throw

When I am driving at a higher speed and I need to pass someone or accelerate, the engine bogs down. I push the peddle to the floor and nothing. This does not happen all the time but it happens. But when I accelerate from a light or lower speeds there does not seem to be an issue. I recently had the value gaskets replaced because of a small oil leak and it seems this problem began after then. I have taken it back to the shop but the problem does not duplicate itself when they test drive it. I was hoping some of you other owners might be able to share your thoughts. Thanks...James

Bgw70

Are you in central Florida?

What year and mileage?

Have tried driving around in the PWR mode?

You could disconnect the battery for 5 min to reset the ECUs

These are just easy things to try before you get more involved.
The fact that it started after they worked on your car may or may not be related.

Also, take it down to autozone or equivalent and ask them to check for any codes.

Cole, chime in here when you have a chance.

Coleroad

Wow need a lot more information. We could throw out ideas all week on this. Especially not knowing what other maintenance has been done. Then with it being an intermittent issue. Is the reason it doesn't happen from a light because it's not at wot like when he goes to pass.

Give us all the information you can think of. Is it actually the transmission slipping on the down shift? Check transfluid level. Check all the other easy things like BGW said.

Poqman

Could also be the throttle body fly by wire sensor or MAF throwing off the mixture. Need a little more info to know if you have an engine or transmission issue.

Coleroad

The throttle pedal its self goes bad on Toyota/ Lexus as often or more than the position sensor. Your right it could be a ton of things.

throw

All great suggestions thank you. So 2002 SC430. 138k miles located in Jacksonville, Fl, full 90k maintenance done 2 yrs ago. Timing belt etc. New Battery. Trans is not slipping, just acts as if no fuel is getting to the engine when accel is pushed as certain times. Trans fluid is good.

Coleroad

I would put a fuel pressure gauge on it. To start narrowing things down.

Bgw70

I will be up in Jax next weekend, are you close to San Jose Blvd? The south side of Jax...if so, I could meet you and look at it, if you want. And if not, no big deal we will try to help you from here.

Coleroad

Does it bog down then take off. Or bog down and not go till you let of the accelerator pedal?

Bgw70

Okay, so let break this down...
If you are driving at higher speed, 80mph, and push it to the floor, nothing?
If you take off from a stop and push it to the floor, all is good up to 100mph, no issues at all, is that correct?

Coleroad

The fact that it's intermittent throws it for a bit of a loop. The question in post #9, is because I'm wondering about the map sensor too.

Harold57

throw, this really sounds like the ECU doing this to you. It is fairly well documented here on the forum.

A quick way to test it out is to place the car in the PWR mode and see if it bogs down there. If not, reset your ECU. There are multiple ways to reset or re-train your ECU: run in the PWR mode for a couple of tankfuls, disconnect your battery for a short time or run through the ECU reset procedure.

There are no cons with running it in the PWR mode other than you have to look at the light on the dash all that time.

Disconnecting the battery will work but will likely lose all your radio settings, seat settings, steering wheel settings, mirror settings, etc

It is quick and easy to reset the ECU and there are no cons to it.
1. Get in your car and insert key. (It doesn't matter if you close the door or not.)
2. Turn the key to the on (not start) position.
3. Press the gas pedal to the floor.
4. Hold the pedal to the floor for five seconds, then turn the key back to the "off" position
(don't remove the key), then release the gas pedal.
5. Wait 2 minutes.
6. Remove key.
That should do it.

Check out the PWR and if that confirms my suspicions, then choose a method and reset your ECU. It will make a world of difference. Let us know how it goes.

Coleroad

Harold, is there an explanation as to what is going on in the Ecu to cause this.

Harold57

Yes, at least, the way it was explained to me. I've never seen it documented though, not that I've looked for it either.

The ECU is programmed to learn how the driver drives and adapt to it. From what I can tell, it is programmed to learn how you drive and help you learn how to drive like a grandma, as it always seems to just add more lag to the driving speed acceleration. Resetting the ECU places it back to factory settings, which is where it should stay IMHO. Actually, it would be nice to be able to adjust a bit more sensitive but that doesn't seem to be an option without adding some aftermarket circuitry to it or making the adjustment to the bottom of the transmission.

Coleroad

Harold, that's what I expected to hear. I' m just in awe that it goes to that extreme in these cars. I believe you 100% about it on these. I had on other cars only seen them get "lazy ". Low shift points not kicking down gears, that kinda thing. Not bog down like a lumbering lawnmower lol.

Hopefully that's what is wrong and quick and easy to try. With no cost yeah.