Hey Guys,

I have a 98 Civic EX with the 1.6L 4 cyl. I just picked up the car and shortly after I got it home, of course, the CEL went on.

The car currently has 145,000 on the odometer. I picked up the car because I needed a cheap gas saver and the guy had just changed the timing belt, fluids, plugs, wires, ignition, and water pump on it. It fires right up, drives fine, but when it just sits at idle, which is around 5-800 rpm, the car rumbles a bit, and sometimes shakes. The man I picked the car up from said that the only thing that he didn't change was the O2 sensor.

I took the car to Autozone to get it tested and the code came back as P0176, which is Fuel Composition Sensor Circuit Malfunction. From what I have been able to gather from the net is that this means the car is running rich due to too much air getting into the motor, and the car overcompensating for the air by using more gas. I honestly just figured this was due to the O2 sensor so I swapped it out and rest the code pulling the 7.5 Back Fuse under the hood. The code came back on while I was on a 2 hour cruise up north. The car only got 22mpg on that trip.

I used a bottle of started fluid and sprayed all of the vacuum lines that I could see and the motor didn't indicate that there was a leak. After that I took it back and got it checked again and the car still brought up code P0176. I'm stumped.

Checking under the hood, the map sensor looks to be kind of tampered with, so I undid the connection and cleaned it up, reset the CEL, and plugged it all back together. After firing the car back up it still has a rough idle, so I feel the light will be back on in no time.

Has anybody else had anything like this happen to them? I've searched this site, and a few others, and haven't been able to find much on this subject, or the P0176 code. If there is something on here or another site and I just missed it please let me know, and I'm sorry for wasting time.

Thanks for the help!

Coastie

 

Does your car have multiple O2 sensors by chance?

 

I just bought the car a week ago today so I haven't visually gotten down and checked but according to everything I've read, yes. It has one before the cat, which is literally right in front of your face on the exhaust manifold as soon as you open the hood, and I've already replaced that one.
There should also be another that is either on the cat, or after the cat.

 

Is the fuel pressure regulator stock? Is the equalizer hose hooked up to it? Excessive fuel pressure will cause a rich condition.

You should remove the spark plugs and look at them. If one is a different color from the rest, that would indicate an issue with that cylinder.

 

I'll check all of that today and get back with y'all tonight when I get off work. Probably around 4-5 central time.

 

I know this below picture is what I'll be looking for but where exactly is it? Is it mounted somewhere on the walls of the engine bay or is it mounted somewhere on the cover above the head by the throttle body? I'm sure I'll find it, I just wanna know exactly where it should be to speed the process so so I can get back to y'all in a good time.

Also, the car didn't come with a manual of any kind, but I have ordered one. (Trying to eliminate the "why are you asking us, look in your manual" speech)

http://images2.carpartsdiscount.com/...76_1580676.jpg

 

Bolted onto the fuel rail.

 

That's what I thought. I'll get back tonight. Thanks!

 

Alright, first off I checked the fuel pressure regulator and that is fine. It is hooked up correctly and seems to be working fine.

On my way home from work the light came back on, so for giggles I pulled back into the Autozone and had them run the code again. This time the code was not P0176. It ran two codes; P0170 and P0172. The man at Autozone told me that these codes still mean that the car is running rich. I have not had time to check those codes on forums yet, I wanted to get this up in around the time I told y'all I would, so I will be checking that here soon.

Anyways, on to the spark plugs. I removed all the plugs, and to me they looked fine. I was going to take a shot of the top of them too but the battery on my phone died. Here is the picture of the plugs after I took them out.



Here is an actual picture of the car itself. I found this on my phone also and figured I'd toss it on here.



The tops of the plugs had some carbon buildup so I cleaned that off, but other then that they didn't look bad.

This is where it got kind of weird for me. I went to put the plugs back in and the two outside plugs went in fine. The two in the center however didn't want to go back in. It was pretty odd to me. I would set the plug in, and it would spin and spin and not go in, but it was caught on something because I had to unscrew it to get it out. It just kind of wobbled like it wasn't in the thread. Either way after messing with it for 10-15 minutes I was able to get the plugs set in place. I've never had this problem before with plugs. Is this normal for 1.6L?

I thought maybe since the plugs were such a pain maybe the other owner didn't have the plugs set right and there was a leak somewhere, so I fired up the car and drove it around the block. It still rough idles and the light is still on.

I'm going to look up those codes and get back with y'all. Just figured I'd get this up.

Thanks guys.

 

Well, knowing that the guy before me changed the timing belt himself before he sold me the car, I'm going to dig into this scenario that this man ran into.

https://www.hondacivicforum.com/foru...ivic-lx-61382/

If y'all can come up with anything else, especially about the spark plug issue I ran into earlier, please let me know. I'll report back tomorrow with my findings.