I'm posting a new thread as my symptoms are slightly different. About a month ago my 99 TL with 100k shook really bad, TCS light came on and could barely stay running for about 3 min or so then went away. It didn't do it again for a few days then the engine light came on and stayed on. It pulled the p4020 code. It does this every few days. I have since changed the spark plugs and added injector cleaner and the reset the codes. The check engine light has not come back on but it has had one rough start. The temperatures have not been extreme. What should be my next step?

 

Welcome

The code P4020 is for Catalyst efficiency below threshold.
Usually means the catalytic converter needs to be replaced
The catalyst is not working how it should.
Did it have any misfires ?
Have you cleaned out the EGR port, 99 are known for clogging up easily.

That was the code before, now since theres no codes just drive preferably a highway and see what comes back up.

 

Forgot to mention the PCV valve check that as well. If never replaced then replace it very cheap in the auto parts.

 

Other than the poor starting.....how does the car run on the highway ?
A clogged cat will normally tend to bog the overall performance somewhat.

Try cleaning the EGR passageways as ErickUa5 previously suggested. The '99 model's system was a common issue.
Could be junky fuel. Put a can of Seafoam in your next gas fillup with high octane premium.

Have the TB intake and IAC valve ever been cleaned ? Any other codes or problems ?
Could be a faulty O2 sensor. Check all the wiring connections and grounds.

 

Thanks for the replies. On the highway the car runs great. I saved the code info from my reader. I have not cleaned the EGR port, I will do that and start tackling the other suggestions. Thanks!