jaxscuby

So recently my LS 400 started to run rough at approximately 161k.
The fuel system was ruled out after I pulled and inspected the individual injectors for blockage..none..
the research indicated most likely ignition related.
The cel were, P300, P0301, P304, P0308, a mis-fire and them specific cylinder mis-fires.
So here are the step I took to trouble shot my mis-fires.

Bought the following parts,

rotors
distributor caps
spark plug wires
spark plugs
ignition coils

ignition coils at around 161k.
since my father probably need had these parts replaced. I decided to show my Lexus some love and get some replacement parts.
Yes, you could say throwing parts at a problem. But when does a mis-fire code tell you exactly what you need to replace.

first thing i tired was replacing the coils, two, one right on top next to power steering pump and upper radiator hose.
this is the one on the right side or passenger side.

and then the one on driver side or left. this one located right below the distributor on left side.

both were held in by 4 phillips head screws very small #2 screws.

the one on driver side is held in place with a bracket secured by a 10mm short bolt and 14mm nut (do not take this off all the way)
the 10mm is obstructed by a fan belt, but I got it out with 10mm 3/8" on 6" extension.
the 14mm nut was loosened by combination wrench.

the bracket sort of hangs when the nut stays on the stud. that way you don't have try and restart, it already a tight space and barely
allows for the wrench.

So after the coil swaps, no noticeable to the idle.
I also checked resistance with ohm meter and new vs old did not show and change in resistance. so I could have not replaced the coils.
but again, the coils are old and showing some love to my car.

to the plugs I have in the car were ngk iridiums that I had installed in the car when I was having fun with my shifter solenoids awhile back.
so cylinder 1, 4 & 8 were slightly black, or abit on the rich side, which I would expect from a factory tune anyways.

side bar on tuning factory ecus.
I have been tuning another make for the past 10-12 years, from piggy back to reflashing factory ecus and aftermarket standalones.
and have over 40 years of wrenching on everything I have owned. puch moped to porsches. so technically competent enough to wrench
on my Lexus.

back to plugs and wires, finished the swap, gapped all plugs to 0.044", traced and traced again wires to make sure did not screw up
the firing order.

so for a brief time when I restarted the car, it idled like a sewing machine, what I would call usual idle. but as soon as I pressed the gas and revs went up.
blinking cel.

I ran out of time, due other obligations and will have to complete the rotors & caps.

timmy0tool

iTrader: (7)

did this resolve your run rough problem? it's a good idea to post you mileage too so we get a baseline idea of the condition of your old parts.

Banshee365

FWIW you're not troubleshooting. You're firing the parts cannon at it.

jaxscuby

so?

my car

my money

my method to trouble shoot

Banshee365

Sure, I'm just saying that's it's not 'troubleshooting'. That's all.

Losiracer2

Have you already found out if your ECU caps are not leaking and the cause of these codes? That's a very common problem with our LS400s

Oseberg

Someone a few days ago on this forum posted a link indicating that if you attempt to adjust the gap on iridium plugs, you will ruin them.

Are the plugs you gapped iridium plugs?

Oseberg

http://www.globaldenso.com/en/produc...ium/qa_22.html

wolfy53

I think I may have linked him before. But spend some time watching some actual diagnostic videos would be helpful for you. There are ways to diagnose your issues, and not just blast the parts cannon. I linked South Main Auto for you to watch he does a great job. Also you do a search for Scanner Danner on youtube and he does several of these misfire issues.

jaxscuby

so had time to get my car of lift today to continue trouble shooting my mis-fires.

my original suspicions were the rotors and caps, but again since the car was given to me
and the mileage was north 130k, I bought replacement parts, coils, wires, plugs, caps & rotors.
and even bought timing belt kit (100k service)..water pump, crank & cam seals, idler, tensioner for next time.

Sorry no pictures, my youngest was watching mickey mouse all night.
so got started about 0930 am this morning.
It took about two hour to engine cool down, get radiator out, top timing covers off,
then loosened the bottom half of the timing cover (cap/cam sprockets).
The passenger side rotor & cap showed no cause for the mis-fires, just worn.
But the driver side showed a pulverized grey powder from broken rotor base.
about 20% off the base broke across the round base.

finished around 4 pm. a long day.

be careful when re-installing the new rotors, since you can drop the screws, also the distributor caps screws too.

so found out why the car was misfiring and solved the issue.
but I still have to chase a front crank seal leak..

Banshee365

Did you use OE rotors? OE rotors have captive screws so they don't fall out.

the front crank seal is very common so just wait until you do the timing belt to replace the seal. If you already had the radiator out that would have been the best time to knock out the timing belt.

jaxscuby

unfortunately i ran out of time today. if i had a few more hours i would have replaced the
timing belt and pieces parts.

but need the car back on the road. my other car is not back on the road yet.