97 Es300 Running Slightly Rough At 2500+rpm - Help

[anewman]

My 97 ES300 is running slightly rough from about 2500 RPM and higher as I rev it up (while in Neutral). Not really bad, but rough enough that it is not running like Lexus meant it to. It has 57,000 miles and never had a tuneup or Timing Belt changed. I always run 91 octain gas, and have reciently run SeaFoam through it to clean it out but that did not help much. Does anyone have any ideas as to what I should do to get it running smooth as glass once again? Thanks.

[SKperformance]

Run some more sea foam you may have some excess carbon build up that still needs to be removed.

[anewman]

The gas tank is still half full (with Sea Foam in it).

I ran Sea Foam through the Brake Booster line (1/3 can), and put 1/2 can in the oil.

If I run more through it, which application would you suggest?

I will also be replacing the PCV valve and the Fuel Filter next week just as a precaution. Would Plugs/Wires help, What about a new Timing belt?

[SKperformance]

1/3 of the can in the intake but you add it to the oil and then drain it not keep running it as it is breaks down petroleum products .

Depends on the last time you changed your rear wires and plugs.

[Toysrme]

Plugs, clean the EGR, throttlebody & IAC.

Clean the MAF wire with a q-tip & rubbing alcohol & reset the ECU.

[anewman]

SK / Toysrme - Thanks for your great advice. I have used many of your suggestions in the past and trust your recommendations.

Last night I cleaned the MAF (Mass Air Flow) sensor wires (inside the MAF and at the electrical connections) as mentioned.

I also reset the ECU by removing (for 60 seconds) the 10 amp fuse in the engine compartment labeled ECU-b. I assumed that is the correct way to do that because the car feels much livelier, shifts later, and pulls stronger. GREAT ADVICE!!!!

It is still running slighly rough as before, but I will reset the ECU again after I clean the ERG, Throttlebody, and IAC (with SeaFoam), and replace the PCV valve and fuel filter this weekend. Wish me luck.

[anewman]

OK, I replaced the Fuel Filter, PCP Valve over the weekend. While I was in there, I cleaned the TB, IAC, and EGR valves with seafaom. Put it all back together, and then did another seafoam treatment. Once that was all burned out, I reset the ECU. The car is noticably more powerful, and I sleep better knowing that the TB is shinny now, but after all that, it still isn't quite as smooth as it should be at 2500+ rpm. (original problem) Any other suggestions before I take it in to the dealer?

[SKperformance]

How are your rear plug wires?

Have you changed your oil since the seafoam that is seems to have overdosed on? :)

You may have a slight sludge build up and the oil may need some more cleaning.

Otherwise how are your engine mounts?

[anewman]

I had my oil changed after your suggestion on Thursday. Not only that, but I had them run a full flush cleaner through it too. The oil on the dipstick is as clear as karo syrup. Between that and the seafoam od, I swear this motor is as clean as it can get on the inside.

I have never replaced any of the wires or plugs. Dealer quoted $250 ($50 less than another mechanic). I am not sure how to check the engine mounts, but the shock-like one at the front of the motor is questionable - it has some oil on the lower half, but that may have been from the oil change.

I think I will take it in and have them change the plug/wires and check the mounts too.

[anewman]

OK - so I have not changed the plugs/wires yet, but I did adjust the Throttle Kick-down cable (as ToysRMe describes in a tuner thread) just enough to take out the slack (about 1/8 inch). It shifts like new - Great advice!

Not the plot thickens - the slight rough sound/feel that started this thread can now be heard/felt earlier at around 2000 RPM. Could this be related to the Transmission?

[Toysrme]

Maybe. Check the mounts & check the fluid for the tranny.

[anewman]

From first glance, the mounts look fine. Nothing torn in the dogbone mount. How would I check the transmission shock (dont know the actual name of that thingy???) and the large front motor mount?