Engine jerking when it's hot
 

My 1999 RX300, 170k, engine starts jerking when it gets hot. I think it called misfiring. Mostly it happens when I stop on red light. When I keep driving non-stop it seems OK. When engine is cold, it's OK. No CEL. Repair shop guys told me, since there's no CEL, come back when things get worse. So, I myself changed all spark plugs. Thanks a lot to Lexmex for very good DIY thread. Nothing has changed. Looks like next things to suspect are fuel injectors and coil pack. I didn't find DIYs for those. So, is there anything I can try to do? Is fuel injector cleaner really works? I heard a lot that they're just nonsense...

OCV's could be failing... Hard to tell without codes...

Missing
 

See my post, i had the same issue. cleaned ocv, iac, maf. With no resolution. I finally took it to the repair shop and the engine had a coil that was going bad but was not giving any codes. The technician went from coil to coil with an oscilloscope and saw where it was misfiring occasionally. The bad part was this coil was replaced several months ago by someone else.

What did the spark plugs look like? Was there one plug that maybe looked worse than the others? Any oil on the ends?

Thanks for replies. Spark plugs were in pretty good condition, I think. At least no damages, no oil. Now I'm going to change OCV. I saw in forum postings similar problem solved after OCV change. I've ordered parts online. I'll post about results after work is done.

So, I've changed both OCVs. Thanks to BearsLexus for DIY. First I thought problem solved. But after some driving I started noticing acceleration problem from stop and sometimes some engine shaking. No CEL. I guess my car keeps telling me, that it is old car. So far, chahged spurk plugs, checked coils, used injector cleaner, changed OCVs. May be now I have different problem. Will continue searching for solutions.

You should also pull both ocv screen filters and check/clean them, it's easy to do and best of all pretty cheap... There is a thread somewhere with pics showing their location, they are located right next to each ocv... I easily cleaned mine with wd40, didn't want to hit them with brake or carb cleaner as they were warm and didn't want to spider web the plastic part of filter

Sometimes it is hard enough to figure problems out with cel codes but even harder when there is no code...

I've been chasing my own gremlins and will keep fidling around until I find a cure for my own...

Did you ever inspect the fuel injectors directly? FI cleaners are a waste of money - coming from a chemical engineer who worked in oil&gas. Pulling FI's is not hard to do. Will look for a DIY and, if I don't find one will make a photo-DIY this wknd.

I agree that FI cleaners are a waste as I have wasted plenty on them without beneficial results...

I have also been wondering how easy it is to pull the fuel rails to check the injectors, can all the injectors be pulled without having to remove the plenum? I have yet to really look into that to know for sure... Rebuilding injectors with new filters/seals should be easy once they are removed.

Well I have to eat my words. The two retaining bolts for the rear rail are tucked between the rail and the air intake, so yes it looks like you've got to go all the way and take off the plenum.

I haven't taken a look but thanks for confirming that everything needs to come apart to get those rear injectors off... I'll have to make sure I will have that added to my things to do when I start the valve cover gaskets so that it can be done all at once...

I actually cleaned both OCV screen filters, when I changed OCVs. (Thanks again to BearsLexus for DIY.) They were dirty but not too bad. I washed them with WD-40. Now my car behaves better than before I done all these works. But not 100% fixed. Now next thing to work with is looks like those Fuel Injectors. So, now I'm studying what I can do myself. As in most cases, back row is hard to reach...