ItsAV8

Hey everyone, first post so I hope this is the right place I'm having some issues with my 93' SC400.

My car has been accelerating poorly since I bought it, and is throwing codes for the knock sensors, so I assumed the acceleration was due to the car being in limp mode. To rule out weak spark as a secondary issue I swapped out the spark plugs with some NGX IX spark plugs and ran a can of seafoam through the engine. This marginally helped, but the acceleration problem persisted; so I swapped out the spark plug wires. After doing that, the four cylinders fed by my passenger side coil pack stopped firing. I am still getting good resistance on all wires, as well as voltage from the wire the coil pack is fed by. I replaced the distributor rotor (noting the contact was dark and looked pitted), cap, and serpentine belt, but the cylinders still aren't getting any spark. Anyone know what could be causing this problem?

Edit: I also tried using a spare ECU the car came with, but the engine just cranked. I have no way of verifying the integrity of the spare or main ECU, but I have driven with both in the past and have never had only one be able to start the car

Problem solved, passenger side Ignition coil was bad despite having good resistance and putting out 90v 👍

sc400bufny

You can try cleaning the MAF sensor.. Not guaranteed it would work, but it would be an easier fix than checking your cams

oldManTan

do not clean the MAF, it will stop working. It's most likely your ignition coil, there's one right in the front of the engine on the top and one by the AC pump. just follow the middle wire off each distributor and you'll see it. unplug one and try to start the car, unplug the other and start the car. whichever one it doesn't start with is the bad coil.

ItsAV8

Would my ignition coil still provide power to the distributor if it's bad? I'm measuring the same voltage and resistance coming from both coils. Also, out of curiosity, why would cleaning the MAF kill it?

djl

I had the same issue probably a year ago, both coil packs measured resistance readings were spot on per Lexus service manual, but the driver side turn out to be bad.

Don't be fooled by a good ohm reading on coil packs, just replace them, around $20 each.

djl

DO NOT CLEAN THE MAF.

It is a Karmen Vortex design with mirrors. Solvent sprays designed for hot wire MAF sensors will destroy them, I learned the hard way.

ItsAV8

I'll replace them this afternoon, thanks a lot!

oldManTan

yep, just don't clean the MAF ever.

Ali SC3

iTrader: (10)

sounds like a classic coil pack failure, and never clean the 92-95 maf's
https://www.clublexus.com/forums/per...ason-poll.html

ItsAV8

Ali, just read through that thread you posted, sounds almost identical to my experience- I'm glad it's an easy fix!