infosponge

Good Day,

I have a 2000 GS300 currently sitting around 286XXX miles. I have owned the car since around 13XXXX miles. When I first bought the car, it died under WOT acceleration and wouldn't restart. I took it to a shop they kept if for 2 months trying to figure it out, during so they replaced the spark plugs and valve cover gasket. Finally had the car towed to Lexus, I was missing a tooth on pickup for the crank sensor. They replaced it and did the timing belt /water pump service and all has been well since for the most part. I've been replacing consumables, brakes, tires, suspension, 2 radiators, but the car has always run great. Yesterday on the way to work the car develops a bad misfire, with blinking CEL, I pull over and read the codes, I had P0446 (x2), P0155(x2), P0303. I turned around and drove home, replaced all spark plugs (they looked terrible), plug wires, 1 broken coil connector, and the 02 sensor. Disconnected Neg battery terminal, reconnected the terminal and started the car back up. Car has a dead miss at idle still, and I keep hearing a clicking noise from the throttle body area of the motor, let the car idle about 20 minutes without CEL, drive car around block, P0303 shows up instantly car is still missing and running poorly. Unfortunately had to drive the car to work today, the CEL would blink for a bit then go off for a bit and continued the cycle all the way to work. Still only shows P0303. I have been reading up on this, so far, my only lead is to go back in and trace the coil back to check for shorts. Any advice or direction for trouble shooting this??

Also, can I rule out a coil pack since I only have the misfire on 1 cylinder but there are 2 cylinders per coil?

Thanks in advance!

infosponge

So I went out to the car on break and hooked up the code reader again, Now I have codes P0300, P0301, and P0303.
Edit: VSC light is on now, and VSC is off.
Also if I clear it the VSC light goes off

lexo98

iTrader: (2)

Some codes are 2 trip codes. They won’t set off the check engine light until they are triggered 2 times

infosponge

Thanks for the reply ^^^^^^.

So an update, I have looked to confirm I do not have a large Crack in my airbox resonator, I have re wired the coil connector wiring to replace the deteriorated wiring,have thoroughly cleaned MAF sensor with MAF cleaner, have cleaned throttle body and blade, have taken primary and secondary resistance checks on all 3 coils (I bought new coils also but they are non oem, I didn't install new coils because the resistance measured identical as all of my old coils, so planning to return them (1a auto).

After doing this & a battery disconnect I fired up the car, it did seem to run a bit better, but definitely still had the misfire. CEL popped up quickly with code P0303 being thrown twice. I allowed the car to warm up, which had no noticeable effect. I tried to Rev it a bit once warm and it seems to misfire as high as I revved it (2800-3000 rpm). At this point I removed the throttle body again to access coils and plugs, I pulled the plugs and #3 still appears new while #s 1,2, and 4 all had a clean light brown hue like I would expect for a plug that had been firing.

*****FYI for anyone working on these, go buy a few feet of every size vacuum line on the car to keep on hand, most lines on my car are breaking upon removal.*****

Tomorrow my game plan is to do a resistance test on the injectors, order Orings and I guess a plenum/intake gasket. Because unless someone has some other idea I need to verify cylinder is getting fuel and try to rule out injectors with 286,000 miles it may be time. I'm gonna look into a diy prior, but I'm assuming I will have to remove the intake to access fuel rail if want to remove injectors. I can say I have always run premium as directed, and have used fuel cleaner additives like Lucas regularly (I buy it buy the gallon) fwiw.

Any ideas appreciated!

DundukovEM

Another possible cause of misfire is the condition of the cylinder head valves (requires a compression test), the ignition controller (bolted to the driver's fender and controls the ignition coil packs).

If you're careful enough, you can connect the spare spark plug to the #3 high tension wire, then wind the stripped stranded wire around the spark plug threads and ground that cable to the vehicle chassis.
Then install the spark plug securely somewhere in the air without touching anything under the hood. Leave the hood open.
This way you can start the engine, let it idle, walk to the engine compartment and visually confirm the presence of sparks.
I've done this before and it saves a lot of guesswork and assumptions.

Or use a pre-made spark tester like in this videos.

infosponge

Thank you for the suggestion, I am planning to rule out the fuel issue first. Once that has been addressed and the issue is not rectified, I will look at purchasing a spark tester to verify spark, will also be looking at doing a compression test if the injector cleaning and/or replacement doesn't solve the issue.

Thanks

dwoods801

A good way to pinpoint the cause of specific cylinder misfires is to relocate anything that could be your problem. So swap the plug to another cylinder, the coil, anything that you can easily switch. The fuel injector is probably a little tough. Make sure to mark everything so if the misfire moves, you’ll know what component u moved. And this gives u a chance to inspect everything. If the car was running great and now has a dead miss, and corresponding DTC, It’s unlikely to be a burnt valve or something that occurs over time. Most likely u have some type of electrical problem in the ignition system.

infosponge

Thank you for the reply, I appreciate it. I agree with your statement, I have swapped the coil, by the time I got home from work and getting parts yesterday I was out of daylight, I currently have a new Intake plenum gasket and new O rings for the injectors, I have rigged up some fuel line that allows me to pressurize the injectors with a can of carb and choke cleaner, then pulse the injector with a 9V battery. When time allows I will remove the injectors, then clean and inspect their flow patterns, I have 2 injectors recently pulled from the Junkyard incase 1 is completely dead or clogged. I am getting off of work early tomorrow so am hoping to get on it then.

infosponge

So today I pulled the injectors cleaned & tested them, replaced cylinder 3 injector, replaced several vacuum lines cleaned intake out even though it wasn't bad at all. Fired it up and got cylinder 5 misfire? Dead cylinder again, when I finished cussing, I pulled cylinder 5 coil and replaced it, after that I fired it to l up and all was well. She is purring like she's supposed to. I was sure I had moved the coils when I replaced the plug wires but I guess I hadn't because I'm pretty sure it was a coil issue.

dwoods801

i am glad it is running smooth again, it seems a little bit unusual that a bad coil could be your culprit if cylinder 3 was your lone cylinder not firing correctly. I am not a 2JZ expert or anything close, but I have been under the impression they run with 3 separate coils that each generate the power for a pair of cylinders. So a malfunctioning coil would have caused cylinders 3 and 4 to misfire and you would have found codes P0303 and P0304. Is it possible that it was the spark plug wire for cylinder 3 not making solid contact with the coil or something like that?
I guess it doesn’t matter if it’s fixed and running good now. But If your luck is anything like mine, you’ll be seeing the CEL again soon.

infosponge

I was thinking along the same lines as you, I think that assumption prolonged my repair, to be fair though the primary and secondary resistance checks were almost identical across all 3 coils I re tested the bad coil upon removal. I did confirm contact with all of the wire leads to plugs prior to swapping coils out. If I have to go back in it for a similar issue I will be numbering everything. I will say I'm excited to see what my milage will do now with all of the new/ cleaned items. I drove about 40 minutes or so yesterday without any CEL popping up, will be doing some highway driving over the holiday time will tell if any CEL returns. The misfire is 100% fixed though so far I'm happy to say. I'm hoping to take this car past 300k miles, wish me luck.

phantomgray

So by you saying you changed number 5 coil, do you mean spark plug? Because to my understanding number 5 is just the plug/boot and the line it shares has the coil on number 2. I am still trying to problem solve my mysterious misfire as well.

infosponge

Hello, My issue was not the coils, but the wiring to the coils, my wiring had degraded to the point i was having shorts in the harness in the valley of the valve cover where the coils sit. Once I fixed my wiring issues the original OEM coils were good to go, I ended up rewiring the wiring going to the coil plugs. I did purchase replacement coils, but didn't install them and left the OEM coils in. Car has been running smoothly since, currently has 298XXX miles, but is down due to some alignment issues causing uneven tire wear. Very thoroughly inspect all your coil wiring on top of the valve cover.