ok so saturday i decided to tune up my 92 lexus ls400, 160k miles because gas mileage was getting bad and it just needed a good tune up:

New air filter
new spark plugs
wires looked brand new so i didnt replace them
new pcv valve
new ECT sensor ( i read somewhere that this can cause poor gas mileage)

Now after I changed all of this, i pulled the EFI fuse to reset the ECU because i was told it was necessary to do it after changing the ECT sensor.

Now, while idling in park, the car seems fine, but once I put it into gear, it starts bogging down like its about to stall, and when i give it gas it initially bogs down but then goes like normal, but sometimes it shakes and jutters.

After doing some research, I cleaned the MAF sensor, IAC valve, and also the throttle body, although all of these were very clean to begin with. Still no luck.

My guess is that by pulling the EFI fuse and resetting the ECU, the computer finally realized that some sensors or parts are malfunctioning, and now is running accordingly. I also realized that the check engine light was not on because the bulb was burnt out, so after replacing it i got 3 codes:

13 - RPM Signal No. 2
25 - Air / Fuel Ration Lean Malfunction
41 - TPS Sensor

Now, am I correct in thinking that by pulling the EFI fuse, the ECU finally realized that some parts are faulty, and thats what is making the car run the way it is?

Also, ive researched some fixes for these codes:
13 - cam / crankshaft sensor , or timing is off (i hope it isnt, but i dont see how removing a fuse could throw the timing belt off)

25 - Fuel injector leak or fuel filter clogged, or main o2 sensors

41 - Pretty sure i just need a new TPS sensor


Any ideas of some solutions to clear codes 13 and 25 and get the car running right again?

Thanks!

 

NEVER EVER visually check spark plug wires. if you want to reuse them at least ohm them out with a multimeter to confirm they're all within range.

your "tune-up" left out the caps and rotors, relatively inexpensive but exceedingly important ignition components. check them, and confirm that the wires are in the right order.

checking your TPS is probably not a bad idea given your codes.
http://www.lexls.com/tutorials/EFI/tps.html

 

i've had 13 aa bunch of times, its always been that upper coil. the symptoms are the car runs really rough (kinda like only running on half the cylinder...)

25 I had to replace main o2 sensors

never had a 41 though...not to be mean but are you sure you put the wires back in the proper postion? I once switched 2 wires and had almost the same problem and replaced a million things only to realize it was swapped wires

 

I changed the TPS last night and got it adjusted, its running a little better but still sporadically the rpms drop at idle, it seems like something is "missing". I pulled the EFI fuse and reset the codes, and the 13 went away for now, but now I have a 25 - Air Fuel ratio lean, and a 26 Air fuel ratio rich. How is it possible to be lean and rich at the same time? Im starting to feel like its the o2 sensors for sure, but would that make it miss like it is? Ill check the wires with a meter later, how would i go about testing the cap and rotors? The ignition coil came up in my research a few times, also may try that.

BTW LexLS.com has been my best friend since friday lol.

Thanks guys

Edit: in regards to that upper coil, its not running VERY rough, only at idle while in gear(in park it idles fine) and when i first hit the gas, after that it seems to get over that 'hump' and it will take off.

Also i used ACDelco double platinum plugs, will these be okay?

 

yeah mine would do the exact same thing with the bad o2 sensors, it would drive fine but everytime i stopped and gave it gas to go again it would bog down like it was going to stall then jerk and take off again. pretty embarrasing with passengers so I finally changed the o2's and it cleared up

I've used the acdelcos, they're good but i usually stick with the ngk's

 

Ok so the spark plug wires and o2 sensors are my main culprits at the moment, can someone verify the acceptable resistances for each? Ive heard under 25k for the wires and between 5.1-6.3 @ 68 degrees for the sensors.

 

ratings for the 1LS are on lexls.com iirc.

 

It turns out the spark plug wires were bad, never again will I go by a visual inspection lol. Also replaced both distributor caps and rotors. Runs like a champ again! Although the CEL code 13 went away and I got 25 and 26, once i replaced the wires and reset the codes the only code i get now is once again 13.