NiceSC400

Hi,
My 1997 SC400 is accelerating roughly above 1500 rpms or so.
Here is the list of things done to the car

Before the problem:
The car died on the express way due to faulty ECM, ECM was replaced with a good used one, car started again.

Fuel pump bypass was done(this was done because I thought the car initially died due to this and not the ECM, so it was done before the ECM was replaced)

Timming belt was replaced and installed correctly.

Found a lot of brittle electrical plugs; coil plugs, TPS plugs, distributor plugs, etc... None of them actually broke except for one; the top coil electrical plug. The plug broke into pieces but I was able to insert the pins into the coil.

The car will start exceptionally fine, it will idle like new and accelerate up to about 1500 fine both in neutral and while driving. No hesitations at all are found below 1500rpms, but once it bumps into the 1500+ rpm region it will hesitate. The engine will still go up to 5000+ but with hesitation that seems to go with more rpm input, in other words; more rpms/gas makes it less hesitant.

No CEL are present and the light is not burned.

Any help would be greatly appreciated!

durps

iTrader: (8)

This should help https://www.clublexus.com/forums/sho...d.php?t=551125

SC400slide

iTrader: (11)

Also a small thing to add to the mix, check for vacuum lines that are lacerated or cracked. There is a large one directly under the TB, where the TPS/IACV sit. It breaks on other people and creates a large vacuum leak.

NiceSC400

Thanks for the advice!!
Ok, I repaired the upper coil plug and it seems to have helped, but I am not even sure. The engine still hesitates above 1500rpms.
I will check for the hose under the TB and other vacuum lines. I already checked the inlet pipe going to the MAF and the noise reductor box, did the pull & push test and idle was stable.
Ok to be clear; If one of the sensors would be bad it should be displayed as a "on" CEL right? Or could it be bad an still not show on the CEL light?
And bad coils wont show as "on" CEL light right, right?
Also I already checked with a scanner and it was clear of codes.
Thanks again!!

SC400slide

iTrader: (11)

Well, here is the list of codes.
As you probably saw, The sensors do trip codes, but not all the time. For instance, if the MAF was dirty, or the IAC was dirty...might not be enough to illuminate the CEL. Reading that your car has no codes, next thing I'd do is check for vacuum leaks. Just hope you find some, it will make things easier...