I just recently bought a 99 rx300 with 90k on it, smoked on strart up so I replaced the valve seals on the cylinder that was burning (cylinder #2), Now ive got cylinder #2 misfire and p0300 codes going on, whats also wierd is once these codes illuminate the check engine light, the Trac off light also comes on and the vehicle will NOT shift in to the overdrive gear... Im totally stumped, ive changed the sparkplug and swapped the injector but with no luck, and one I clear these codes the vehicle is normal untill a couple drive cycles later.... anyone out there ever had this happen and whats the cure, please help!!!!!!

 

Welcome to CL Speedtoys.

How did you know the #2 valve stem seal were leaking oil and cause the smoked on the started up?. To replaced the #2 cylinder valve seal is a lot of work involved, no matter what. You still have to remove the timing belt, valve cover( the front bank), the cam shafts, valve shims and valve springs.

What is your compression reading on the #2 cylinder?

Congrats on your 99 RX and you are one heck of the new owner who know how to do all this stuffs.

 

I would swap out the coil. Check the connection make sure everything is in place. Like Vtt-i said, check your compression. Let us know.
JPI

 

Hi Speedtoys. I have the same problem. Have you solved your issue yet? I have tried cleaning the MAF. Inspected the spark plugs......Do not want to pay Lexus for something I can fix myself. Anyone have any ideas? Origanaly was getting codes p0171,p0300,p0301,p0304,p0306. After cleaning MAF down to the 300 codes only. HELP !!

 

Your ignition coils...right on top of the spark plug.

I also showed multiple on Friday night...turns out it was just one coil, cylinder 2, and I replaced it with one I modified from a current Camry (no Lexus in Mexico ).

Pull off your engine cover and pull out igntion coils (one at a time) on cylinders 2, 4, 6 (1, 3, 5 are behind the throttle body and a little bit of a pain to get to). Do these give spark when you turn on the car?

 

Thanks Lexmex will give that a try. Let you know.

 

Also just a note, but if you are getting a knock sensor code, your RX WILL not go into overdrive on its own. I had this problem, and had my knock sensors replaced and the tranny shifts just fine now.

 

have u checked ur injectors yet? try swaping ur injector connectors and see the problem moves

edit
i dont think it would be the coil because its 1 coil per 2 cylinders

 

Hello there,
I thought I would reply in public so everyone can benefit from this. Do you have access to a good scanner? Here are the following datas we need from you: long and short term fuel trim, reading from MAF , what is the gm/s? Readinng from from A/F( Bank 1 sensor 1 and bank 2 sensor). Also does the misfired occur? Idle? WOT? If you have a good scope I would check the wave pattern on crank sensor. Pull valve covers off and inspect for engine gel.
These engine have one coil per cylinder unlike the older V6( ultilizes the waste spark set up). I would seek an independent lexus shop for their help. But if you need any help feel free to give us a ring 214-221-3135. Ask for jason.
JPI

 

The Coils go bad VERY often as do the mass air flow sensors....Our dealer has only replaced 2 cars knock sensors in 5 years so it does happen but not very often.......COIL and Mass airflow would be the easiest and quickest to check

 

I do have assess to a good scanner and scope but not tell after Christmas. Will have to wait. Thanks for you input this will give me something to look for. Will let everyone know how it turns out. Marry Christmas / Happy Holidays to everyone !!

 

O.K. I will post the final resolution to my problem. Thanks everyone for your help. Took the RX to a local imports shop that I have dealt with many time over the years. They posted the following codes P0300B, P0301B, P0304B, P0306 with pending codes P0300B, P0301B, P0304B, P1130. After a quick trip to the local parts store for a new coil for #1 cylinder. 6 new spark plugs, new timing belt (figured that if I had to get to the back 3 cylinders I might as well change the time belt 108,000 miles). A couple of skint knuckles, $175.00 and 6 hours later we are back on the road. Did not replace the air/fuel sensor (P1130) yet because the light has not come back on. Was thinking that this code was probably the result of the misfire.....we will see. As an FYI: i called Lexus and they wanted $1800.00 for this work.. The back spark plugs are a pain but take the time to remove the throttle body it makes the job much easier. Don't forget to replace your throttle body gasket as well.

 

Yes, you will get a fuel/air sensor error (I got P0171) when combined with an ignition coil failure.

 

Seem like you have random misfired on0 1, 4 and 6 cylinder. What make you think replace the coil on #6 will fix this problem? Please take a good look at your Long term fuel trim.
JPI

 

JP...I have also had friends with other cars who show multiple misfires...yet only one coil is the problem. On the night I had my coil mess up, I also showed misfire in cylinder 1. We checked that one and it was fine turns out it was only one that I had to replace in the end.