PDA

View Full Version : 4.0L HO running rich


Mudderoy
10-26-2009, 02:39 PM
Okay I've been fighting a mpg issue for a few years now. I was down around 10 mpg and now I can get up to 14, but usually hover around 12.5 to 13.5.

I purchased an OBD II scanner about a year ago and along with a laptop I can collect data on the engine as I am driving it down the road.

My upstream O2 sensor data was acting as expected, however instead of swinging between .25 and .9 volts it stays between .5 and .75 volts while driving down the road at 60 mph steady.

This would indicate a rich situation.

Why would I be running rich? I have heard a leaky injector. Should I just replace all the injectors and see if that fixes it? Remember I am getting the data from the ECU so the ECU should know that the O2 sensor is reporting a rich situation.
cheap jeep
10-26-2009, 05:34 PM
If your fuel pressure regulator is bad it will draw fuel right into the intake. To check it, pull the vacuum off at the intake, if it's wet it's bad. I have done these on Chevys and Fords,but not my Jeep.
muddeprived
10-26-2009, 05:50 PM
If your fuel pressure regulator is bad it will draw fuel right into the intake. To check it, pull the vacuum off at the intake, if it's wet it's bad. I have done these on Chevys and Fords,but not my Jeep.

Where is the vaccuum located on the intake?
cheap jeep
10-26-2009, 08:09 PM
The fuel pressure regulator is on the fuel rail. It has a small vacuum line that goes to the intake manifold. On my 92 it's on the top, close to the front by no.1 cylinder. hope this helps.
BlueXJ
10-26-2009, 11:19 PM
What readings are the downstream O2 giving you Muddy? I think the ECU averages those two readings on OBDII Jeeps.
Mudderoy
10-26-2009, 11:40 PM
My PC is down right now and all that information is on it. Motherboard coming in Wed or Thur. I was reading about the fuel pressure regulator. No such luck about it being in the engine bay, try on top of the fuel tank. At least that is what I read. :oS
cheap jeep
10-27-2009, 08:38 AM
On my 92 XJ the fuel pressure regulator is on the fuel rail, along with the injectors. I don't know about a newer one. If you go to a parts store( Autozone) they can bring out a new one so you know what it looks like,also if yours is located differently than mine, they can pull up a procedure program to show how to change it usually. That's what I do when I work on something I'm not used to. Sorry if I misled you.
Mudderoy
10-27-2009, 09:26 AM
On my 92 XJ the fuel pressure regulator is on the fuel rail, along with the injectors. I don't know about a newer one. If you go to a parts store( Autozone) they can bring out a new one so you know what it looks like,also if yours is located differently than mine, they can pull up a procedure program to show how to change it usually. That's what I do when I work on something I'm not used to. Sorry if I misled you.

No, no problem. It still good information no matter where the regulator is located. ;)
alwaysxj
10-27-2009, 12:57 PM
as far as i know i it is on the tank. but what do i know i'm from utah.
Mudderoy
10-27-2009, 01:14 PM
as far as i know i it is on the tank. but what do i know i'm from utah.

Good point! :P :smiley-laughing021:
alwaysxj
10-27-2009, 02:20 PM
Good point! :P :smiley-laughing021:

thought you would like that.:smiley-gen165:
Mudderoy
10-27-2009, 02:22 PM
thought you would like that.:smiley-gen165:

Our neighbors are from Utah, and they are Mormons, go figure. :smiley-laughing021:

I think they drive to Utah every year.