I know this means the mixture is rich and the carb needs adjusted on a carbed truck,but what about on a truck with efi? At idle standing outside the truck,the exhaust smells rich like unburned fuel. this is for my 95 f150 5.0. with long tube headers. it smells this way when the engine is cold or warmed up. there are no codes and the fuel pressure is within spec. I am not sure what else to check. if it were the o2 sensor,wouldn't the computer be throwing a code saying it is bad? thanks!!

 

When you say fuel pressure was in spec what were your readings?

 

Does the FPR leak? Start the motor and remove the vacuum line, if you see any fuel it's busted and must be replaced.

Where is the O2 sensor installed?

 

Paul,not sure if the FPR leaks or not,i will try to check tomorrow. the o2 sensor is located in the collector after the header on the passenger's side.

 

32 psi was the fuel pressure at idle,and only moved a couple psi when the rpm was raised. I just checked to see if there was fuel in the fpr line,and there wasn't,so I am thinking it is ok. also fuel pressure was 40 psi when the fpr vacuum line was disconnected. i know the fuel pressure is supposed to be higher with the vac line disconnected,but is 40 psi too high?

 

I don't know a lot about this but here are some thoughts...

If the o2 sensor is only located on one side of the exhaust, maybe the sensor is only reading half of the emissions. These motors are bank fired aren't they? I believe that the stock exhaust systems usually locate the o2 in a connecting pipe on the y-pipe.

Also, if you have long tube headers, what did you do with the egr system?

 

I have been running longtubes for years now and had no problems passing emissions with the O2 sensor in the passenger side header. Have you pulled the codes just to see if anything is stored?

 

yes,i pulled the codes. the only code in the computer is code 181,which i posted about a couple weeks ago. according to my book,code 181 means o2 sensor unable to switch/lean during part throttle. if this is the case,why does it smell rich at idle?

 

According to Fordfuelinjection.com code 181 is " Right side still lean, at richest adaptive limit, during part throttle."
That means the O2 sensor is indicating A/F ratio is lean even though the computer has added as much fuel as it can. But the engine is actually running rich.. strong fuel smell in exhaust, so the O2 sensor is giving the computer bad info and most likely needs to be replaced. The only other way this could happen is if the air diverter valves were stuck and all the air from the air pump was being dumped into the heads or exhaust upstream of the O2 sensor.

 

well,i was thinking o2 sensor,but just trying to be sure. and I know it isn't the air pump because it is deleted.

 

Hey, how bout that? Most of the vacuum lines under my hood were cracked and brittle, so I removed them all and replaced only the critical ones like for the FPR. Then as I always do, I removed all the emission controls- less parts means more working room and less problems. I've been meaning to plug the lines that come from the heads that used to go to the air pump, but man I simply didn't realize leaving them open like I did would allow them to draw air in and make the o2 sensor read lean. No wonder I'm down to 6 MPG and my exhaust smells rich. I thought I left a vacuum port uncapped or something.

Sure am glad I read this thread.