Gas in oil at oil change

[bbbjjj2010]

I have an 03 expedition with the 5.4 187xxx miles. Just got my oil changed and found that the oil smelled like gas. Shop wants to flush the intake. I've had problems with the upstream o2 sensor on the passenger side. I've replaced it twice and each time the check engine light would go off. Couple months ago it came back on but I had got laid off from my job so haven't had the extra money to fix that yet. Here lately I've been noticing that I seem to be getting even worse gas mileage (average about 12.8mpg now). I was about to go let the shop flush the Intake and then I was going to go get a new o2 sensor to put on. Before I left though I had a friend over before I left and he knows more about repair than me And he told me he don't think it's related to the o2 sensor like the shop is saying and that it sounds more like a crack in the intake. I'm still not working so before I go start spending money I really don't have I wanted to hear from someone who knows more about this particular vehicle. I still plan on fixing the o2 sensor just don't want to flush the I take if it needs replaced instead. Thanks

 

[stamp11127]

First off, welcome to the site.

Couple of things for you to consider:
1. Replacing the o2 sensor has never fixed your problem.
2. Flush the intake? WTF is that? Clean the egr ports and throttle body I'd believe. This doesn't dump gas in the oil though.
3. Intake cracks, leaking intake manifold gaskets cause the engine to run lean. Higher air to fuel ratio - doesn't show up in the oil as gas.
4. Gas in the oil can only come from two places, 1) you have a dead cylinder (I would expect a misfire code) or 2) you have an injector stuck open. I would expect at least a misfire code for the offending cylinder. My guess is the injector.
5. One other cause can be a failed fuel pressure regulator that is allowing excessive fuel in the cylinders. You should notice a change in the way it runs, may even smell rich in the exhaust.

Find the problem and change the oil. The gas has thinned the oil you have and if thinned enough will cause premature wear on the internals.

A decent scan tool/code reader will show if the upstream o2 sensor is varying the voltage sent to the pcm. Let the data determine if it has failed or not.

 

[bbbjjj2010]

No misfires at this time. I forgot a while back (few months ago) i did have a misfire on cylinder 1 but a new ignition coil took care of that as well as cleared the code. Since then I've not had any misfires. will get codes checked again sometime tomorrow though to be sure.

 

[stamp11127]

While you are having the codes checked, ask them to monitor the upstream O2 sensor. It should show varying, up and down voltage as the engine is running.

If you have a stuck injector, a fuel pressure check with the engine off can be used to determine if that is a cause of the problem. The system is designed to hold pressure with the engine off.

 

[bbbjjj2010]

The shop I prefer to go to today wasn't open by the time I was able to get there so I stopped at auto zone so I couldn't get the voltages today but there is a new code that is rich on the driver side as well and it says plain as day if same code on other side suspect fuel pressure or maf. Three codes in total: p0171, p0174, p0442

 

[stamp11127]

I would bet their scanner will read the O2 sensors, they just don't know where it is.
Should you have them read it again in the future, it is usually under "live data" or something similar.
Good news is your on the way to correcting the problem. Bad news is if you have dumped a bunch of gas out of the exhaust it has taken the cats out.

 

[bbbjjj2010]

I wouldn't imagine it should be too muchbecause I change the oil every 3000 miles and this wad the first time. Plus now that I know of the problem it'll be corrected really soon and then anther pull change. But yeah hopefully it hasn't caused any other damage.

 

[bbbjjj2010]

Finally got the time to fix it. No more CEL. Now to change the oil again. Probably just do it myself since it's been pretty nice out recently.