybe more, it has ALWAYS been the o2 sensor.)

[Bad_dude]

So i have been fighting with the 43 as well for the past couple months. I finally figured it out. (And I did try 4 different O2 sensors)

So I had the bogging as well. My MPG went down to around 20mpg and I was running very rich.

What my problem was, was the fuel pressure regulator. I ended up grabbing one at a JY just to test it and it fixed it. I tried just about everything in the manual.

You should try checking your fuel pressure on the rail with a gauge and see if it is in spec. Easy way to tell if your FPR is bad.

So how did you test your fuel regulator?
Thanks.

[deevergote]

Test your fuel pressure. If it's not where it should be, then your regulator is probably bad.