TeeRex

Greetings!

I'm a new member here on clublexus. i purchased a 1999 RX-300 about 6 months ago. just completed the normal routine maintenance tasks, incl. RR all the spark plugs (NGK). the only problem i have is an intermittent loss of power (misfire symptom) accompanied with an "exhaust leak", air compressor sound/noise/rattle. this problem can appear with the engine hot during normal driving or cold at start-up. temporarily revving the engine will usually clear it up, return to normal operation. the "exhaust leak" sound is coming from the engine compartment area, but difficult isolate the specific source.

initially i thought the problem was related to a leak/failure in the exhaust system (incl. the CATs) or a blown head gasket. with additional research the problem was looking more ignition related - one of the coils, but i'm not getting a check engine light so therefore no codes to pull.

also, with the car in "P" there is a noticeable vibration/rattle when revving the engine. the vibration/rattle starts at the end of the power curve when the RPMs are decreasing, trailing off.

now, reading some related posts on the forum here, i came across one that seems similar to mine.
pls see: https://www.clublexus.com/forums/rx-...ent-rx300.html

...and a responding member to the above said, "You should first consider the possibility that one or both of your exhaust manifolds are cracked. Common problem."

so with the great minds assembled here, what is the consensus about what the probable cause of my problem is?

i would just like to say i am very impressed with the overall design and performance of this car! fits all of our family' needs perfectly. well, its toyota. DUH! btw, i flushed the tranny with Valvoline MaxLife DEX/MERC ATF and noticed marked improvement in overall shifting performance. i had some flare in 1-2 and 2-3 shifts that is now practically gone. i noticed a lot of discussion on the web about which tranny fluid supplier to use and read positive remarks from RX-300 owners using MaxLife vs toyota, casrtol fluids. i would like to follow-up with a tranny additive. any recommendations? Lubegard?

thank you!

TeeRex

belly up to the tool shed!

would have a dozen replies already on the BMW or merc's forums.

carguy07

No replies because it's a weird *** problem. Does the CEL light work when you start it up? I would think you should be throwing a code. I would chase down that exhaust leak first and then see how it runs.

thomas1

Is the exhaust leak where the flex pipe is below the oil pan? Also sometimes you get leaks between the connection piipe "O" ring gaskets....Does the car shift into overdrive? These are questions we would have....Confused by the no check engine light. check the flex pipe first, with the car on see if you feel air coming through the mesh...if so get it replaced at a independent muffler shot...usually around $100....

maxSteel

I had the same thought as carguy, is the CEL illuminating when you start? The engine gets rough when the computer switches to fail mode.

The general advice on this group is to not flush that transmission.

salimshah

There are far less DIYers for RX vs BMW/Merc. Lexus in general require less tinkering and the target consumer pool is different.

Welcome to the club and I hope you will stay around and help answer the questions that are posted.

Salim

hypervish

That's because all they do is fix their car's all day. We here don't have very many problems with our cars.

Not much we can do over the internet to diagnose an exhaust leak. But, like mentioned, check the flex pipe.

Are there any "pending" CEL's?

TeeRex

thanks to all the members here for the great advice!

no CEL's. the CEL does come on during the normal lamp check, engine start.

driving the car today i can report the engine seems to not be firing on all cylinders when the "exhaust leak" phenomenon begins. the problem is deff more prevalent during cold start-up and less noticeable as the engine warms up.

so the nature of the problem, characteristics, does look heat, exhaust related. tomorrow i will get under the car again and carefully check for exhaust leaks.

question is: if the problem is exhaust related, should i be experiencing 50% to 30% power loss - misfire symptom? even though i'm not getting any CELs i am temped to replace all 6 coils as well.

i agree, the RX-300 is a simple and well designed automobile. easy to troubleshoot and repair - for the majority of failures.

TeeRex

well, not exactly a flush. i disconnected the trans fluid cooling line from the radiator and let the fluid pump out with the car idling in "P" - added another 5 qts until clear. this is a common procedure.

the CEL checks good during engine start-up.

thank you!

TeeRex

ok, today i checked again under the car. i found the problem, exhaust leaking thru the flex exhaust fitting right near the oil pan. i'll have that repaired next week.

thanks again to the all members for the useful advice. i'll contribute my knowledge here on the CL forums in the future.

cheers!

IndyRX300

Wait a minute.... I have a BMW and I dont work on it everyday. Sometimes I take a day or two off.

dnelli

Dude, you never reported back what happened? How is it running now? Did you get it replaced or the flex pipe cut out and an new one welded in place? I know that pipe new is like almost $1200 and a replacement flex pipe welded in by a muffler shop should set you back about $250.

carguy07

The Walker pipe is a direct fit and can be bought for around $60.