I have a 1999 lexus ES00.check engine light on and running rough.Ran codes comes up P0301and another time p0300,cylinder misfires.Changed plugs,ran some good fuel injection cleaner.cleaned throttle body and Mass air flow sensor.Nothing worked any other ideas?Thank You

A flashing service engine light means that there is a problem that could damage the engine emissions system.. This could be a bad spark plug or injector or many other reasons. You need to have a scanner put on the system and see what codes are are being set. AND do this asap. Most parts stores will not charge you for doing this.

P0300: Random Cylinder Misfire Condition
http://www.autocodes.com/p0300_toyota.html

P0301: Cylinder 1 Misfire Detected
http://www.autocodes.com/p0301_toyota.html

P0304: Cylinder 4 Misfire Detected
http://www.autocodes.com/p0304_volkswagen.html

How to Fix error code P0300 for random misfires on your car ...

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Oct 15, 2010 - How to Fix error code P0300 for random misfires on your car ... amisfire (code P0304) on a 1999 Mercury Villager 3.3L · How to Fix error code P0500 ... I reset my codes and it ran fine for a couple of days, then I started getting ...

(code P0305) on a 1999 Mercury Villager 3.3L - auto repair

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Sep 7, 2010 - The vehicle is a '99 Mercury Village, 3.3L, with 150000 miles on it. The chief ... How to Fix error code P0300 for random misfires on your car ...

2000 Villager Misfire - Car Forums and Automotive Chat ...

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May 24, 2010 - 2000 Villager Misfire Villager Car Forums. ... i was told that the 3.3L engines of 1999-2002 nissan quests/ mercury villagers are INTERFERENCE engines! ... Hope the following may help, and I will post if my last fix works. ... I have a 1999mercury villager that is showing a random multiple cylinder misfire ...

Rough Idle - 2000 Mercury Villager - RepairPal

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Repair the code issue, because your Villager has OBD-II which is a very helpful Diagnostic system. Upvote (4) ... My 1999 Villager was running poorly; rough idle, lack of power at highway speeds and the engine problem light indicated random miss-fire, etc. I had new spark ... Have code po306 cylinder 6 misfire detected.

P0301 - OBD-II Trouble Code - RepairPal

Here's a link to your misfire. P0301 Dodge Cylinder Misfire Fault Detected ,check this video out. Why Do Engines Misfire P0301 Code

Definition of Diagnostic Trouble Code P0300 Category: Powertrain Definition: Random/Multiple Cylinder Misfire Detected

cylinder 2&3 misfiring, inspect plugs if ok, mark and swap coil packs for known good ones clear codes, run eng brake torque it rev to cause missfire, repeat until check eng, lite comes on, recheck codes if changed cylinders replace coil packs if not, you have two bad injectors.

I found this; if it helps.
The injectors need to be cleaned, if an engine is experiencing any of the classic symptoms of dirty injectors, such as lean misfire, rough idle, hesitation and stumbling on light acceleration, a loss of power, and higher hydrocarbon (HC) and carbon monoxide (CO) emissions.
Lean misfire may also trigger a misfire code and turn on the Check Engine light on 1996 and newer vehicles with OBD II systems. The code often will be a P0300 random misfire code, or you may find one or more misfire codes for individual cylinders, depending on which injectors are most affected.

the web page was:
http://www.aa1car.com/library/2003/ic30336.htm

Hope this helps

OBD II 300 Random/Multiple Cylinder Misfire Detected

When the misfire monitor detects a misfire, it will trigger the check engine light with the specific cylinder number as the last digit in the P030X code. For instance cylinder 1 misfire is P0301, cylinder 2 is P0302 etc. In this case we have either multiple cylinders misfiring, or the computer simply can't determine the specific cylinder, and as such we are left with the P0300 in computer memory.

Possible Causes:

Fuel injectors, related wiring, sensors and computer issues
Running out of gas, or poor fuel quality
Evaporative emissions system (EVAP) concerns: fuel vapors leaking into engine
Incorrect Fuel Pressure
EGR system concerns: leaking EGR valve or restricted ports
Base engine concerns: low compression, valve train problems and timing issues
Ignition system concerns including, but not limited to:
Faulty spark plugs
Faulty coil or related wiring
Ignition module or related wiring issues
Ignition related sensor faults or wiring issues

When cleaning your engine, water/degreaser went down the spark plug ports. Try using a air compressor blow gun to remove the moisture from around the spark plugs and boots. The water was causing the engine to misfire on 3 cylinders at first and as the ports started to evaporate the moisture, the less misfiring was occuring. Dry thouroughly and hopefully coils do not have damage to them. Also check to make sure the boot is making good contact with the spark plug.

P0300 Code - Random Misfire

Symptoms Symptoms may include:

• the engine may be harder to start
• the engine may stumble / stumble, and/or hesitate
• other symptoms may also be present

Causes A code P0300 may mean that one or more of the following has happened:

• Faulty spark plugs or wires
• Faulty coil (pack)
• Faulty oxygen sensor(s)
• Faulty fuel injector(s)
• Burned exhaust valve
• Faulty catalytic converter(s)
• Stuck/blocked EGR valve / passages
• Faulty camshaft position sensor
• Defective computer