I have a 99 rx. I am getting a miss fire code from the computer. I have had the car looked at by first a local mechanic and then a specialist. The mechanic replaced th spark plugs. The specialist replace the VVT (silenoid?). And the miss fire continues,CAN ANYONE HELP.

 

Welcome to the Club.

The misfire is usually related to the ignition coil, not the spark plug or solenoid, god knows how they came to the solenoid

The ignition coil sits on top of the spark plug.

 

In the photo below are the tops of the 3 ignition coils on the front bank (there are 3 on the rear on the back of the engine). These are really easy to to remove and put back in (just a 10mm wrench unscrews the bolt that holds it in).

 

Hi..
I recently replaced all 6 spark plugs, among tons of other things. My latest code is p1354 VVT Random misfire. and p0302 p0304 p0306 I feel it is improbable for three coils to go out at once. My ocv is clean, my engine has no sludge. Recently, I've replaced MAF 2 o2 sensors 2 knock sensors 2 injectors and the plugs. Every time I fix one code another pops up. NIGHTMARE! My car has had the timing belt replaced 25,000 miles ago. I'm so stumped!
Another tidbit..once I clear the code, the car runs beautifully, until that MIL comes back on...then the car runs rough and jerks and hestitates. Does that sound like a gremlin in the ECM? Camshaft position sensor? I'm grabbing at straws here.

 

Yes, highly unlikely that all 3 coils would go bad at once. I had 5 bad coil codes on one occasion so I bit the bullet and took it to the dealer. Only one coil was bad. Having said that, a bad coil doesn't go away when you re-set the code so something else is causing the misfire. Check this out:

http://us.lexusownersclub.com/forums...howtopic=44742

 

Quick note. I recently had a P0306 code, and the typical rough idle and drive. After scrolling / searching the boards including this thread, I replaced the cylinder 6 ignition coil - vehicle returned to smoothness, code gone. Thanks everyone, once again your posts have helped.