Hi, Scotty,
I have been a big fun of you. I recently noticed that my 2017 Subaru Forester 2.5 NA (60,000miles, cvt) has strong gas smell upon startup coming from exhaust. The smell goes away after a few minutes of driving. No check engine light and no changes of mpg ( as good as before). As the engine would run rich upon startup to accelerate the warming up process, but I only noticed the smell recently. Should I be worried about it and whether there are trouble shooting I could do? I do have an OBD II scanner at hand.
Thanks so much in advance.
Sincerely,
Paul
Scan it when it starts up to see if its running rich. It also could be your cat starting to go out but I think you would see a check engine light if it was really bad.
@jacksonishere
Thanks for your reply. I will give it a try. Should I measure the AFR to see whether it is a lot higher than 14.7?
I have another dumb question. When the engine starts, it usually needs more gas to be warmed up faster. Does the AFR should stay at around 14.7 even at this stage if running properly?
Thanks for your time and I will keep you updated.
@jacksonishere
Sorry for the typo. I meant to say "Should I measure the AFR to see whether it is a lot lower than 14.7?"
No just measure the fuel trim and it honestly could be something as simple as a little fuel left in the cylinder.
@jacksonishere
I measured the LTFT as -7% and STFT as -2% when my car was idling from start. The lambda was fluctuating between 0.996-1.005. These numbers seem to be in the reasonable range, right? I also didn't notice the gas smell this time, which was there in the past a few months.
Can the smell be caused by that the car was left in the garage for a week (when I noticed the strong gas smell)? I drove my car three days ago when I measured the fuel trim values this time and didn't notice any gas smell.
Thanks for your guidance anyway. It has been fun to figure out what LTFT and STFT mean and what are normal numbers for these two parameters.
Does the smell go away if you idle at park?
@yaser
Thanks for your reply. I haven't checked that. I will check it today and update it later. If it went away at park, does that mean anything? Thanks a lot!
I just want to see if the engine is warm, the smell is still there or not.
@yaser
The smell is not there after the engine is warm. This is what confused me. If there is anything wrong with the fuel injector or oxygen sensors, the smell should be there no matter the engine is warm or cold. Any suggestions are appreciated.
I think the 800 is still too high. I search a bit and apparently the car needs to be warmed up so the car idles at high rpm and I think this is the reason you may smell gas probably from the exhaust. If it is not tripping any code, I think it should be ok. For your peace of mind, you can find a mechanic to check the STFT and LTFT readings to make sure the engine does not run rich.
@yaser
I just checked my car this evening. The engine was idling at 1700 RPM right after start and fell to 680 RPM.
I also measured the LTFT as -7% and STFT as -2%. The lambda was fluctuating between 0.996-1.005. These numbers seem to be in the reasonable range, right? I also didn't notice the gas smell this time, which was there in the past a few months.
Can the smell be caused by that the car was left in the garage for a week (when I noticed the strong gas smell)? I drove my car three days ago when I measured the fuel trim values this time and didn't notice any gas smell.
The car should be okay. Maybe I was just being too paranoid, as Scotty suggested to baby my Subi {black}:crying:
Don't they have a recall right now for that?
@eyreland
Thanks for your reply. The fuel pump recall was not including Forester model. The defective fuel pump seems to cause serious results like engine stall, which i haven't observed in my vehicle. Thanks all the time!
What is the idle rpm when you smell the gas?
@yaser
I will go back to check it later today to get the exact number.
Based on my memory, the RPM stays around 1400 RPM upon startup and drops to 800 RPM after a few minutes. The smell was definitely there when idling at 1400 RPM but I was not sure when it just dropped to 800 RPM. After a short trip, the engine idles at 800 RPM and I found no smell for sure.