FUEL DILUTION in 96 VW OBDII 2 Liter engine.

[Westerly]

The general info

Car is driven about two to four days a week. During each trip the car is driven about 10 miles each way at speeds of about 50 mph or so.

I have been good about using top tier gasoline most all of the time. With the occasional treatment of fuel system cleaner about every other year. Note: I have not done a gumout regane fuel system treatment since changing the oil last time.

Oil was changed about 5 months ago and only has about 2500 miles on it. Noticed strong gas smell.

Engine runs well no noticable issues with almost 100k on it. Only occasional few seconds of low idling but does not seem to be an issue, just figure that comes with age.

No cel light.

OPinions welcome.

 

[Audi Junkie]

Lazy OXY sensor? Do you scan it for emissions?

 

[Westerly]

Originally Posted By: Audi Junkie
Lazy OXY sensor? Do you scan it for emissions?



Actually no, but I have not seen a CEL for that go on. INterestingly a couple of years ago I did get a code think it was p1033 O2 slow response, but the code cleared itself and never came back.

We don't have emissions testing down here so there is no state inspection for this..

Have any idea how to check the PCV in my car or can this be done using the scan tool?

BTW car has about 100k on it. O2 sensor is the original unit.

 

[Donald]

If in doubt I'd replace the PCV if you cannot remember when you last changed it. Its basically a one way valve so you could attach a short clean piece of tubing to it and see if you can suck air through it with your mouth and also blow air. You should only be able to do one.

Also check the PCV hose and grommet.

Your O2 sensor has probably seen its time.

You could probably look up in manual for a reading to take with a DVM, but one would assume its within allowable specs or the CEL would be on. Still might want to price the sensor.

While you might have a good nose, if you suspect fuel dilution, you need to have a used oil analysis.

I would try a cleaning with Techron, you could have dirty or leaky injectors. But you need a base used oil analysis to start with and then see if a fuel injector cleaning helps.

 

[mechtech2]

How do the spark plugs look?

 

[Audi Junkie]

The injector seals fail too.

 

[Westerly]

Thanks for all the great suggestions. Regarding the PCV valve I really hate to remove that thing as the grommet that keeps it attached to the v cover is almost impossible to remove without breaking the valve itself. However to Audi junkie I DO NOT have the residual oil in the intake hose up from the air filter that often indicates a faulty valve in our cars.. It is almost entirely clean after many miles.
The plastic pipe to the bottom of the engine block and the soft rubber hose elbow connecting to the pcv have been replaced just a few months ago.

Regarding the leaking injector seals....should you be able to smell gasoline at the injectors when the car is running and the injectors are functioning ? I don't notice any thing of that sort.

Agreed about the o2 sensor it is probably near the end of its life, although perhaps the CEL has not come on because of the short driving time not allowing for a full "cycle" to be completed in one drive. I think I will invest in one of these as it is an easy and fairly cheap maintenance item for me.

I would like to get that pcv valve off though and check it. If I wanted to use the blow through technique without removing the valve from the valve cover which opening do i have to blow in.? Hopefully it is NOT the part that goes into the valve cover.

I will pull the plugs and let you know about the condition soon.

 

[Donald]

Originally Posted By: Westerly
Thanks for all the great suggestions. Regarding the PCV valve I really hate to remove that thing as the grommet that keeps it attached to the v cover is almost impossible to remove without breaking the valve itself. However to Audi junkie I DO NOT have the residual oil in the intake hose up from the air filter that often indicates a faulty valve in our cars.. It is almost entirely clean after many miles.
The plastic pipe to the bottom of the engine block and the soft rubber hose elbow connecting to the pcv have been replaced just a few months ago.

Regarding the leaking injector seals....should you be able to smell gasoline at the injectors when the car is running and the injectors are functioning ? I don't notice any thing of that sort.

Agreed about the o2 sensor it is probably near the end of its life, although perhaps the CEL has not come on because of the short driving time not allowing for a full "cycle" to be completed in one drive. I think I will invest in one of these as it is an easy and fairly cheap maintenance item for me.

I would like to get that pcv valve off though and check it. If I wanted to use the blow through technique without removing the valve from the valve cover which opening do i have to blow in.? Hopefully it is NOT the part that goes into the valve cover.

I will pull the plugs and let you know about the condition soon.


As I said the PCV is basically (and only) a one way valve. Which ever end you can get off, put on a piece of new cheap tubing and try and blow through it and suck through it. It should only do one of the two if it is working. Its a PCV (positive crankcase ventilation valve, which means the crankcase vents to the air intake somewhere.

I would guess when most PCV valves fail they are stuck closed. I doubt few vent the wrong way. Shaking it is not a good test.

I also think that blowing through it is only a rough test also. Unsure of the pressure one can blow through their mouth vs the crankcase. Its probably somewhat close but not exact.

 

[Steelhead]

do a fuel pressure leak down test on the fuel rail

probably one or more leaky injectors
common by that mileage

will squirt a cup or more into cylinders that will leak past rings into crankcase after each shutoff.

will dribble while driving also

get a used oil analysis ran on used oil
should be no more than 2% fuel in oil

 

[Westerly]

Again thanks for all the tips. I will have the tests done and will report the results back soon. I'm guessing a leaky injector after shut off because the car starts, runs, drives, and idles perfectly after being cranked.

First I am going to put a bottle of Gumout regane in to the tank to see if that improves anything then to the tests.

Agreed about injector life span. I miss the old mechanical injectors ( Bosch CIS jetronic) on the MKI Rabbit era. They never failed, only the inj o rings became hard and needed to be replaced which cost about a few dollars each 100k miles.

 

[The_Jeff]

Might sound obvious but is your thermostat opening too cold?

 

[moribundman]

Check the fuel pressure regulator and the MAF.

 

[Audi Junkie]

Make sure the coolant temp sender is ok too.

 

[Bobert]

Fuel smell is pretty common in used oil, even with cars with no fuel problems. A used oil analysis would be of benefit rather than chasing a problem which might not exist.

Dyson analysis is better at testing fuel FWIW if you have oil tested. Blackstone seems inconsistent with fuel readings from what I've seen.

 

[Westerly]

I knew this was a fact Bobert, the reason why I was confused is that when I did the paper towel test I didn't notice anything strange compared to previous times when I changed it. I have to say that you do need to get your snout pretty close to smell the fuel odor as well. I have really never got my nose to close to the oil before this time. Guess I was just curious. LOL

The thing that makes sense to me is that since the car has been only driven short distances most of the time lately it probably doesn't heat up the oil to evaporate the volitile fuel. I have actually taken the car out on a long high speed trip and I have noticed that after this the odor is not nearly a noticable.