FR-CYA

Just went back down to the garage to check my oil after about an hour long drive. Oil looks good, was just changed 2 months with only a few hundred miles on it. However, when I sniffed the oil on the dipstick it smelled like gas. The car is cammed with headers, O/R Xpipe and Z06 axle back. It definitely smells a bit rich when driving around. After I get out of the car my clothes smell like gas. Chalked it up to the cam and exhaust setup.

What reasons would I have for a gassy smell on the dipstick? <--So many jokes. I know. I know.

sstonebreaker

Check for an exhaust or possibly an intake leak. Sounds like you're definitely running rich. Use a scan tool to see if you can spot which injector bank is running rich and go from there. Another issue could be a bad injector - if you have one cylinder running lean, the computer will richen up that bank until the extra oxygen goes away, but then you're running rich.

I'm currently trying to track down an exhaust leak myself - same symptoms as you, but I noticed the instant mpg on the DIC drops 4 mpg, from 24 to 20 mpg, as the tach passes 2000 rpm in 6th gear. I mean, 1900 rpm, 24 mpg; 2100 rpm, 20 mpg. I'm guessing as the exhaust flow speeds up, Bernoulli's principle kicks in and starts sucking extra air into the exhaust, fooling the computer into thinking the A/F is lean. But at idle with the hood up, nothing's leaking bad enough for me to hear or see it.

Bill Curlee

You need to make sure that you don't have any SENSOR issues that can cause your TUNE run very rich. O2 sensors are most likely not working properly and that will eventually cause the CATs to fail. Clean MAF, No VACUUM LEAKS, MAP sensor working, etc..

Data Log the PCM and see what your LONG TERM fuel trims are telling you. If they are WAY POSITIVE, it running very rich.

See if your O2 sensors are properly switching. If they are NOT, I would do new plugs, wires, clean the MAF, air filter and install the new O2 Sensors. MAAKE SURE that the O2 sensor "HEATERS" are properly working. If the heater circuit is not function or only providing partial current to the heaters, it will significantly shorten the life of the O2 sensors. \

Cold engine, Turn the ignition ON (engine OFF) after 5 minutes, feel the BODY of the 02 sensors. They should be VERY WARM (hot) to the touch. If not, you have to fix that before you install the new sensors. I can help you resolve that issue if that's the case.

Once all that is sorted out, you need to re-evaluate the long term fuel trims and if it still rich, you need to have someone TUNE the PCM.

BC

neutron82

could just be blowby gasses

C5 Diag

Hello my friend !!
If you don't have a scan tool it's going to be pretty hard to diagnose and you'll just be shot gunning parts !!...as others have responded you have to look at O2 sensors and fuel trims...for me it's "TEST don't GUESS" !!...MAF, exhaust leak upstream of O2, stuck open EVAP purge valve, ,bad injector, bad ECT sensor and probably 5 more I missed....does the car run crappy at idle but OK at higher RPM...well, that's a vacuum leak....I'd get that oil changed if this has been going on awhile. If you need help checking any of those sensors let us know...you have a LOT of talent on this Forum...and as I have told many on this forum you can get a decent scan tool with some graphing features for $100-200.00...you'll probably spend that much on parts that need not be changed !!

FR-CYA

C5 Diag

I personally like the Autel scan tools !!...I'd get something that you can "grow" into especially on a car that's 20 years old. The MK808 is a good one for $499.00 on Amazon. I have the MS906 which is a bi-directional scan tool and has a lot more features.It will turn off injectors, turn on cooling fans...helps to diagnose these things....cylinder balance test, misfire counter, Like I said this thing will pay for itself...and an engine is an engine whether its a four banger or a LT5 Supercharged one. A lot of these sensors operate the same way...you just have to find them. Oh, and BTW let's say your CEL comes on and it's an O2 sensor DTC...it DOESN'T always mean it's a bad O2 sensor...there is a lot more to it !!

93Polo

Are you having any hot start issues? A friend's car had an injector leaking down. Oil smelled like gas and he had hot start issues.

FR-CYA

neutron82

what cam is in it?... do you have a catch can and if so what kind and how is it hooked up?... do you have a wideband in the car?

FR-CYA

aaronc7

Normal to have small amounts of gas in the oil. Gas has such a strong odor it's going to overpower anything else.... normal IMO most likely. If you had tons of fuel in your oil, like a cylinder wasn't firing and constantly spraying fuel into the cylinder and leaking down into the pan you could actually see your oil level rise due to all the fuel in it (ask me how i know... lol). There's obviously a difference in how intense the gas smell is an extreme scenario like that and yours...but it's a little hard to diagnose that over the internet, very subjective.

You and your clothes smelling like gas is absolutely normal with a cammed car and no cats. I actually turn my engine off rolling up the driveway and coast into the parking spot in the garage to keep the fumes down in the garage/seeping into house lol. Yes you're going to smell the exhaust, especially with a cam at low RPMs. Not necessarily a sign of running rich...again, a little hard to diagnose over the internet.

Like some others have hinted at, the car runs closed loop stoich fueling in 99 percent of operation, so its not likely it's running rich or lean-- the PCM will compensate to a pretty large extent. In order for closed loop fueling to occur, the front oxygen sensors need to be working and you can check on that with a scan tool and look at their voltage to make sure they are 'switching' and fuel trims can be indicative of issues as well. If the sensors are not switching, it would trigger a check engine light, but the previous tuner could have also disabled this functionality, so we can't be 100 percent certain. And positive fuel trims would indicate that the PCM is having to add fuel to run at stoich AFR, which actually means 'it's running lean', if anything. But it could be a whole number of issues, so we can't say definitively just based on that. If you had extreme fuel trims either positive or negative, the car should set off a check engine light as well.

Bottom line, since you have a modded car with a bit of an unknown history, I think a scan tool of some sort would be money well spent and probably a good place to start. But it also kind of depends if you feel comfortable with that sort of thing or even have a desire to check things out on your own. Getting a scan tool like mentioned above, or a full tuning suite like EFI Live or HPtuners is the 'best' answer and will have the most capability, but honestly a generic OBD2 bluetooth or wifi dongle that connects to your phone can see all of the generic SAE parameters-- to include things like fuel trims. Specific recommendations depend on what kind of phone you have-- apple generally work better with wifi adapters, android and bluetooth work better together. I have the OBDLink MX, which is on the expensive end of the spectrum, but it's been a handy tool to have in general, for car diagnostics and monitoring when required.

bobs77vet

you can send your oil out for analysis that would give your real info to help you trouble shoot

C5 Diag

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