bygtimaish

hey i just checked my exhaust for you, and i got almost nothing..i definitely did not get the greasy/oily ***** that you got..

purebliss

All is's and gs's run rich it all depends if you make short trips or not. The cars run very rich when they aren't driven much. This a well known issue to lexus. They are trying to come out with a fix. Your lucky your Chech engine light didn't come on.

morris

iTrader: (2)

Dont know about the IS but the GS's run on the lean side with an AF of 14.7

WhoDat

Checked my tail pipe and it's sooty as well visible from the rear.....black burnt in gunk on the crome portion.....not cool man, not cool at all for a car with less than 7500 miles.

l1tech

I think your old mechanic needs to learn new ways. Swabbing the inside of a tail pipe I think went out in the 60's. It is not abnormal for the tips of the exhaust to get some carbon buildup and the amount of it will depend on your driving habits. I would expect to find more buildup on cars that are driven more in town and with shorter trips than cars that are driven on freeways for longer periods of time. However your delareship shouldn't have dismissed your complaint so easily without at least plugging the scanner in and having a look at what's happening.

pocky

iTrader: (12)

From my house to work is about 2 miles. So the car barely gets to warm up. Then home, it's 2 miles. It barely gets driven at all. On the weekends however, it gets driven more. So I'm probably running rich all the time.

I get the black sooty stuff on my Tanabe's. I never really noticed it when I had my factory exhausts. Always gotta clean that off when I wash the car. It would turn the mitts black.

morris

iTrader: (2)

No disrespect but just because you are taking short trips does not mean you are running rich. The car is designed to run at a certain AF and it will run there whether it is short trips or long trips.

nota4re

Incorrect. The brief short trips is likely THE cause of the problem... and it is perfectly normal based on everything I have read in this thread. To explain briefly:

All modern fuel injected cars will run in what is called closed-loop mode the vast majority of the time. In closed-loop mode the ECU is setting injector pulse duration length and monitoring the O2 sensors to insure that they keep bouncing back and forth on achieving 14.7:1 A/F ratio. If, in any event the ECU cannot achieve a perfect 14.7:1, you will immediately get a Check Engine Light and the car will likely revert to Limp Mode (pre-programmed operating parameters and hardly driver friendly). The fact that you are not receiving any Check Engine Lights would mean that you are running at 14.7:1.

BUT.... a modern fuel injected car cannot run in closed loop mode until it has had sufficient time to warm-up. The is especially true of the catalytic converters as well as the O2 sensors. So, when you first start the car in the morning and begin driving - the car will be in a pre-prgrammed, fuel-enriched cold-start mode. The ECU will automatically revert to closed-loop mode and the transition is done seamlessly and that's why you never know/feel any change.

As you indicate you are making predominately short trips with the car and mostly whe the car is cold, there's a "larger than normal percentage" of run time in a fuel-enriched mode. The fuel-enrichened mode is necessary for cold-engine driveability and the build-up that you are experiencing is this coupled with catalytic converters not up to operating temperature.

In summary, I think everything is normal per your description and symptoms.

morris

iTrader: (2)

This really is an aside but I will say that I have run multiple second Gen GS with a wideband and it does not run lower than 14 upon startup and as you point out if it were not in the area of 14.7 then you would get a CEL so I am not sure what you are saying. 14.7 certainly is not rich. If I remember correctly second gen IS's and 3rd gen GS's run at even leaner AF mix's than the previous generations.

THis isnt a 72 chevy malibu we are talking about Lexus, should not have oily residues in the exhaust.

nota4re

Morris,

Perhaps you can re-read my post again... or a primer on modern fuel management principles.

O2 sensors are only capable to indicate to the ECU above/below 14.7:1. They are not reliable, for example, to provide feedback on any other A/F values. This is the reason that ECU's have several operating modes. The other modes are used when the ECU is not targetting 14.7:1. One example is during higher load levels (such as WOT), the ECU will want to run a richer value and therefore will revert to Open-loop... using pre-programmed look-up values and external sensors to determine injector duration. During Open-loop, the O2 sensor input is not monitored.

Another condition where the ECU targets a richer value is during Cold Start Mode. My experience, in contrast with your own, is that A/F's are typically in the mid to high 13:1 during cold start operation.

Like in Open-Loop, while the ECU is in Cold Start mode, the O2 sensors are NOT monitored so you are wrong that a richer value would yield a check engine light. It won't.

Finally, you are likely wrong too about oil in the exhaust. If there's so much il in the system such that enough could make it through the CAT(s) and out to the tailpipe - you'd be talking about a fairly large oil consumption rate, fouled plugs, etc.

What you're seeing is black un-burned fuel together with condensation - both stemming from short cold-start run and stop operations.

There's no smoking gun here.

lobuxracer

iTrader: (2)

All true except we have two wide band planar O2s and two narrow band convention O2s in the 2GR and 4GR engines. So the ECM does know what AFR the engine is seeing within a very few seconds of start up.

Also, as previously mentioned, if there is oil making it to the end of the exhaust, I have no doubt multiple DTCs would be set, and the cats would be glowing a dull red all the time. Bet money it's just carbon with water from the exhaust making it appear oily when it really isn't.

nota4re

That's cool.. I definitely didn't know that any of the OEMs were starting to incorporate wideband sensors. Learn something every day!

optsgirl

I drive my car about 88 miles R/T every day. All highway miles.

Big Andy

The most wear in an engine occurs during start up and short trips. TBH if I only lived a couple of miles from work I'd either walk or cycle. It'd do me and my Lexus good.

phatboyc

No way an engine normally running fuel-enriched cold-start mode from time to time should cause carbon soot on her bumper. This is not normal.