M9000

2000 RX300
150k miles

Car ran perfect until one day when I started it it barely ran. It shakes like a V8 muscle car at idle.

Initial codes were P0303 & P0304

Replaced:
3 ignition coils #3,4,5
spark plugs
MAF sensor
Rebuilt ALL injectors

Still getting P0300/P0303/P0304 AND occasionallty P1130 &P1172 or P1171.

IF I pull the ECU fuse before I start the car all gears work until I turn the car off. I can really feel the misfire around 2200 rpm in overdrive on the freeway.

THEN when I RESTART it goes into safe mode and only gears 1-3 work. Sometimes in safe mode the car will run even worse and BARELY run, feeling like it's gasping??? (major backfiring etc) until I hit 3800 rpm and then it catches and goes like a powerband is kicking in???

My thoughts are:
Vacuum leak?
O2 Sensors?
Knock sensor inside engine?
Something else going on inside the motor???

Also:
1. My ABS light was on when I got the car back after the transmission was rebuilt and is not working but the car ran fine so I suspect that is unrelated.
2. There are 2 ground wires near the drivers side strut tower. behind the airbox under the brake fluid resivor. One of them was dangling and I could not find out where to connect it so I just attached it to the block???

Any suggestions would be greatly appreciated!!!

Thank you.

rfakinbile

For the misfiring, I suggest you replace all ignition coils. Confirm the plugs in the cylinders too to be working, otherwise replace with OEM plugs.
The misfiring is responsible for the gear not shifting to overdrive. Knock sensor is out of it except if it does same if no misfiring occurs.

Lexmex

Welcome to the Club.

I would still examine the injectors themselves (including their installation), regardless of the fact they were rebuilt. This motor tends to be really touchy. I will assume that you bought Denso ignition coils, but I would verify the coils are in good order by say switching a coil from cylinder 2 to one of the bad cylinders. You might still have some blockage on the fuel lines themselves and I'd be very inclined to run something like Redline's Fuel System Cleaner. Techron is good, but the Redline stuff is more powerful from my experience). A knock sensor issue will throw a different code.

ABS is unrelated. We have our suspicions in this forum that it is related to accumulation on the wheel sensors, but for many that hasn't solved the issue. I personally disconnected my ABS system because I enjoy the braking without it.

Would be interested to see the pictures of the ground wires in question, but yes I agree, hook them up somewhere, because without them it can cause issues with the transmission and erratic shifting, not to mention electrical gremlins.

I would check every last hose in the engine bay to make sure everything is hooked up, particularly ones coming out of the engine airbox and also the IACV valve below the throttle body on the right side.

M9000

When my mechanic replaced the injectors, seals etc he mentioned that one of them was physically broken too. The net result was my car went from running lean to rich and still getting codes .

the 2 constants in this whole process are p0303 and p0304, with the other codes being often but not always

i suppose i could stop by a lexus dealership and look at where the questionable ground wire traces to on a used rx on their lot...I'll try and take a pic of my offending wire

Lexmex

They can run resistance tests on those coils, however I'd like to know what Lexus says (and I'm sure the rest of our members would like to know as well).

mikey00

The dangling ground wire directly behind the airbox is most likely the one from under the airbox. The airbox is attached with 4 bolts. One of these bolts goes through the ground wire connector underneath the airbox. It's easy to miss this one when removing/installing the airbox as they did when they removed your trans.
Just unbolt your airbox and look under it. If you don't find a ground wire that's it.

M9000

Do you think it has anything to do with my car running poorly???

thomas1

I have found some interesting things about those ground wires. Some of them do not go directly to ground in the harness, So they are either floating at some potential above ground or through some resister network. particularily the ones behind the air plenum on the throttle body assembly... I measured them with a ohmeter....

M9000

So today I went and had my codes pulled again:

P0300
P0301
P0303
P0304
P1130 bank 1 sensor 1

I disconnected the o2 sensor on the manifold behind the radiator...was that the right one? It seems like itmay run a litle better but not a lot. CEL still flashing,rough idle and shakes under load around 2200 rpm in OD

code58

I answered this for you on the other forum.

mikey00

I doubt it. It's just grounded under the airbox. It sounds like you just grounded it at a different point.

Lexmex

I'd still run some cleaner through the fuel system.

M9000

UPDATE...I disconnected the front sensor, wrong one I know and my MPG Increased by 0.5. Today I disconnected the rear sensor, by firewall and my MPG Decreased by 1.

I can still feel the car misfiring...that has remained a constant. Perhaps it's time to dig in & check compression, etc?

UNOHOO

iTrader: (3)

well like they said, you should check the ignition points and AF sensors first, i mean if youve got bad coils then you will burn rich and misfire, how many miles do you have on your car btw?

another idea about it burning rich, not sure if this is it but its an idea, the throttle position sensor on the rear of the the throttle body, if the throttle position sensor is throwing out data saying its letting X amount of air through but is really only allowing y amount of air through then that could explain that, just an idea

you should be able to test this sensor with an ohm meter

ZFORCE

I ran into a similar issue with my car back firing. Here is the link and no one else posted, but I found my problem. Hope it helps. Did your mechanic use the dual electrode NGK plugs? My car likes them and hates the platinum NGKs. Check for a vacuum leak in the intake. Check the coils and the plugs for resistance. I was shocked in that I have never definitively had a bad plug, ever, and now I had 3 on the same car!!

https://www.clublexus.com/forums/gs-...ml#post4372210

Remember, if you find it, post it for others with the same problem.