I have a p0300 and p0301 error code on my 98 tacoma 2.7l 4cly. changed the plugs and wires already. ECL still on. planning to change fuel injectors and o2 censor next.. were and how many fuel injectors are in my truck.. thanks for the help..

P0300 is Random Misfire. 01, 03 and 05 narrows it down to those cylinders.

Clean throttle body and MAF, you may have carbon flaking off and fouling plugs. You could try taking it for a good thrash down the highway for an hour.

Trouble shooting a misfire, Code P0300, P0301 ... - YouTube

? 23:39
www.youtube.com/watch?v=G_grIaTgdRI
Oct 26, 2013 - Uploaded by Robert DIY For the new play by play misfire video click here: ... Trouble shooting a misfire, Code P0300, P0301, P0302, P0303, P0304, P0305, P0306, ...

P0301 is a misfire in cylinder 1. This can be a lot of different things, but it seems you've already been throwing parts at it. I would recommend a compression test to test for a leaking gasket or a bad piston ring or valve.

I think you have an engine wiring harness issue going on here.

check the coil, Normally when that code comes up its followed by more, as in P0301 02 03 , which would indicate which cylinder is being effected, P0300 Random/Multiple Cylinder Misfire Detected is what the code means and any of these could effect that code being thrown

• 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

The only thing left would be fuel. Check fuel pressure , replace the fuel filter, and check the injectors(ohm's from 11 to 15) and the injector harness. Mostly on the harness make sure you didnt pinch a wire putting it back together, especially the map and coolant wires.

P0300 - Random / Multiple Cylinder Misfire Detected

Possible Causes:
- Improper spark plug
- Insufficient compression
- Incorrect fuel pressure
- The injector circuit is open or shorted
- Fuel injectors may be faulty
- Intake air leak

Possible Solutions:
- Perform Injector Service
- Replaced Spark Plugs
- Replaced Injectors
- Replaced Ignition Coils

P0301- Cylinder Number 1 Misfire Detected

Possible Causes:
- Improper spark plug at cylinder #1
- Insufficient compression at cylinder #1
- Incorrect fuel pressure
- The injector circuit is open or shorted at cylinder #1
- Fuel injector #1 may be faulty
- Intake air leak at cylinder

Possible Solutions:
- Perform Injector Service
- Replaced Spark Plug #1
- Replaced Injector #1
- Replaced Ignition Coil #1

Most likely your issue is with cylinder number 1. Follow the info I have provided and you should be able to solve this issue.

P0300 indicates that there is multiple miss fire in the ignition system. P0303 and p0304 indicates the miss fire is in cylinder #3 and #4. Replace the spark plug, and wire set, and rotor and cap if there is one. Can not remember if there are coil packs on the civic, the age thing. change the fuel filter and clean out the fuel injectors with fuel injector cleaner for the next 3 full ups. When the spark plugs are removed, inspect them for condition, if there clean or dirty with carbon build up. which would indicate how the engine is running. Keep me posted and drive safe.

take sample of your fuel into clear plastic bottle from fuel line
is there any water present?
this can cause these codes and then not go on storing codes for other bank even though that bank will be missfiring also due to water & P0300 Random/Multiple Cylinder Misfire Detected being logged
check all connections to coils/leads & wiring connectors
due to miss fire codes for cyl 1,3,5 all on the same bank
also look and check for air leaks on that bank (hose knocked off or splithose)inlet manifold gasket,brake booster etc...
3 injectors being blocked slightly on same bank posible!!!
check wires and signal

was it running like this b4 tune up & repairs?
this is what codes are
P0170 Fuel Trim Malfunction (Bank 1)
P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0305 Cylinder 5 Misfire Detected

the last code is for trans due to misfire/running lean on bank 1 probably a torque problem code

cylinder 1 misfire and low compression. Plugs and wires changed plus new fuel injectors. The engines still misses and no one can find the cause. When put on the computer it read misfire cylinder 1.