rx300 rough idle

[princered72]

I have a 2001 RX300.  160k miles on it.  Runs great except using some oil.  About every 4 tankfuls I need to add about 1 to 2 quarts.  Took it on a trip from PA to Florida and back.  Every fill up had to add 2 quarts of oil.  On the way back the check engine and VSC light came on.  When I got back home I check the OBDs and have P0300, P0302, P0304, P0306.  Is the VSC connected to these codes also?  If not how can I check to see what the VSC codes are?

Spark plugs and coils packs have never been changed in the 7 years I have owned it.  I do not think they were changed by previous owner either, so I am thinking that is the first step.  new spark plugs and coils paks.  Anything else I should be looking at?  

[Filehorse]

By 160K miles I had already replaced two coil packs due to failure.  After another one failed I just replaced the rest of them preemptively.  Plugs are generally good for 100K miles so you are well past that threshold.  A quick Google search on the codes will give you most of the info you need although the codes don't always point directly at the problem. Good luck. https://www.google.com/search?q=P0300%2C+P0302%2C+P0304%2C+P0306&ie=utf-8&oe=utf-8&client=firefox-b-1

[princered72]

I managed to replace all the spark plugs.  Still got a misfire on #2 cylinder but definitely running better.  Bought a new coil pack and replaced it.  Still getting #2 misfire. What next?  I have read where the next step is a new injector or a new A/F sensor.  

 

[jjbrahma]

Hello! In regards to the VSC lights: last week I was driving on a fairly smooth Dallas, tarred road and went over about a 1.5 inch gap (road construction) and my VSC lights came on then about 5 minutes later my check engine light came on. Of course, being poor, I panicked. I have the Car Shield Insurance but they won't cover the sensors on older cars...mine's a 2002 RX300 with around 120K miles. I went to Pepboys and came up with a code of P0400 which has something to do with "evaporative emission system." The guy said it could be anything from the engine to the rear of the car. I immediately started Googling the code and its causes. I ended up on a Mercedes AMG site, by mistake, and saw that people there were having the same issues and that a computer reset was needed. I then got on the Lexus sites and checked them out.

The Lexus people were having the same Issues with the same code and other codes. One man said it was only his gas cap; that got me thinking since I had put a locking cap on last year when gas went sky rocketing again and the long lines were reminiscent of the 1970s. Others were saying that they reset their computers a couple of times a month. Evidently our cars adapt to our driving styles; that also got me thinking about why my cars dash always showed avg. mpg at about 4.7 mpg & never changed.

So, I did what they all suggested and disconnected the pos battery terminal for 24 hours (doesn't have to be that long of time but, it was suggested), put my original gas cap back on and, on Sunday (less traffic) I tore down the highway at about 75 to 80 mph (for 100 miles instead of the normal 50) and watched in awe as my avg mpg climbed up to 55 mpg...not kidding at all. I was alone so I couldn't get a pic but, it was literally reading 55 mpg. Now I'm not naive to believe that I was actually getting that kind of milage but, the gas gauge barely moved a cm. and when I got back into city driving it started reading 35 to 38 mpg, depending upon my speed; and it still is!

The guy at Pepboys said another RX300 had gone in the day before me with the same VSC & check engine lights on & confirmed what the man on the Lexus site said also, check the vacuum hose on the air filter housing...it fixed the previous RX300 but not mine. So I went the other route, described above, and now the lights are off, the car is running so much smoother, since I noticed it also had a rough idle and sounded rough from the tailpipe.

So far, the lights are still off, the avg mpg reading is either a miracle or I need a new computer (hopefully not) and it is running like a brand new car. Anyway, what I did is worth a shot. Try it before going to a mechanic for the $70.00 diagnostic reading.

Good luck!

[princered72]

ok installed a new injector in #2 cylinder.  Still getting misfire in #2.  Any other suggestions?  I am going to check compression.  What should compression be?

[Filehorse]

If all this started quickly it's probably not a compression-related issue.  Have you checked to be sure the #2 coil is actually  firing..??  You didn't say anything about having replaced that coil and they are a weak spot.

[princered72]

yes I did replace the coil.  Pulled the plug again and it looks to be firing also.  When it first started I got P0300, P0302 codes.  Also noticed where the muffler connects to the exhaust pipe from the catalytic converter has a hole in it.   This apparently happened when I got the first codes.

When I got the codes I was on a highway running at 70mph.  I pulled off the highway to go to a restaurant and as we pulled into the parking lot I noticed rough idle.  The check engine and VSC light both flashed then stayed on

[princered72]

Finally was able to do a compression test.  #2 cylinder very low compression, 30 to 40 if that.  #4 and #6 about 110.  Next step is to determine if it valves or rings.  Guess next is a leak down test. 😞

[Filehorse]

Unless you're a hardcore DIYer you're getting into an area where you probably need to know a reputable independent Toyota/Lexus shop.  I think the #2 cylinder is in the front bank of cylinders so at least it'll be a LOT easier to access.  Still, with only 120K on the odometer you could pull the head(s) and pony up the $$$ to address the problem and you still should have a LOT of miles remaining on that drive train.  I think my 2000 RX300 AWD had about 245K on it when I traded it in on a Tacoma.  I did have the transmission rebuilt at 135K and it was still going strong when we traded it.  When you find out what the root cause of your problem is please post a follow up so others can benefit from your experience.

Good luck..!!

[princered72]

Squirted oil into #2 cylinder, no change in compression.  Cylinder #4 and 6 and #1 are all at about 140.  Talked to 2 mechanics and both said at 160k probably not worth it.  One mechanic thought even if the heads were done I might have an underlying ring problem due to the amount of oil it was using on a trip to Florida and back.  I had to put about 1 to 2 quarts in at every fill up.  He is very familiar with RX as he has a number of customers with the same model over 210k miles.

If either mechanic were to do the work, reworking or replacing both heads would be $2k plus.  I found a reman head at RockAuto or Advance for about $480.  Just not sure which part number is which as they are referred to as Left or Right.  I am figuring the Right one would be the front one in my car.  Anyone know for sure and what part number would be?

Since it is the front I am considering doing it myself.  Maybe tackle the rear one at a later date.