rkahoi

So in advance I apologize for the long post..just want to get all the info I have in.
Important things first 1999 Rx300—192xxx miles
So About a month ago and a half ago, my wife took the car for an oil change to pepboys….yes I know..first mistake..but have had a few busy weeks..didnt have the time to do it so she took it upon herself---the car was about 200 miles overdue…and the car was running fine for about a week….then she mentioned that the brake light was on…and sometimes would go off so came on this forum and found its just low brake fluid, topped it and was done…while I was in there I noticed that the coolant reservoir was basically empty….no leaks that I could see on the parking and car hadn’t overheated so filled all the way…and for about a week…I drove the car myself for about a week ….checked the coolant and again all gone….filled it back up this time looked thoroughly for a leak…put a carton under the car at night every night to make sure something wasn’t dripping and still nada…started checking it daily and everyday the coolant was going lower..on maybe the 4th or 5th day…turned the car on and it took longer than usual and it had a slight misfire…and check engine light came on plugged it in and code was PO115 engine coolant temperature sensor circuit…found an awesome diy on it..(See below)
Replaced the engine temp sensor plugged everything back and fired it up…it started then died off..i checked and rechecked my work….everything was tight and plugged in…tried restarting several times and it would turn almost to the point of picking up but would die off again...after some research found my symptoms similar to a stuck IACV valve so did diy for it (below) cleaned IACV valve.
closed everything up tried it and still engine turning but not going all the way... ihave checked for vaccum leaks and found none.
I finally gave up and had it towed to a mech...and he checked...he says the front spark plugs were fuel soaked but even after letting it dry out..still not getting anything...the front cylinders have good compression...he doesn't wanna open up the back because he'll have to charge me for an hr job....he is suspecting that the timing may have either jumped or belt is broken....the belt was done about 40k miles ago so I doubt that its the problem but at this point I'm ready for anything...it's gonna cost me about 2hrs labour to get to the timing...with no guarantee that thats it.. and I'm still chasing ghosts...
So thoughts...?
Thanks in advance.

https://www.clublexus.com/forums/ls-...ange-pics.html..

https://www.clublexus.com/forums/rx-...-write-up.html

SomeAznGuy

The coolant you're adding HAS to go somewhere. If you don't see any visible coolant leaks, I'd say you have a blown head gasket on the back cylinders or a heater core leak. But I'd think you'd be able to smell the coolant inside the car if the heater core was leaking. A blown head gasket could cause a no start problem. Maybe have him check the oil to see if there is coolant in it?

kalali

At this point I'd pay the labor and have the mechanic inspect the rear cylinder bank and measure compression. It's very likely that the rear plugs are soaked as well. There are tests such as cylinder leak down test that can effectively isolate the head gasket issues. Sometimes even emission measurements can tell if coolant is being discharged from the exhaust. Make sure your mechanic doesn't start throwing parts at it without systematic test and measurements. Good luck and keep us posted.

rkahoi

I've owned like 3 subaru's so I actually suspected a HG leak having had to replace 2 of them...but searching the forum..found almost no instances of it happening to anyone....so I had already ruled it out....I could be the exception so...I just called him will take an oil sample and fry it see if I find coolant....
I agree the coolant has to be going somewhere...when I took out the old ECT sensor...part of it was slightly damaged..and was assuming maybe that was where the coolant leak was and it was burning off hence why I couldn't spot it..
Again thanks for the suggestions will update when I find out.

rkahoi

Sorry it took me a while...was out of town for work...just getting back to this but....got back on thursday mech told me he had checked compression on rear cylinders they were within spec....he took out cleaned and reassembled the throttle body...he took an oil sample and checked for coolant.....kind of the "old fashioned" where he heated up a metal tray and dropped some on to look for the coolant to burn off and there was none...I know not scientific but we're going for cheap...(he saved me some if I want to send it out for testing).he charged up the battery since it was dead from me trying to start it..plugged it back in... he started it and it ran...I picked it up friday morning... drove it to work..about 40 miles r/t...car drove fine....saturday morning go to start it back up same issues..wont pick up....
He called Lexus to see how much the HG would be while checking...he talked to a tech there who told him he's been there for about 12 yrs and he was yet to see a HG job...
I know for sure it's not the timing because it wouldn't have run for a day again...if it had jumped timing or belt was broken....Now the only thing that I'm thinking is the only other possibility is the ECT sensor that I replaced may be bad...I'm gonna take it out and switch it...just for the hell of it...I am going to send the oil in to have it checked...
Other than that...any more ideas..?
Again thanks in advance...

fastnoypi

id start with some simple diagnostics you can perform yourself like a block test to see if exhaust is pushing into your coolant. I've seen situations of HG failures that pressurize the coolant into the overflow only to be spilled onto the street while driving.
Also you can rent a coolant system pressure tester and add some UV dye to your coolant to help track down leaks.

rkahoi

So..I re-replaced the ect sensor...the car rumbled to life....took a few to "catch"-if thats the right word-...had to pump the gas a few to make it start and after starting let my foot off the gas and it died...restarted it...held on to the gas for a few maybe 3 mins at 2500 rpm then gradually let it go...it almost died but held steady at a very low ~750 rpm...almost like it was about to die...ran this way for about 5 mins...then started..on its own climbing up steadily...and kept going up on it's own i shut it off at about 3500rpm... turned it back on and same thing...would idle just under 1k then start going up....
I mean...at this point wondering if I need to get an exorcist or something along those lines..
@fastnoypi...I'll defn get the kit this weekend and run some pressure tests.
Any more ideas...(other than putting a match or holy water on it which I'm considering)
Thanks again

rkahoi

So...I'm still having issue's with this...the car at start is idling very low...just about 500~ rpm almost to the point of dying and after a little bit of warming up it's going up...on it's own takes it up to about 3k and then jumps up and down...go's up and downbtwn 2k-3k...when I put it into drive...it holds at about 1k and it's very sluggish on acceleration... Yesterday finally a check engine came up..it's P0420 code...which doesn't make any sense with it's current symptoms...I checked all the hoses they're all plugged in and gas cap is fine.. even though the code is not on for this..only thing that makes sense is the throttle possition sensor or something around the throttle body..the sensor is about 25$ so think I'm gonna replace it just because...any other suggestions/feedback?
I did a coolant pressure test and everything is within spec..
Thanks.

RayN

I would suggest to clean your throttle body and maf sensor. Dirty throttle body cause idle problem, sluggish on acceleration. You should be able to find diy on the forum.

salimshah

I would suggest disconnect the battery for about 20 mins.

Pumping the gaspedal to inject gas does not apply anymore. What we have is a throttle position sensor which on stomping the pedal drops the gear and higher rpms sucks more air and injectors start squirting more gasoline. [Practically the ECU measures the air molecules and supplies the amount of gas to get a complete burn].

I would also check the throttle butterfly moves smoothly and returns to close. IACV may need cleaning too (you can compensate by a light pressure on the gas pedal).

Salim

matts6887

Salim; just a quick ? here on the throttle body/butterfly on this note. About how often on average would you say cleaning of that is necessary? or does it depend on if there is sluggish acceleration, etc?. Im not sure when the last time mine was cleaned; however; I have not really had any sluggishness per say yet from mine.

maxSteel

How did you check for vacuum leaks?
http://blog.fcpeuro.com/2014/12/19/l...bd-ii-scanner/

As for the coolant leak, I've had a slow leak for a while at the water seal plate. I never see coolant on the ground, but sometimes I smell it. It's next to the oil filter:
https://www.clublexus.com/forums/rx-...ml#post8849702

salimshah

if a problem happens or for some other reason one has to take the air intake off ... would be a reason to clean it up. It is one of those things (among many) which is better if left alone.

Salim

rkahoi

I disconnected the battery for 20 and reconnected...initially it seemed to be level on the idle but after maybe 5 mins..same flactuation came back...I disconnected a 2nd time and even unplugged the Ecu B fuse...and same thing happened...
The IACV I cleaned initially and recleaned and mech also cleaned....the butterfly is smooth and go's back to close...I cleaned the plates also ..and the whole throttle body and maf while I was in there...
I didn"t understand this part of your reply if you don't mind expounding...

"Pumping the gaspedal to inject gas does not apply anymore. What we have is a throttle position sensor which on stomping the pedal drops the gear and higher rpms sucks more air and injectors start squirting more gasoline. [Practically the ECU measures the air molecules and supplies the amount of gas to get a complete burn].

Thanks for those links...the diy on looking for vaccum leaks was especially helpfull....I just did it and we can rule a leak out too....
in terms of the coolant leak after replacing the ect sensor I haven't noticed coolant loss and after pressure testing the system this weekend...I may not have one...that being said...I haven't driven the car much so I will definetly look for that....
I have cleaned the maf
I'm getting the TPS tomorrow...I'm only replacing it because it't the only cheap thing that makes some sense right now...will update...still open to other ideas..
Thanks for all your suggestions...

salimshah

When you disconnected the battery, it cleared out all the running info and it set the ecu to median position. After running 5 minutes it picked up the sensor information and tried to compensate to unacceptable running condition.

I would start by doing an ecu read [dumb readers will give you any error code] where a smart reader will give you live reading. With the live reading an expert can tell you what the ecu is seeing.

Erratic idle can be due to vacuum leak. Were all the gaskets replaced as recommended?


Pumping elaboration: With carbs, there used to be chamber which stored gasoline and if some one pumps the throttle, it would squirt raw gas into the intake which would jump the rpm. If not enough air was flowing (when engine was not running) one would flood the intake. ECU now meters the air going in and would only allow gas to that would burn completely under ignition.

Salim