RCH701

My 1999 ES300, 250,000 miles has a crippling misfire when it warms up. The idle jumps to 1,500rpm. I checked the throttle position sensor and it had a dead spot in it. But replacing it did not fix the issue. I cleaned the idle control valve (which was sticking and dirty) but no dice. I am now leaning towards the PCM/ECU/ECM whatever toyota calls it. I also unplugged the oil control valve on each bank. No change.

Any other ideas?

lostape45

Any check engine codes?

tomf

Sounds like a bad oil control valve or a dirty oil control valve filter to me. If you had bad oil control valves and you unplugged them you would expect no change. Have you ever replaced the OCVs? This is just a guess based on the limited information you have provided. Of course, as above, the diagnosis would be easier if there were any error codes.

RCH701

I check my OCV filters about 3 months ago. They are spotless. I have codes across the board. TPS, MAF, OCV, front bank misfire, random misfire, a couple of cylinder misfires, catalytic converter. I have always had a code on the cat. I am assuming having all of these codes and the fact that the car runs great when cold that I need a PCM. I got the serial number on mine and I plan to swing by my local u-pull-it today to try and grab one and a VSV for the evap. Mine broke when I was swapping some vacuum lines trying to hunt this down. I currently have the evap bypassed and running all the time.

crwys

I would change the oil control valve. I had the same problem on my 99 es300. Random / multiple misfire, misfire on cylinders. My filters were also clean, but I replaced the valve anyways and it fixed the problem

ES300NZ

.. that won't work. The ECU is coded to the key, and a decoding box under the dash. I wont explain how to work around this because the information would be here for car thieves, but let me just say this, if you're struggling to solve this issue, swapping ECU's isn't something you should try and do.

IMHO: I really don't think it's the ECU. They are quite robust, it will be a sensor, or alot of sensors, or damaged harness, or bad battery, or bad alternator, or a massive short somewhere. All of which the ECU would live through and still try to work. It sounds like the Oil control valves though, I read alot of issues online here and the symptoms just match so nicely.

RCH701

Thanks for the responses. I did look at 7 es300 at that yard today and none had matching serial numbers to my pcm. I found another forum with instructions on how to program a key to an pcm. I read somewhere that they need matching numbers to work with the original key. I replaced my fuel filter a year ago. Fuel filters never seem to actually go bad on street cars. When I had my OCV out to check the filter I used the battery to actuate them and they worked. However, that was then and this is now. I will swap the OCV valves (or get a junk yard set) to see if the misfire changes banks. That will be a $5 fix if it works. Otherwise I will order the PCM for $80.

I was surprised how many toyotas were missing the PCMs at the yard...

RCH701

BTW, how does the VVTi system work? My BMW E36 uses an electric solenoid to allow oil pressure to move a piston which moves a helical displacing collar between the camshaft and sprocket. It is an analog signal that activates when the car breaks 3,000rpm. When they break the engine gets a much throatier idle (think ricer) and lack power in the upper range. Also the BMWs hardly ever break a solenoid, instead the piston seals go out.

RCH701

Never mind about the VVTi. I just googled it. However my suspicion was confirmed. It is an analog on/off system. Since the OCV valves are spring loaded for return then the only reason my car to loose a bank is if
A) the OCV was stuck
B) the PCM was telling it to switch at the wrong time.
I do not believe the OCV is my issue. Then again, this is my third car and I can afford to investigate it further before swapping computers. Updated will be pending.

RCH701

I bought a dorman ocv for my front bank. My filter was clean. The car runs great now.