I changed the fuel filter for the first time at 130k miles, and 4 days later I noticed a little smell of gas inside the car. 7 days after the fuel filter change, I checked the oil dip stick, and it had a strong gasoline smell. The oil level was at the high mark, it was in the middle prior to the fuel filter change.

The fuel filter I installed was a performance K&N filter, could this have caused the issue? It says it's low resistance filter.

Another issue I've had, since even before the fuel filter change, is engine rattle such as what happens when 1 cylinder misfires. It misfires sometimes at red lights. Check engine light is still off. I've had the rattle due to misfire twice before with failing coils, I replaced them and issue was fixed. I'm waiting for the yellow light to turn on to identify which cylinder is misfiring.

Could the misfire cause gasoline to leak into oil too? So is it the fuel filter or the misfire, or something else?

 

A couple of months back, one of the pintle caps on my rear fuel injector broke, and the o-ring fell off, so the fuel caused misfire and it went also into the oil.
I suggest you service you fuel injectors as soon as possible, replace your spark plugs and change you oil. should not be expensive.

 

Did you get any check engine codes? I still have none other than knock sensor (which I've had for over a decade, need to get that replaced).

 

Yes cylinder number 5 was misfiring P0305, but if the leak is not so serious it might not show up immediately.
I would avoid driving the car until you figure it out.

 

Is that suppose to be a tricky question?

 

I doubt if you will be able to do that. Just bite the bullet, and put in more new oil.

 

Did you ever find out the cause? I am having issues of fuel in my oil aswell.

 

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The most likely cause is a leaking fuel injector.

Remove spark plug coils.

turn the ignitionkey fron off to the on position several time's. Do not start the engine.

remove the spark plugs. Smell each one as you remove them. The stinky plug might also look different than the others.

Chances are good that you have identified the leaking fuEl injector. . Hopefully it's on the side next to the radiator.

 

This is really good advice, simple and about as effective as possible to diagnose an injector that is worse than bad.

As the Brits say....... BRILLIANT!

 

Running with leaking injectors can roast you cats. It becomes exponentially more expensive to fix the longer this is left unattended. Get your injectors serviced with new o-rings, screens, and pintle caps ASAP.

 

I had mechanic check injectors / spark plugs / compression and he said they are fine. It seems to have been bad coils. I replaced all the coils and engine runs better and now the gasoline odor is not strong in the oil, it is weak. I only drive short distances, so I think this is why gas collects in the oil. You are supposed to drive a long distance for oil to heat up and gasoline to evaporate.

 

If your mechanic told you this, then I would start looking for a new mechanic. IMHO

 

I suppose that gas could find its way into the oil if the injector worked properly but the spark plug does not fire.

A good mechanic would identify which ignition coil is not firing. He would replace only that coil. Not all of them.

I mentioned a leaking fuel injector because many 4th Gen cars have leaking ones now.
The symptoms match your exactly.

​​​​​​Welcome back if your oil continue's to smell like gas.

 

I replaced the coils myself, did not want to bother with finding out which one is faulty.
I've asked about this issue on a mechanic forum, they told me that since i drive 1 mile trips only, that I need to take the car on the highway once a week so gas and water evaporates from the oil.

 

Hi @RITE ,

I have a similar problem (which I've made a thread about already) but I discovered the gas smell when doing an oil change. I was also doing short trips and lengthy idling sessions because the car was uninsured for a couple months in the dead of winter and I live in a place with only a corner store ("Town trips" are a once-a-month kind of deal).

After my last oil change the I smell the dipstick as best I can every time I check the oil and have yet to detect any gas odor. And it looks like oil not chocolate milk. So I'm crossing my fingers hoping that actually my injectors are okay, but in the meantime I'm trying to scrounge together the tools and parts necessary to do the injector service myself in the future. I still need an inch-pound torque wrench, a set of metric wrenches, and the hoses that will be replaced. Yesterday I discovered that you can upgrade your plenum to a DE-K one with "dual runners" or something Too bad I'm broke AF. Less focus on BHP; more focus on A-to-B

Did you do the "balance test" where you disconnect each coil while running to detect changes in idle quality (no change=something bad happening in that cylinder). Also, a digital multimeter (DMM) is a good tool to have. I got a $50 brand name, Fluke DMM, shipped from Korea for only 50cad (you guessed it... eBay). The only downside to it was it doesn't do amps but for my purposes this is perfect. CarNToys on YouTube has the info on how to test coils with your DMM.


Good luck, Maxima brother!

 

So gas smell is gone now? I just checked and my coils seem to be fine. It might be injectors for me

 

Testing coils isn't complicated and doesn't need to be made so. Pull the coil pack... Take out the plug, hook up the coil pack and insert the plug in and ground. Have someone crank quickly and if you have/see spark..... GOOD!

Unplug the MAF to prevent firing and don't crank forever.

Real test results is the ONLY way to rule out any part from being the problem. Not what we feel like doing.

 

After driving 25 miles to and from on the highway, I could barely or not at all smell gasoline on the dip stick. But after making like three 1 mile trips in the next couple days, I could smell some again, not very strong, but not super faint either.
I dunno if this is normal, or if its injectors, or something else. Engine runs smooth though, no rough idle or anything unusual.
I think I'll eventually take it to a mechanic for him to smell it and see if its normal or not. I wish I could smell other people's dipsticks to compare lol. I smelled a friends car, and it had strong gasoline smell lol.

 

So I took the car to another mechanic about the smell of gas in motor oil. He checked spark plugs and said they are fine, said since there is no misfires that it's not a faulty injector. He replaced the fuel pressure regulator saying that is the most likely cause of the gas in oil.

However, there still is some gas smell in the oil. I noticed the rubber hose on the new fuel pressure regulator is kinked.. the hose that connects to intake manifold (I believe), could that be causing issues?

 

A leaking fuel system can be cheked. I dont understand why a regulator was thought to be the cause here.
However If they thought it to be the cause by somehow magically raising the fuel pressure, Did they Confirm it and tell you it was higher than Spec..?
Unfortunely the damage is done to the seals from said pressure. The regualtor is a bandade fix, however it is not the "WHY" does my oil smell like Gas.

OK.. Understand. That What you need to have happen to properly Diag this issue is to remove the Intake manifold. Fuel rail also. Flip the Fuel rail over leaving the injectors in place and check them for a Missing Pintle cap, or O-ring thats pushed out. I undersand the car drives Ok from your post. If that is what is found you need to get a service kit. For the orings, Z1 sells the Pintle Caps.

The Pintle cap is what holds the Lower O-Ring in place, as they get old and brittle they fall off or break off, the lower O-ring gets pushed down and starts to seep in most cases. Directly into the Cylinder. When the car is OFF. So When someone says the Injectors are leaking, Unlike most other Top feed cars, Our SideFeed injectors are typically fine, Its how they are sealed into the bore of the rail, They need to be removed by someone who knows what they are looking at.

Check my thread
https://maxima.org/forums/4th-genera...cs-inside.html

 

This (and ur post) are super helpful, Thank you! Would u think that the piston rings (?) would need to be changed out as well? (Or anything else needing to be changed because of the injector seals were leaking?)

 

In most cases just the oil needs to be changed in addition to the Re-Seal not just because it smells of oil, but because gas thins oil, if an over time even without the total failure, Run this way would cause that cylinder for lack of a better word, Self Polish as its washed down Constantly, which again, over time can be the root Cause of a host of other issues that money is spent on, but never really Fixed. Yes it can partially evaporate from the oil but now " whats its new viscosity" the damage can be done if ran over a period of time in that the bearings dont play well with large of amounts of gas or water. The engine can also hydro lock when it finally does 100% fail and push out. FIlling the entire cylinder and exhaust with gas as the Pump runs with no restriction. Its something that happens in 10 seconds or less, and definently not something anyone is ready for when it does. Also Depending on the engines load at that time, it can destroy an engine. Fix this promptly and Correctly the First time. O.P just to be clear, this is not normal and Indicates a Problem you need to address Promplty.

 

Thanks for your input. By the way there is also a smell of gasoline near the fuel pressure regulator, it was there before the replacement as well, but mechanic did not see anything leaking. Where could the smell be coming from?

Regarding the fuel pressure regulator, the mechanic said it had a "weak diaphram" and thats why there was gas in oil. I dunno what that means, can you explain or was he lying lol?

 

Unless he removed the intake and lifted the rail to look at the bottom of the rail, He wont see anything leaking. The drip or leak is inside the head runner at the injectors tip. Which is in the head. When the rail is bolted in place.

Regulator wise would depend on his Interpretation of a weak diaphragm. The system can be set up to test. It would require them to install a inline fuel gauge and test the pressure with no vac and vac applied to the regulator compared to what spec is. Also noting the time in which pressure is bleed off. It all has a spec in the FSM> Typically a weak diaphragm in most cases causes low pressure or a complete bleed off of the system over night with "extended Crank" in the mornings. Even if the the regulator was leaking which is highly unlikely. Fuel still cannot get into the Oil this way. A typical 4th gen intake does infact smell of gas. That's a normalcy but the heavy gas smell in the oil is not. I wont say they lied to you, Ill say just possibly misdiagnosed and or didn't fully address your concerns.

The car does have a specific problem, however it takes the right tech who is interested in the why, instead of packing the parts cannon to diagnose this, and guarantee it.

Do this trick for a few days.. go out to the car and prime the pump 3 times, KOEO, for a few mornings but don't ever start the car. do that a few times and then recheck to see if the Gas smell has returned in the oil. Maybe that could point you in the right direction. Also note the oils Color. it should by now with the miles you say you've driven have carbon staining (be darker slightly) if it is still a really light goldish to clear that can also tell you something. Often times the oil's Consistency is that of water when heavily contaminated

 

Thanks again. But what are the "seals" and "re-seal" you mentioned in your previous posts? I understand the pintle caps would need to be replaced if broken, but what else would need to be replace, which seals? I don't know much about cars. I been driving with gas in oil for prolly a year or more, maybe 3K miles total like this. I will contact the fuel pressure regulator mechanic again to give him the update that nothing was fixed, and will mention to him the pintle cap thing.

 

I belive he means the 2 o-rings that are on the injectors. They are 'rebuild' by putting new pintle caps and o rings on, and hopefully flow test w/ cleaning.

 

These came out of a 1999 model back in 2014 - the pintle caps had cracked leaving a gap for the o-rings to leak. The leaking injectors cooked and clogged the cats. The engine would not run because it could not breathe. I installed new o-rings, screens, and pintle caps at the time. I think it cost roughly $30 to buy the refresh kit.

The car has been running trouble-free since 2014.

 

Just as a data point I had inconsistent starts (usually long cranking or stumbly starts, very occasional quick start) and oil that smelled of gas. Replacing my fuel pressure regulator fixed both.
Old one did not smell of gas though but consistent instant starts immediately after replacement and last 3 oil changes have been gas smell-free.

 

The saga continues lol...

So after the mechanic changed my fuel pressure regulator, I still smelled gas for a few days, then I took it back to him, and we both smelled the dipstick, and there was nothing... completely gas free. He told me there is no gas smell on it, and oil texture is fine, and I should not worry cause he's been doing this for ages. I dunno why that day there was no smell at all, when the day before I could smell it.

After that visit to mechanic the oil didn't seem to smell, although I feel like it was sorta off an on, but not as strong as before. Sometimes I felt like I could not smell anything, or the faintest of smells only. Last time though, I could smell some gas on the dipstick right after I pulled it out before wiping it off. And today I changed the oil and there was some smell although not overwhelming, especially noticeable when I was wiping clean the oil drain pan.

The oil level never increases on the dipstick. I poured 4 quarts in 3 months ago, and drained 4 quarts today. I have no noticeable misfires, and no check engine light, engine runs fine.

A year ago I put a K&N performance fuel filter instead of basic AutoZone one I had before, could that cause this issue? It said it's high flow or something on the packaging. Although there was gas odor in the oil before that as well.

 

I finally took out the injectors and send them out to be rebuild. They appeared in pretty rough condition on the outside, dirty and pintle caps super brittle. I sent then to 'Southern Brothers' located in Florida ($20 an injector). They got the injectors and confirmed they were in rough condition and said some were leaking pretty bad, he said the cleaning (no guarantee) would probably restore the injectors. A few months ago I bought 6 cheap refurbished injectors off ebay, reading the forums made me realize why that was a bad idea. But I was about to send those 6 out aswell to southern brothers. And they said they will take a look at them and can pick the 6 best injectors out of them all to clean.

Definetly was a process to get to those back 3 injectors, some of the hoses are a ***** to get to and most are hard and brittle making them even harder to take off. I stopped being 'mostly' gentle half way through and realized I'll need to change out the hoses anyway. While I'm in there I'm planning ahead and doing a few more things: new gaskets for valve covers, manifold, throttle body, and oil pan; pcv valve, and while taking it apart I found a ton of black granuals in one of the pipes realized it came from the carbon canister, so I was able to grab and install a new one of those. Also from the oil saturated w/gas my small oil leak became pronounced so I will also do a crank seal replacement.

They'll get the injectors next week and see what they say.

 

Keep me updated if you manage to fix the issue finally.