Boss 302 - Misfires (codes p0300, p0304, p0307, p0420 & p0430

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

2000 Toyota Corolla, P0171 & P0420 codes - YouTube

? 5:43
https://www.youtube.com/watch?v=ahJnJ19-vwY
Jun 13, 2011 - Uploaded by StandardBrandParts
Standard Motor Products presents: Technician's Toolbox "2000Toyota Corolla, P0171 & P0420 codes"

Smoke testing for codes P0171 P0174 - YouTube

? 5:48
https://www.youtube.com/watch?v=kZsqEfP-5zM
Jan 18, 2011 - Uploaded by realfixesrealfast
These two codes mean a V style engine is running lean on both banks. So you have to be thinking - what can ...

How to repair fault code P0171 and reset warning light ...

? 26:31
https://www.youtube.com/watch?v=Y8FBGrCT3rM
Nov 27, 2014 - Uploaded by Peter Finn
How to repair and fix fault or error code P0171 and reset warning light Toyota Corolla VVT-i engine. ... Also how to find fault codeusing OBD scanner. ... Trouble shooting a misfire, Code P0300, P0301, P0302, P0303, P0304, P0305, P0306, ... 2000 Toyota Corolla, P0171 & P0420 codes - Duration: 5:43. by ...

P0300 = Random/multiple cylinder(s) - misfire detected.
P0302 = Cylinder 2 - misfire detected.
P0304 = Cylinder 4 - misfire detected.
P0306 = Cylinder 6 - misfire detected.

A misfire can be caused by a few things. The most common causes are usually spark supply or fuel supply. Get BOTH of these checked.
All the misfires are on the same side of the engine so I would suspect a fuel rail or an injector issue on that side of the engine.

check the coil if coil is ok spark plug if there are ok may damage in emission valve or injectors code relate it to the problems are p0300 p0301 p0302 p0303 p0304 p0305 p0306 p0307 p0308

check engine light on, code P0300 P0301 P0302 P0303 P0304 THIS ARE ALL MISFIRES, 300 is random, 301 cylinder one 302 cylinder 2 and so on, the evaluation is once apart check the spark plugs condition, if they look ok, replace coils and plugs. if the light is not on, verify it works by turning the ignition to pos 2, if not replace light, if yes, and this here are not the codes, read the codes and re send it, posible bad cylinders, or poor injector.

P0300 - Random multiple cylinder misfire
P0301 , 302 and 304 - Cyliners 1, 2 and 4 misfire
P0351 - Ignition coil A primary/secondary circuit malfunction
P0354 - Ignition coil D primary/secondary circuit malfunction

I have a 2004 LS V8

There all bad by now

Replace all the OEM Coils that are left

P0171 is a lean oxygen sensor code. Codes P0300, P0302 and P0304 are all cylinder misfire codes. Low fuel pressure can cause all of these codes and would be the first thing I would check before replacing anything. Lean codes can be caused by misfiring cylinders. Engines running lean can cause misfires. So you have to figure out which came first - the lean condition or the misfire. Also, it needs to be verified that the engine actually is running lean and the oxygen sensor is not "lying" to the computer. An oxygen sensor that is a liar can actually cause the engine to run rich while telling the computer that it is running lean...AND THIS can cause misfires.

P0420 Is an evaporative emissions system leak code. This code is most often caused by a bad or loose fuel cap. It is also often caused by people refueling their vehicles with the engine running. It can also be caused by a leak in the system that has nothing to do with the fuel cap or refueling.

Evaporative Emissions Vent Solenoid failures are very common on Toyotas and can also cause P0420.

So, to wrap all of this up in simple terms:
You need to get some diagnostics done to save you from wasting a bunch of your hard-earned cash trying to guess what to do to fix the car.

well the codes
p0300 multiple misfire
p0303 misfire cylinder 3
p0304 misfire cylinder 4
p0307 misfire cylinder 7

can be alot of things check cylinders for compression is what i would do first..

Here is a good site for OBD II trouble codes.  P0300: Random/Multiple Cylinder Misfires Detected, P0301: Cylinder 1 Misfire Detected, P0304: Cylinder 4 Misfire Detected.