Strange symptoms

[bbqwolfe]

I drive a lot and the last month or so I have been getting a faint oil smell in the cab. I have looked over the car extensively and not found any leakage. I do not smell oil in the exhaust and the oil level is unchanged. my mechanic and I looked over it together and he removed a vacuum hose to see if any oil had gotten the air intake. Nothing. When I drove away it had loss of power, Since I was very low on gas, I assumed I pushed it too far and filled up. I barely made it home then I had trouble starting it again. I finally got back to the mechanic and he cleaned up the throttle body and things seamed to be better. we thought it might be the 02 sensor but would wait till the engine light came on. The next day, Saturday, It was not great. started knocking, like too much back pressure or timing and then the engine light finally came on. I had do drive it so I did not push it to the knocking point which did not require too much change in my driving style. The strange part is that my gas mileage went up like crazy. I was getting 22.7 on the hwy and 20 in town. Monday I went back to the mechanic and hooked it up and got a P0420/P0430 code Catalytic converter. We reset the light and the knocking went away. As hard as I tried I could not get it back although the light eventually came back on and my gas mileage went back to 19 and 17. I feel like there is something I am not looking at that is not going to show up on the system diagnostics but is making things malfunction. any ideas

 

[bigdude2468]

Why are you ignoring the codes? might be a good place to start...

 

[bbqwolfe]

I'm not ignoring codes. the fact that it came on out of the blue is weird and from what I am reading there are many things that can trigger that error. I'm not interested in throwing $2,500. at an issue that is not the actual problem.

 

[bigdude2468]

Well you are ignoring the codes. 0420 / 0430 are both for low efficiency of the catalytic convertors. This could be caused by bad O2 sensors or plugged catalytic convertors. The O2 sensors can cause the catalytic convertors to plug due to a rich fuel mixture. Your fuel mileage would indicate this is not the issue. You mention "too much back pressure" that would be the catalytic convertor. The burned oil smell could also be coming from the catalytic convertors. How about you pay for an hour of diagnostics to have Ford or another qualified auto repair shop tell you what the problem is. Running a simple fuel trim analysis would determine if the mixture is rich.

Good luck

 

[bbqwolfe]

Thanks That was the more intelligent answer I was looking for. Frankly I don't trust any dealer and very few mechanics so I like to have as much info when I go in.

 

[bigdude2468]

There are plenty of good, honest reputable dealers and independent repair shops. Do some research, find someone you trust and stick with them. Good mechanics are priceless...

 

[XLT16]

I have seen catalytic converters fail and plug in the past for a number of reasons, your symptoms sound like it is is a definite possibility...

http://www.dummies.com/home-garden/car-repair/fuel-system/how-to-troubleshoot-catalytic-converters/

 

[bigdude2468]

When you do have the issue resolved please let us know what the problem was.

 

[bbqwolfe]

+Making progress,,,, I think.. my mechanic reset the whole system to default... the light has been off and no smell for the whole 2 days until i stared doing more city driving. the light and the smell came back with no fluctuating idle to indicate O2 sensor. the other odd thing is the codes are indicating both banks of catalytic converters rather than one or the other. causing suspicion of the mass air flow sensor. He found a tsb for a reprogramming of the PCM. We will see.

 

[bigdude2468]

Almost never does clearing the codes result in the problem going away. Not sure why you think the O2 sensor is not an issue "no fluctuating idle to indicate O2 sensor". I have never found an O2 sensor causing the idle to fluctuate. Not saying it won't do that but I have never witnessed it. There are several reasons why there could be codes for both banks. A faulty mass air flow sensor could result in a rich mixture. A faulty fuel pressure regulator could do the same thing, also a vacuum leak. If the shop you are using does not have a scanner (a really good one can be purchased for under $400, an adequate one for far less) you need to find a new mechanic. A simple scan to check fuel trim will confirm if you are running a rich mixture. The "smell" indicates a catalytic convertor that can't keep up. Driving a vehicle under a rich condition over a relatively short period of time will destroy the catalytic convertors. They are not cheap, roughly $250 from Rock Auto, you need two. With labor you are probably looking at $1000. But, the problem was not caused by the cat's. BTW, a vacuum leak can cause a fluctuating idle.