Exhaust smells rich and decreased mpg

[Kermit]

99 4.6 xlt 191k mi...Just like it says, today leaving a clients house idling for a bit before I left I noticed the exhaust smelled rather rich compared to how it usually smells. No smoke tho, and it was the second trip out for the day. Oil change about 3 weeks ago, refilled with penzoil 10w30 non synthetic for higher mileage vehicles.

Also I noticed I'm getting about 10+ miles less per quarter tank of gas. I was averaging about 100 miles per quarter tank, now I get around 86ish under the same driving conditions, except obviously a bit colder out.

Oxygen sensor? Thoughts?

 

[Bedrck47]

How many MPG are you getting
Have you had the codes read?
I would think if it was a O2 sensor you would be getting a CEL.
Have you ever cleaned the exhaust ports thru the throttle body.
Check the hoses on the DPFE sensor for tightness or any signs of cracking

 

[lve2wheel]

roxy1225 How do you clean the exhaust ports through the throttle body? mine could probably definitly use that.

 

[Bedrck47]

The 5.4 doesn't seem to get fouled as bad as the 4.6
The 5.4 has only one large port. The 4.6 has two smaller ports and that is why they tend to clog
There is a very good video on youtube on this subject
Your best bet is to remove the throttle body and spray the ports with TB cleaner

My 99 with the 4.6 was clogged solid
The current 01 has the 5.4 and really only needed a good spraying

if I can find the video I'll post the link

 

[Bedrck47]

go to youtube and search this

P0401 code ford Throttle body EGR port cleaning 4.6 Ford Expedition part 1 of 5

 

[1997SCEBFEX]

02 sensors/cats, crazy vacuum?

Let us know what you find as resolve.

Best,
PanHandler.

 

[01yellerCobra]

I'd say O2 sensors too. Especially if they're original. They can diminish without throwing a code. I had that issue on my Cobra. One of the sensors was still switching so the computer thought it was good, but it wasn't using the full range.

 

[FordandPolaris]

Agreed. My O2 sensors are stuck beyond belief so I have just been dealing with the bad smell and gas mileage. When it gets cold here I drop to about 7mpg's on 87 octane, but if I switch to 89, it goes back up to the normal 12-14mpg's. I think it's the particular winter blend at the Brand gas station I use, but it's worth a shot on the next fill up if you are waiting on the O2's

 

[Kermit]

Thanks for all the replies. We did find one of the o2 sensors with a loose connection, fixed that, and unhooked the battery to clear the check engine light. Light came back on ... Looks like a trip to advanced for a code check.

The mileage, Was averaging 16ish miles a gallon. I'm at a half tank and should have close to 200 miles on my trip counter, I'm in the 160s running 87 octane. High ethanol content up in my area but a station is offering an ethanol free 89 octane for 10¢ more a gallon. Worth it ?

 

[Bedrck47]

when you get the codes read, post them

 

[Kermit]

Will do that

 

[FordandPolaris]

Thanks for all the replies. We did find one of the o2 sensors with a loose connection, fixed that, and unhooked the battery to clear the check engine light. Light came back on ... Looks like a trip to advanced for a code check.

The mileage, Was averaging 16ish miles a gallon. I'm at a half tank and should have close to 200 miles on my trip counter, I'm in the 160s running 87 octane. High ethanol content up in my area but a station is offering an ethanol free 89 octane for 10¢ more a gallon. Worth it ?

I would personally. Just based on what I have read in the past, ethanol can gum up motors. And at 10 cents per gallon in a 30 gallon tank (what my truck has), you are paying an extra 3 bucks. Buy roxy is right, post the codes, could be something completely different.

 

[Kermit]

Just checked the octane rating on the ethanol free, hubby thought it was 89 but it's the super, 91 octane, is that to rich for my motor? Manual says use 87 octane

 

[01yellerCobra]

There's no benefit to running the 91 if you're not tuned for it. It won't kill your mileage though.

 

[Kermit]

Yeah my motor isn't tuned to anything cept factory specs.

Checked the code today... p0401... Improper air/fuel mixture is what the reader said, with that code.

 

[Kermit]

There's no benefit to running the 91 if you're not tuned for it. It won't kill your mileage though.

Care to elaborate on that won't kill your mileage part. I should get better mileage shouldn't I?

 

[Bedrck47]

Have you cleaned the exhaust ports thru the throttle body

 

[01yellerCobra]

Care to elaborate on that won't kill your mileage part. I should get better mileage shouldn't I?

The engine doesn't know what octane you're running. It's only going to command whatever timing is programmed in the ECU. The only way the 91 will give increased MPG is if you've been running bad 87 and the computer has been retarding timing to compensate. Then switching to the 91 would allow full programmed timing.

 

[Bedrck47]

P0401 - EGR Flow Insufficient Detected

The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum.

Vacuum supply
EGR valve stuck closed
EGR valve leaks vacuum
EGR flow path restricted
EGRVR circuit shorted to PWR
VREF open to DPF EGR sensor
DPF EGR sensor downstream hose off or plugged
EGRVR circuit open to PCM
VPWR open to EGRVR solenoid
DPF EGR sensor hoses both off
DPF EGR sensor hoses reversed
Damaged EGR orifice tube
Damaged EGRVR solenoid
Damaged PCM
Perform KOER self-test and look for DTC P1408 as an indication of a hard fault. If P1408 is not present, look for contamination, restrictions, leaks, and intermittents.

start with the less costly items
clean the exhaust ports in the throttle body would require two new gaskets
check the hoses for the DPFE and replace if needed
consider replacing the DPFE sensor cost around 45.00 on e-bay

had the same problem on my 99 with the 4.6 finally replaced the DPFE.
I was lucky as my 2005 Escape uses the same DPFE
I was able to swap them out for a weekend to prove the one on the expy was the fault.

 

[Kermit]

Have you cleaned the exhaust ports thru the throttle body

No but it looks like it's on my list. Have the procedure/video somewhere?