What could be causing Fuel Dilution?

[demarpaint]

Originally Posted By: canadiantim
Thanks Guys. I agree the fuel dilution is still too high but the dealer hasn't a clue how to resolve or test so I'm paranoid to let them tinker. My warranty expires in 2 weeks.

Demarpaint, I have tried all of the items you suggested and did get a slight improvement but still seem to be getting a pretty good fuel dilution. The car only has 30k miles on it and all highway...


Here's the problem, it could be the parts I suggested or others, which where also suggested later on. You really need to talk with your dealer and get a tech that is good at trouble shooting. The problem is if there are no codes, I've found that most techs are totally clueless and in the dark. That is not good for you, you need a guy that can trouble shoot.

Here's another problem, it sometimes requires changing parts and guessing a bit, no one wants to pay for that. There is something going on with that engine, it is like finding a needle in a haystack unless you really luck out and get the right man working on it. Good luck, I've been down that road before with mechanics, and after getting tired of having them guess I posted on boards like this and got answers from some good mechanics. I tried their suggestions and solved my own problem. It can take a very long time. Good luck!

 

[canadiantim]

Thanks for the feedback.

Wear metals have been good and so has overall fuel consumption. The engine runs like new. The problem isn't causing the car to throw any codes so I assume it can't be that big an issue while running so I'm suspecting leaking injectors after shut-down. Exhaust smell is rich right after start-up. Usage has been 98% hiway driving with about 5% of that towing a 1500lb trailer. The last 3 UOA have been hiway driving without trailer towing.

The original factory spark plugs I removed were quite dark on the outer edge by the threads but the ceramic and electrodes were very, very light tan with no build-up.

I have max 2 hard re-starts a year when warm after a SHORT drive that mimmicks a flooding condition with long cranking, fuel smell and stumbling after starting. This makes me suspect a leaking injector(s).

Indeed needs some real troubleshooting...
I'm off to my garage to pull the injectors and look for visible leaking.

 

[mechtech2]

Just in case you have not actually checked for hidden codes that do not throw a check engine light, do so.

Exhaust smell on start up is normal. Some cars more than others - the cat is not hot yet, and you are not operating in closed loop O2 yet.

Spark plugs read differently with today's fuels and hotter wider range spark plugs.
But if anything, you seem to be somewhat rich
with a spark plug that is hot enough to burn it off of the insulator.

So why the richness? I'd look closely for one cylinder that is richer than the others - more carbon on the plug or piston top.
This would show a bad injector - maybe more.

If it is even in all cylinders, the front O2 sensor is suspect. it could be sluggish or out of range, and still not throw a code. No matter what else may be wrong, it is the last in the chain - the final say-so.

But any sensor can contribute. Coolant sensors and air temp sensors are important. I'd check their readings/range.

 

[HondaMan]

canadiantim,

I had similar issues with my Honda and this was discussed a few times.

In one of those threads, someone, I forget who, (TeeDub perhaps) spoke of the notion of fuel dilution reaching constant or steady state if you will.
i.e. The ratio of fuel in your oil will settle given many factors including how the car is driven and the fuel level will not continually build after a certain point.

If you accept this idea/notion, then one would just look for oil that will hold up well enough given the accepted fuel dilution.
Big debates on RLI related to this topic of how oil stands up to fuel can be read at length.

 

[demarpaint]

Mechtech2 gave some good info, check for codes. If it were my car and I had the time, and went thru the bother to remove the injectors I would have them serviced. If not I would do a cleaning via the rail, and treat the gas with Redline Complete Fuel System cleaner. Shorter OCI, and a good oil known for its ability to stand up to fuel dilution is a good idea too.

 

[canadiantim]

I had the dealer check for codes and there were none and had them do a cleaning thru the rail prior to these last UOA results.

I checked the injectors myself today and there was no apparent leaking under pressure so I dropped them off at a shop I've used before that bench tests and cleans/rebuilds injectors. They'll be able to tell me if any are way out of spec. They do a full analysis so I'll get back my injectors knowing they're 100% and I'll retest with fresh oil.

Thanks for the ideas.

 

[Gary Allan]

Do they flow match with other cores that they have on hand?

 

[J. A. Rizzo]

One problem I haven't seen mentioned here yet is a leaking fuel pressure regulator. These devices usually run on vacuum, and if the diaphragm inside the regulator ruptures or leaks, it will pull fuel into the intake around the injection system. Symptoms would be hard restarting, reduced mileage, gas smell in the intake, fuel dilution, and maybe others. If you can easily remove the FPR and have a hand-held vacuum tester, you can check for a ruptured diaphragm pretty easily. If it's ruptured, the fix is very cheap. Even cheaper while it's under warranty.

 

[J. A. Rizzo]

I would think a burnt spark plug would be a lean mix rather than a rich one. Rich would be cooler. If extra fuel is being dumped into the intake by a ruptured FPR, the fuel trim from the O2 sensors should be high. If the intake isn't distributing the extra fuel from the ruptured FPR evenly across all 4 cylinders, one or more of them may be running lean or rich. That wouldn't show up on an O2 reading unless there's one for each cylinder or unless the fuel trim goes off scale due to a very leaky FPR and it starts running too rich to compensate for with fuel trim.

 

[mechanicx]

I think before doing all the stuff the OP did, I would send an oil sample to another lab and see if they report the same fuel dilution. About the only way I could see fuel dilution in a well running OBDII engine is if the injectors or the FPR was leaking fuel into the engine. A fuel pressure and leak down test would determine that.

I had a lab tell me I had fuel dilution, and the car already has new OE injectors, and the fuel system has no leak down above spec. Sometimes you have to question a labs interpretation.

 

[demarpaint]

Originally Posted By: canadiantim
I had the dealer check for codes and there were none and had them do a cleaning thru the rail prior to these last UOA results.

I checked the injectors myself today and there was no apparent leaking under pressure so I dropped them off at a shop I've used before that bench tests and cleans/rebuilds injectors. They'll be able to tell me if any are way out of spec. They do a full analysis so I'll get back my injectors knowing they're 100% and I'll retest with fresh oil.

Thanks for the ideas.


If the injectors get a clean bill of health try another lab, if you still come back with a dilution problem you will have to dig deeper. Someone else mentioned changing labs, honestly that is a good idea. I wouldn't put too much faith in a $20 UOA. There are lots of cases where errors have been made with these reports, try another lab to be certain. JMO

 

[sxg6]

For what it's worth, this appears to be somewhat common with pontiac vibe's with the 1zzfe. Now before I get jumped on, only some 1zzfe's, not all of them. The low viscosity probably isn't just due to the fuel, it seems common without fuel dilution. Some say it might be the timing chain in the 1zzfe shearing the oil, and lowering the viscosity.


https://bobistheoilguy.com/forums/threads/chevron-supreme-5w30-4898-mi-2005-vibe-awd-1-8l.124350/

https://bobistheoilguy.com/forums/threads/3-consecutive-6-month-uoas-for-1zzfe-vibe.123630/

Same user as above, but note blackstone's comments.
https://bobistheoilguy.com/forums/threads/05-vibe-4200-miles-using-gc-sampled-in-january.103694/

https://bobistheoilguy.com/forums/threads/05-vibe-4200-miles-using-gc-sampled-in-january.103694/

https://bobistheoilguy.com/forums/threads/exxon-superflo-5w30-2600-mi-pontiac-vibe-1zzfe.17812/

There may be more, but i only searched "vibe" and not 1zzfe's. Personally, I would just change it out more frequently with cheap conventional to deal with the issue.

 

[JustinH]

Have you considered changing your oil brand to something a little different?

I had a rich tune on a supercharged v8 ford, and it would shear mobil 1 5w30 in short order with the fuel...

 

[canadiantim]

Gary, I checked and the lab compares the injector flow to the spec for the injector as well as comparing the set of four to each other.

I'm going to check the fuel pressure regulator as well.
Thanks for the links. I've done numerous searches on BITOG and found none of these. The searches seem to return the same results regardless of the criteria specified.

Interesting info on a few of these engines shearing the oil. Makes me feel a bit better. My drive to work just went from 40min to 3 minutes so shorter OCI's and cheaper oil may be in order.

The lab comes highly reccomended as they do all the oil field sampling for the big oil companies and their equipment fluids. Still not a bad idea to try something different.

I'll post what I find.

 

[J. A. Rizzo]

Originally Posted By: canadiantim
I'll post what I find.


Canadiantim - did you ever get this figured out?

 

[Maritime Storm]

Tim, fuel dilution can happen when you get an extremely rich mixture, possible normal causes of this would be cold starts in a very cold climate(like some parts of Alberta in the winter), other things to put on your check like would be a faulty/incorrect reading temp sensor, lazy O2 sensor could also command the computer for more fuel without setting a code.

 

[friendly_jacek]

This is one weird thread. OP spent a lot of time and money chasing abnormal lab results, yet I did not see the percentage of fuel reported on the lab report!

Labs can and often are wrong. I had a number of garbage results from Oil Guard lab and when I complained about it, the techs did not seemed to be bothered that their results made no sense whatsoever (like 0ppm Fe in used oil and similar anomalies).

Finally, something as simple as idling for a few minutes before oil collection can produce a lot of fuel in oil (happened to me too). OP never answered this question as well.

 

[canadiantim]

All my other car's UOAs have been fine and they are done by the same lab so I suspected it was car specific rather than 7 consecutive errors.

The problem is now solved. My latest UOA came back with no fuel dilution.

I pulled the injectors and had them cleaned and flow tested by someone who knew what they were doing. Had them test each thoroughly for leaking and now all is fine.

Yipee!!

 

[friendly_jacek]

Did he confirm they were leaking?