basketthis

It's getting late here (EST) but after searching all of the other cylinder misfire threads, I couldn't find anything directed at this specific situation and was hoping to get some response or insight by early morning tomorrow before going out and checking all of my sensors with my multimeter with no type of direction.

I own a 1995 Lexus ES300. Engine is a 1MZ-FE for those who don't know this already.

My check engine light has been on for about 1 month and I didn't take it that seriously (I know, I know.... another topic) because the air hose from the intake to the front valve cover broke off inside the large tube connected to the throttle body (don't know the actual name) and needed to replace that large tube. So I figured that was the problem. After replacing the main air intake tube between the throttle body and the air filter, the vehicle ran good for about 1 week. Then the CEL comes on and kind of ignore it for a few weeks. I also started noticing some hesitation and "sluggishness" when accelerating especially between around 10mph and 30/35mph. I can press down on the accelerator and the vehicle won't seem to recognize that I want to speed up just a little (small increase in speed while rolling) until I mash the accelerator to the floor. Then it just down shifts to the lowest gear possible and jerks forward as if I am racing (a little embarrassing when trying to accelerate up on-ramps at a normal rate of speed). Otherwise, I just slowly accelerate and put along like an old grandma down the road. I finally got around to checking it today and this is what came up:

P0300 -- Multiple cylinder misfire
P0302 -- Cylinder 2 misfire
P0304 -- Cylinder 4 misfire
P0306 -- Cylinder 6 misfire
P0155 -- 02 sensor (malfunction I think. Don't remember actual wording)

After reading some other posts I am considering looking at many things. The spark plugs were changed within the last 15,000 miles and I have not had a problem up to this point. I am going to start at the top (with electronics) with testing the resistance on my fuel injectors and coils. I will probably test for spark next.
If all of that checks out, I will continue on to a compression test (not sure what I'm getting myself into as I haven't done one ever) and see if that turns up anything. Then I will determine if I need to adjust my valves (which has probably never been done to this vehicle).

I have a A LOT questions:
Does this seem like the right order to go about things?
Could an 02 sensor cause the type of sluggishness that I am getting?
How often do the coil packs go bad and would the three go bad at once?
Does this seem like a valve clearance thing?
Could this have to do with the fact that my front valve cover has had a leak in it for a while?


ANY HELP IS VERY MUCH APPRECIATED!!

I've tried to provide as much info as I know at this time and will update as I go along with any advice and or problem solving techniques.

GEORGE_JET

I recomend a different order. All of your misfires are on the same bank, the possibility of all three coils, or injectors going out at the same time is too high to begin your troubleshooting there.

You have a valve cover leak, I assume around the outer parimeter. It could also be leaking around the spark plug tubes, look at a couple of the plugs, make sure the outside is not coated with oil.

Then look at the O2 sensor error. Bank 1 sensor 1 provides feedback for fuel trims to bank 1. Bank2 sensor 1 feedbacks to bank 2. Much more likely that one O2 sensor would cause all three cylinders on 1 bank to missfire.

You did not indicate how many miles you have on your car. Going by the age of your car, and the P0155 code, I would probably just replace both main sensors. I prefer Bosch sensors, (after all they invented the O2 sensor), many people recomend Denso. Either one will work. If you buy a universal sensor (which I always do), make sure that you solder your connectors to the new sensors, and use heatshrink tubing. do not use the crimp connectors that come with the sensors.

Once you have fixed P0155, clear the memory on the ECM in order to re-set your fuel trims.
If it is still acting slugish after reseting the trims then I would suggest checking compression, then use a mechanics stethoscope to listen to the injectors.

Try these things, and let us know what you find. Good luck

basketthis

Glad you were able to get to me as I was walking out the door. First stop will be the Toyota dealership for the 02 sensor.

Btw, there are 149,xxx miles on the car.

Thanks a lot George_Jet. I will keep you posted. I had a feeling that all of them misfiring would mean that something other than the coils or plugs was the problem.

basketthis

This is what the exact code text is for the P0155:

# P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

Bank 2 is the front of the engine?

basketthis

FIXED! No more rough engine. No more hesitation. No more check engine light (after one test run). It's back to it's smooth self again! I couldn't be happier.

And, I have to admit, I thought it was a much larger problem than just the O2 sensor... I would have never thought that the O2 sensor would cause the cylinders to misfire especially if the computer is supposed to have backup software in case something like this happens to allow the vehicle to run (which I guess it did, just not efficiently).

Glad I went to my local import parts distributor rather than the dealership (even though I get dealer price) because I would have been out on much more cash.
Saving money (look at MSRP!!!!!!):



I don't know if it means anything to look at the old sensor, but here's what it looked like when I pulled it out:



On a side note my wife had a 97 Ford Explorer with an O2 sensor issue popping up and we replaced all four sensors. Then another pops for just one bad sensor. We replaced that sensor again and the engine code popped once more. We left it alone and the engine ran fine under any condition. With the a/c on it was still fine. It also has a computer backup program that will run the engine and bypass the sensor if it sees failure. For some reason (under these circumstances) this particular Ford vehicle seems to run better off the backup program and it certainly didn't cause any misfires or rough engine. No sluggishness. It did have a little bit of noticeable roughness while warming up but after being warm it was just like nothing was ever wrong (except the CEL, lol). Just thought it was kind of interesting that in this case the Ford ran better than the Lexus with a bad O2 sensor. But, on the other end of the totem pole, the Lexus runs MUCH better with good O2 sensors than the Ford EVER did!

Thanks for your insight GEORGE_JET. I think I got your name right that time (even with the caps ) You saved me A LOT of time and headache by just jumping to the answer! Thanks for taking the time to read my thread.

GEORGE_JET

That's good to hear, you're welcome. I would still recomend changing both of the sensor #1. They have a finite lifespan, most information I have read points to around 50K is a good service interval. I think anything past 100k is too much.