rbipu

Hello Everyone,
On my recent oil change, I noted pungent smell of gas and the oil also appeared quite thin for 10w30. I figured the car must be running very rich. Plugged in my laptop and attached are engine live data results at idle and at 2500rpm. The only thing I can deduce is that yes, my long term trims are abnormally bad, I need pointers on what could cause this. Thanks in advance.

More Vehicle info:

• 2008 Japan Model Lexus IS250
• No mods other than a Mishimoto Catch Can
• No engine codes
• Car idles smoothly and runs perfectly

MikeFig82

iTrader: (13)

At 2500 rpms I think MAF is too low. 8 g/s

I think at around 1000 rpms im reading 6.2x on my 250 at idle. I need to check later on the day.

Try cleaning the MAF sensor with CRC MAF cleaner first.
Check your air filter when is the last time you had it changed?

2013FSport

iTrader: (2)

No load MAF values are totally different than loaded in gear even on flat ground.

Still good advice and check all clamps and hoses looking for vacuum leaks!

MikeFig82

iTrader: (13)

I would recommend to log what the fuel trims are doing out driving around. Short, and Long fuel trims combined should be close to 0.

Both banks should be closely mirroring each other.

rbipu

Thanks for the reply guys,

• I don't have access to a good MAF cleaner as I'm located in Africa but I do have a used MAF that I bought off of eBay and I've installed that and unplugged the negative terminal for an hour.. little to no difference.
• The air cleaner was installed less than six months ago and has less than 1,600 miles on it.
• While I was doing the reset, I also gave the terminals a thorough clean.

I guess whats left to do now is check for vacuum leaks and check fuel trims while driving.

2013FSport

iTrader: (2)

Can you verify the quality of fuel is not the cause? Are there ever fuel quality issues? Although it may not log faults, fuel that does not burn well can elevate LTFT's.

You might just pull a couple of spark plugs and confirm they are clean and not sooted up with carbon.

2013FSport

iTrader: (2)

One more thing. If the engine acquires a lot of idle time it can increase piston ring blowby and increase the oil smelling like gas.

Buy a can of Yamaha Ring-Free. It is somewhat expensive and add it to the fuel. It will remove deposits from the upper piston and rings.

rbipu

I actually feared short trips may be a contributing factor. The car is mostly driven by the wife and her commute is quite short. Car seldom sees the highway! I just thought the long term trim indicates there's a bigger issue at play.

It's good you've mentioned the plugs. I did replace them a while back and some were not sooty per say but appeared wet and smelled like fuel. Silly me I didn't take note which cylinders had the issue.

Moisture

How much stuff does your oil catch can catch in between changes?

How often do you change your oil? What is your mileage? Any check engine light?

You might want to start by noting the driver (you wife?) to limit the amount of time she spends idling, try to reduce short distance trip frequency at least until the car is fully warmed up, try to take the car out for a minimum 30 minute highway drive once a week to burn off excess fuel and moisture from the oil supply, if you can.

It could also be a poor quality oil being used and infrequent changes as a contributing factor.

First step would be to check fuel pressure. Next would be to remove your fuel injectors and have a shop inspect the spray pattern using a special machine.

rbipu

The catch can will have a significant amount of blow by after just 1,500 miles. I know 'significant' is relative so I could share a pic with you guys if you'd like.

The car is serviced strictly after 3000 miles and I only use 10w30 Castrol Edge Titanium (gold bottle) imported from the US. The mileage is approx 78K miles and no CEL's.

What is considered normal fuel pressure? I see its indicated in the live data I attached earlier. I was hoping something on there would point me in the right direction.

Moisture

Unfortunately I do not know how to decipher those values. Hopefully someone who knows more can chime in, but in the meantime. You could just do some generic google searches to try and determine what would be considered normal.

My suspicion is your fuel injectors. I think you will need to get them inspected.

Also, the amount of blowby you have noted sounds fairly serious to me. Are you able to source Motul or Redline oil where you live? Or even Renewable Lube BioSyn. Those are good oils to consider after you replace the fuel injectors, but they will not fix your fuel dilution issue until then. I think It wouldn't hurt to move up to 10w40, 10w50 or even 20W50 oil for your circumstances - all of which are approved for your engine. Please refer to your owners manual to confirm.

Please take the car to a mechanic as soon as possible and ask him to inspect the fuel injectors and check fuel pressure just in case. Also, please follow up and let us know once you have determined the issue, if you can.

Best of luck.

2013FSport

iTrader: (2)

Sounds like the short trips are the killer... JM2C but letting it idle longer before driving is of zero help. It does need a weekly run up to temperature for at least 30+ minutes. Ideally if you could pull some hills where it has to work.

FWIW: short trips are considered Severe Duty which as you are doing receive a much shorter OCI. 3k mi is good # for short trips. If you do the Ring Free product, burn it through right before an oil change.

Moisture

In the charts, I noticed that the engines oil temperature did not exceed 87C during the testing procedure. You must allow it to reach 100C (or slightly higher) for a minimum of 20 minutes to burn excess fuel out of your oil supply. Sounds like short distance driving is causing issues with your engine.

Moisture

Some fuel system cleaner - a strong concentration of it will also help.

I was doing some research. It says your fuel pressure is 8050 kPag, or roughly 1150PSI which is insanely high. That must be a mistake or something, I do not see how such a high pressure is even possible. I think your fuel pump is the culprit.

rbipu

Very much appreciate the input guys. I'll try give the car a work out more often and I'll definitely give the products recommended a shot.

Unfortunately where I live, garages that could properly troubleshoot the injectors are non existent. No equipment or the skills required to do so. Only option would be to replace and hope for the best.

Do you think changing the MAF would help? With a brand new one this time.