Multiple Error Codes

[Biniecki]

My truck has been running a little rougher at time when it first starts up and I have noticed fuel mileage decrease. The other day the check engine light came on for the O2 sensor. I hooked it back up last night and found there were also some pending codes. I have listed all the codes below

0153 - Oxygen Sensor Circuit Slow Response (Bank2, Sensor1)

PENDING CODES

0455 - Evaporative Emission Control System Leak Detected (no purge flow or large leak)
0300 - Multiple Misfires Detected
0305 - Misfire on Cylinder 5

I also had a pending code a couple weeks ago for misfire on 6. Sounds to me that there is a problem on the drives side of the vehicle. The O2 sensor code my be due to a leak detected. Not sure if this could cause the misfire codes or not. The truck is a 96 4.0L V6. Anyone have any suggestions on where to start looking?

 

[Runnin'OnEmpty]

The O2 slow response code is most certainly due to a
'lazy' or failing sensor. I'd replace it.

The P0455 code is usually from a leaking fuel cap. Give
the cap a shot of WD-40 in the center valve and see if
that helps. If not, you can replace the cap, they're cheap.
(After erasing, this code will generally stay off for a day
or two of driving before returning.)

The misfire codes could be caused by several things. Maybe
change the plugs and wires first, if it hasn't been tuned up
lately...

 

[jremington59]

On top of the things listed above, when is the last time you ran some quality dry gas/injector cleaner through it? It probably would be a good idea to clean the MAF sensor also.

 

[Biniecki]

I just purchased the vehicle about 6 months ago. The previous owner had said they did a tune up recently but couldnt remember exactly when thought it was in 2012. I did just replace the coil pack over the winter so plugs and wires would effeminately be the next thing on the list. I have noticed the smell of gas more after filling up so its possible that the cap needs to be replaced. I have never ran any dry gas or injector cleaner threw. I have thought about getting some seafoam and running that threw everything. The MAF also hasnt been cleaned. As for the O2 sensor goes is sensor one the upstream or downstream? I would assume its the upstream as it would be the first one on the driver side before the cat

 

[jremington59]

Drivers side, closest to the engine.

 

[Biniecki]

I know where its located just wanted to verify if its considered upstream of downstream as it matters for ordering the part. I would assume upstream as its towards the top/beginning of the exhaust

 

[1992fordgreen]

I know where its located just wanted to verify if its considered upstream of downstream as it matters for ordering the part. I would assume upstream as its towards the top/beginning of the exhaust

Yeah, it's on the left of the transmission bellhousing. Access is adequate.

 

[Runnin'OnEmpty]

.......I have noticed the smell of gas more after filling up so its possible that the cap needs to be replaced.......

Hopefully it's the cap, but it might also be the filler hose
cracked or loose. Cracked hoses are a big problem on
Rangers for triggering that code. You can access the filler
hose fairly easily on an Explorer, I believe. Take a look
at the hose if a new cap dosen't fix it....

 

[Biniecki]

Anyone have suggestions on brand of plugs and wires? Figure motorcraft is probably the OEM

 

[Biniecki]

I replaced the plugs & wires, fuel filter, cleaned the MAF and IAC, and seafoamed. This has seemed to make things a little better. I no longer have pending codes for misfires or EVAP leak. I still have the O2 code as I have not been able to get the old one out yet. May have to take it to a shop and have them get it out.

I am still getting a very weird misfire / rough idle at startup every once in awhile. It seems to happen if the engine doesnt crank long before starting. Normally it has to crank for a second or so before firing up but sometimes it will fire up in about half the time. This is when I seem to notice the problem happening but could just be a coincidence. I have also noticed like a humming noise at idle that will come out of no where. Its a pretty significant hum but will do away when RPMs are increased. I am wondering if the IAC may actually need to be replaced. Any thoughts