lexusdave

Site has been a great help with my SC4.

She has hesitated going up hills for a few monthsd now, but has gotten worse lately.

I seafoamed thru cylinders & fuel tank. Changed plugs.

She is knocking/pinging at odd times (no load driving) and I am not getting any error codes.

Tried to remove fuel filter but it is rusted on good. Likely take it to get cut when tank is lower.

Next is possible Ignition Coil Pack (both). Check pic to make sure this is it.

Could it be o2 sensor, catalytic converter with no codes?

Also saw some threads for Off Accel trouble with ECU output.

Any advice is appreciated.

JDMSCVIP

I had the same problem change ur coil.packs I got both for like 120 at advanced

JDMSCVIP

On the pics the coil pack is right under the arrow... it has two clips/plugs... use a 10mm and then a Phillips to take them off the bracket...DONT USE FORCE N BREAK THE CLIPS

lexusdave

Thank you. Did the seafoam, oil change, cleaned throttle control assembly, spark plugs. Reset ECU by disconnecting battery but not what I had hoped for. Pulled the ECU fuse and she is running like a kid again. Thanks for your help.

t2d2

iTrader: (8)

Maybe someone reading this will know the answer. Would that be the 15A ECU-IG fuse (#13 in the manual) in the driver's kick panel? There's also a ECU-B fuse that looks less likely. There's nothing relevant in the engine fuse box that I can see.

Ali SC3

iTrader: (10)

its in the engine bay fuse box its a relay looking thing with a round head on the top. it should say like main efi or something. that resets the ecu.

t2d2

iTrader: (8)

Well that explains it! I figured for sure it would be in the main engine bay fuse box, but nothing there looked related. So, I started looking for ECU stuff in the kick panel location...

t2d2

iTrader: (8)

Hot damn, I think that solved my bucking hesitation problem! I ran it up several hills that had it falling on its face in yesterday's tests, and it passed with flying colors. Sounds like it's worth pulling the EFI/ECU fuse after any tweaks in the engine bay. (Disconnecting the battery doesn't seem to have the desired effect on resetting the ECU.) I had recently cleaned the IACV and throttle body, plus the ECU might have still been storing knock sensor trips even though the CELs were cleared, so lots of old history that needed a fresh start.

Also of note, the engine actually sounds different now, like before it muttered or grumbled and now it growls. I wonder if the ECU was pulling timing and somehow contributing to the knock sensor issues, which in turn pulled more timing? At any rate, if it continues working this well, I know the easy fix for the future.

Sc400NL

Learning everyday , i did the tune up a few weeks ago , plugs wires rotors fuel filter ect and i disconnected the battery only , but i will pulling the efi fuse like Ali mentioned

again ...good info

t2d2

iTrader: (8)

Did you have lingering symptoms?

I had also done plugs/wires and fuel filter within the past two months, and none of it made any noticeable difference. After today, I'm thinking it did make a big difference but wasn't apparent until the ECU was reset.

Sc400NL

no i didn't
i have a low mileage car and it did run smooth but wanted to give it a tune up and hoping for some noticeable improvement but can't tell the difference before and after , the wires had "1992" written on it and after i bought it 6 mounts ago i changed every filter fluid ect
but tomorrow i will try the ECU reset the proper way
i thought i had reset it by pulling the battery cable
a little question though
on my previous car a 3trd gen prelude when i reset the ecu after a mod i had to pull the ecu fuse and let it idle for about 10 minutes without touching the gas pedal and no accessories on like ac or anything to let the ECU "learn" the air/fuel ratio
is it the same with the Lexus ecu ?

t2d2

iTrader: (8)

If everything's running smooth, I imagine you won't see much of a difference, if any. Can't hurt to try, though.

I simply pulled the main EFI fuse and left it that way for 20+ minutes. I don't know that it needed that much time, but it worked... I've read some similar stuff about a specific protocol to follow for the SCs after reset, but then I've also read numerous times that disconnecting the negative battery terminal works on its own. (Maybe the specific protocol is for when disconnecting the battery instead of pulling the fuse? In which case, pulling the fuse is a way more convenient method.) What works for some obviously doesn't work for others.

Ali SC3

iTrader: (10)

you can reset it by pulling the battery cable. I normally pull the positive and touch it to the chassis so it will clear out and leave it disconnected for a few minutes. I think it will even reset almost immediately taking the cable off but I usually wait to be sure.

alot of times when you have random issues with a sc400 check those coilpacks, especially if the power seems like half and the cats are getting hot and ticking alot more than usual. its a common problem with age on these cars. the plug wires not so much of a problem unless they have been pinched or look like they are deteriorating from the outside.

you can start it and let it learn for a minut or 2 and then start driving it, I like to drive it more aggressively when its learning it can actually learn a little better, but there is no wrong way to let it warm, just try and reset it when the coolant is fully cold, as in first start of the morning. if you reset it in the middle of the day and its already warmed up then the ecu wont fully learn and could get confused.

so reset in the morning, and do one good start and run until its all warmed up, that should do it nicely.
If you still have issues its not the ecu learning then.

t2d2

iTrader: (8)

Consider this my walk of shame... After 24 hours of bliss, my bucking hesitation at partial throttle (most noticeable in the 40 mph range) returned. So much for the ECU reset fixing it. Back to the drawing board...

Thanks for the additional info, Ali. The car feels like it's running at full power, so I don't think it's the coils. My cats and/or exhaust to tick a lot after shutting the car off, but I'm not sure how much is normal?

Ali SC3

iTrader: (10)

have you tested the coilpacks? each one has a small 2 wire connector going to it. disconnect one at a time and see if it change how it runs. if it doesnt get worse then you found the bad one. alot of time people wont notice the loss of 4 cylinders on that motor, you would not be the first to think its running fine when its running on 4, in fact it happens all the time.