ronhot

New to Lexus and new to the forum. I just purchased a 99 RX300 from a neighbor who moved to Hawaii. I noticed after I bought it ($1,700) and it looks brand new, so I'm not complaining that it has a slight hesitation/stumble just off idle and lack of power, also error codes or CEL. It has 150,000 miles, new plugs (OEM), timing belt has been changed at 110,000 miles. I replaced all the coils, one went bad so I replaced the all, cleaned the MAF, I actually used another known good MAF to test with and I still have the problem. Any other ideas.

AnthonyMtz

First off welcome to clublexus second, you need to go to a local autozone or oreillys and get the codes scanned, that will narrow the problem down more, next what brand and type of spark plugs were used? Also what brand of ignition coils were used? I would check it IAC valve and clean it along with the throttle body, check the OCV valve (oil control valve) my dads rx had this issue and it caused it to misfire and run like crap. If you can get the CEL codes that will help bunches, the things I listed are common issues that are similar to the symptoms you are experiencing.

ronhot

Thanks, I scanned for codes and none showed. I tested the scanner by pulling the MAF connector and codes came up for that. Plugs are NGK, I cleaned the IAC and the throttle body, neither where to badly fouled. The coils are a generic brand, and I tested them by disconnecting the connector and checking for RPM drop. I will check the OCV next.

AnthonyMtz

Ok, I would toss the coils, i tried generics and no bueno, my car hated every single one of them, always use oem toyota/denso ones! They run about 70 a piece you could possibly find the set of 6 for around 300$ it's worth it IMO, mine have 180k on them and they are still going, but for sure you'll need oem coils, the performance will not be as good as factory ones. Also make sure the ngk plugs you use are lx iridium or higher.

10acimport

Have you found the problem yet.
I have the same problem but have not yet replaced the parts mentioned.
Was it your OCV ?
I had one go bad, but the wire had broken off the harness and thru a code.