Spreadhead

I bought the 99 RX300 in Feb. 2016 with 112k. My 99 Jeep w/272k had an engine knock. My best friend had a 99 RX300, original owner, with 242k and only major repair was knock sensor that he did himself. I would have bought his car before he moved over seas but he gave it to his brother. So when my jeep died I went and looked at this one. The CEL was on w/p0125 reading. I used this in negotiations and bought as is. Car fax looked good and timing transmission flush and a bunch of other services was completed at 90k.At the time of purchase it was gettin 16mpg. He was using 87 gas. Next day I go to O'Rileys and the code they got was p1155 not p0125.

I have now driven it 10k. Never reset CEL. But start adding 93 gas. My mileage hits 19mpg. Next oil change due this week and moving to synthetic.

Friday I'm on the road 3 hrs. Stop and go traffic and very hot. I gas up at WAWA (92 Oct) and get on highway. I notice as I got close to 60mph it will not go in to overdrive. Next day I Stop at O'Rileys and I have p0300,302,304 and 306. All misfires and I think a mistake because mpg had continued to rise. I also had code p440 & p446 and p1155. I had him clear codes and at 1.3miles CEL comes on again. I think I didn't get aftermarket gas cap on fully after some reading I've done here.

I skype my friend and he recommended cleaning diod off the air filter. I thought it might be knock sensor but he says I will know that if I press gas and it barely moves. The diod was pretty clean but I cleaned anyway and used the DIY here to walk me through it. I had the battery cable off while doing the cleaning. I put it back together drive 30 miles mainly interstate (the CEL came on again at 1.3miles). I pull off stop at a convenience store buy a soda and get back on interstate to return home. While in cruise I notice the car accelerating to catch up with cruise point set. It had never done this before so I took it out of cruise and notice when I hit the accelerator it takes it a few seconds to engage. This happened all the way home. I drove a total of 60 miles and my average mpgs was 30.

This morning same problem with pushing gas and car not moving but I pulled over pulled the computer fuse. Car runs great then CEL light comes back on at 1.3miles. I drive 35 miles with no problem then get my CEL read and I had p0125 and p1155 and p0170 pending. I did not stop at O'Rileys but another shop.

Where do I start? P1155 is the one consistent code I have received. p0125 has been hit or missed and I really wish I had waited before pulling the fuse before collecting reading today. I bet the knock sensor or airflow sensor would have popped.

I would really like to figure this out on my own and the info I have received here has been priceless

Drcoffee

Check out this thread

https://www.clublexus.com/forums/rx-...ement-diy.html

And I would suggest that you buy a code reader from walmart or Harbor freight for $30. Bouncing back and forth to autozone will just get frustrating.

Spreadhead

Thanks drcoffee! Yea I have one with the blue tooth and the app and it will not work with my car another friend of mine has one very similar and his doesn't work with my either...that's a whole different story...but guess what? I getting ready to run to o Riley's to get my codes read....here is why

I just took car on same trip as yesterday and it ran perfect ( did you hear that? It's me knocking on wood). When the car still was still hesitating this morning I pulled the fuse vs. disconnecting battery. I added some chevron fuel injector to quarter tank then put in 10 gallons. I am not much on a cure in a can and think it was simply a concidience but was glad that I made it.

thanks for the link. initially I didn't understand because it was not a code I was getting....then I read it completely and get it

Spreadhead

I have driven 150 miles since I took the battery cable off and I am getting 29.9mpg...I really hoping it settles back to the 19 mpg after I get some more around town driving

JAB

I don't understand; why do you prefer 19 mpg to 30 mpg?

sktn77a

iTrader: (2)

I don't think you're really getting 30 mpg in a 99 RX300(?!)

Drcoffee

If you are getting 30mpg its probably running lean. But I doubt its actually getting 30mpg.


p1155 references the O2 sensor and 302 304 306 are left (front) cylinders. You can find the upstream Denso sensor at rockauto.com for about $120. I don't understand why its so expensive but it is what it is. They are easy to change but you need an O2 sensor socket wrench ($10) to remove it.

Pzindy

The only time I thought the computer was telling me I was getting 29 mpg, I eventually realized the display was set to average mph, not average mpg.

Spreadhead

Thanks jab and pzindy. When I pulled the battery cable it reset everything. So the average mpg is certainly misleading. When I got the car in Feb. 2016 the average mpg, the one that barely moves, was 16.5. I decided I was going to run 93 gas becaue the manual said 87 wa ok but 93 was optimal. Maybe my driving style was different, maybe it is the gas but around town I get 18.8 to 19. It will tick up to 19 but usually settles at 18.8. I confirmed this the old fashion way over two fill ups.

Drcoffee, my thoughts exactly, I am gonna start with the p1155 code sensor change and work on from there.

salimshah

Tip:

If you want to clear out the stored averages, cycle through the display to the item. Press and hold the cycle button till you hear a beep [almost the same as radio presets].

Salim.

Spreadhead

I am not sure what "lean" means but at 542 miles since I disconnected batter my AVE mpg is 18.1

So today I had the hesitation again. Similarities to the last time is the temp was 85. I had about 40 miles interstate driving at 60 plus mph then it went to stop and go driving and then to a total stand still for nearly 45 mins.. Once I got to my destiny it was simply to drop off paper work then I started back the other way. I got back to work. Car was parked for about 30 mins. i then left work for home and at about 20 miles I noticed when I pushed the gas it hesitatited. I exit at the grocery store and still hesitatited. I push the gas and nothing and then it would kick in. I still have about 10 miles to go so I pull the fuse.

Path forward..my repair skills are below average unless it's a 99 Jeep Grand Cherokee . Ordering "advance" code reader or will buy one at Walmart. Was going to attempt to change Sensor for p1155 error code. Do I need "special" wrench? I have the wrenches in mm's. I was also going to address the p1025 error code...the one by the manifold but my buddy who had the same vehicle said he could never break that one loose. Also going to run another fuel injector cleaner and change the oil. This will be my first time changing it.

These are lofty goals. I am open to any suggestions otherwise I will spend the rest of the evening researching this site.

Animal13

The P1155 is the Air/Fuel sensor visible right behind the radiator. Its about $100 for the OEM Denso one on Amazon. I bought the $12 removal tool but ended up not needing it. Its a 20 minute fix if you are even moderately handy. I just replaced the Knock sensors and while I had the engine apart replaced the #3 spark plug and coil pack which was a mess. I'd start with the P1155 because it will come on consistantly. I used to be able to clear it putting Techron in the gas but when I replaced the sensor it was caked in carbon.

salimshah

https://www.clublexus.com/forums/rx-...135-p1155.html

The job is simple enough but has a potential of going bad if the sensor is stuck.

I really liked one mechanic who outright stated .. if it comes out easy then the change is $xx and if the thing is welded in then it will $zzz.

And make sure you buy OEM and replace the right sensor.

Salim