Engine misfire on cilynders 2&3. I r&r coil pack and same problem. I have good compression at about 160psi, I checked injectors and spark plugs as well, all good, I need help. Possibly ignition module?

The fuel injector and compression need verification .

injector or valve train

Recheck all work you have done. Sometimes folks replace the wrong coil pack as they can be easily confusing. If everything seems ok, there are still two possibilities. First, ensure that the fuel injector is consistently firing for the cylinder, and also ensure that it is not constantly firing. Either can cause a misfire, one for too little fuel, one for too much fuel. Lastly, check compression in the suspect cylinder. A broken or burnt valve can cause loss of compression, leading to misfires.

P0304 is engine misfire #4 cylinder Several things can cause a misfire #1 electrical which you have covered #2 Mechanical Test engine compression is should be around 150 cranking and 120 running . internal valve train components can cause bad compression and the valves then self. #3 fuel injector can be the cause suggest swapping with a know good cylinder and see if misfire follows injector.

It just can't do that. No way to shut down one side of an engine.
Misfires are caused by lack of fuel, spark, or compression. One of the three is missing. One whole side-that rules out spark. Coil pack design just won't affect one side of the engine. That leaves fuel or compression. Some multi-port injection systems are so-called "bank fired" -that is, one side or bank of the engine will pulse the injectors at the same time, first one bank, then the other. But in the early '90's, some cars came out with sequential fuel injection, which pulses the injectors individually, following the firing order of the cylinders, more precise fuel metering that way. I would have thought that an Avalon would be sequential injection, but you could check. Anyway, you need to check if the injectors are working on 2, 4, & 6. The power wire to all injector systems is a single wire that is spliced to each injector. Conceivably, the splice to that bank or side may have broken. With key on, every injector should have voltage at the injector connector. Only two wires to each injector- a power wire and a ground wire. If no power on 2, 4, or 6-that is probably it. (On bank fired injection, all three ground wires on each side splice together before the ground wire goes into the computer. With sequential, each injector ground wire goes to the computer separately.)
Beyond fuel, it is possible that the fuel/air mixture is being affected on only one side. If you have a noisy exhaust leak on that side, it could lean out the mixture.
Finally, low compression will cause a misfire. Possibly, a camshaft on that side is not in time. Only way to check is to do an engine compression test.

That sounds like your coil pack. The coil to number 1 & 4 may be bad. The other coil, to number 2 & 3 cylinder is good and working.
If it's not the coil, you may have to check the wiring to the coil pack-something is amiss. You could swap the coils around and see if the misfire follows your switch to 2 and 3...
If the above don't get no good results, it's not an ignition problem, then you will need to check compression on number one cylinder. Look for any mechanical problem from low compression. 3 major causes of misfires: gas, spark, or compression.

Hi, the first step I recommend is to check for spark. You can do this by starting the car and then carefully pulling up the boot to the #1 ignition wire at the coil. If sparks are jumping inside the boot, you have spark and the ignition system is working.

1. Ignition: If there is no spark, shut of the engine and use an ohmmeter to check the impedance of the coil. Take the boot off, and connect your ohmmeter from the coil terminal to the engine ground. The resistance should be around 10-20 kohms. If not, replace the coil. If yes, the problem is the ignition module under the coil.

Now, assuming you have spark (which I believe you do, because the coil runs 2 cylinders, and you only have one cylinder that is misfiring), the problem will be a lack of compression or a bad injector (or possibly the injector wiring).

Note: I will provide repair steps once the troubleshooting is complete and the problem identified.
Also, if you do not have a multimeter, you can get one for $10-20 at radio shack or even Walmart. It will save you money overall--or maybe you have a friend that you could borrow a meter from.

2. Injector: The next easiest test to run is to see if the injector solenoid is clicking. You can do this by holding a long screwdriver to the injector and hold the other end of the screwdriver to your ear. With the engine running, you should hear the injector clicking. If not, you have a bad injector or a wiring problem. To determine whether the problem is the injector or the wiring, pull the connector off the injector and measure the AC voltage in the connector with the engine running. The voltage should be 1-2 volts or similar to that voltage of any other injector connector.
If the voltage is good, but the injector is not clicking, replace the injector.

3. Valves/compression: the last possible reason for a misfire is a lack of compression. The intake valve must open to accept a fuel/air charge, and both valves must be closed for the cylinder to fire. Sometimes an exhaust valve will burn and not hold compression. A blown head gasket can also cause this problem. The test we use to check the valves is a compression test. You can borrow or purchase a compression tester if you get to this point. Remove a few of the spark plugs including the cylinder that is misfiring. Screw the compression tester into the spark plug hole and crank the engine for a few revolutions. Record the pressure on the gauge, release the pressure, and go on to the next cylinder. If the pressure is much lower on any cylinder as compared to the highest cylinder, the cylinder head will have to be removed to correct the issue.

Please let me know the results of your troubleshooting and feel free to ask questions as you go.

A code P0303 (misfire #3 cyl) may mean that one or more of the following has happened:
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

Possible Solutions:
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.


Keep us updated.

Check for power at the injector. Possibly plugged, replace.

Random misfires are usually caused by a leaking vaccum pipe, and will only be apparent at idle and sometimes at low engine speeds under part throttle.
Isolated misfires are usually caused by a faulty injector, coil pack, ignition lead, or low compression.

Well, you're going to have to check the spark plug,  spark plug wire, the coil pack, low compression, and the ignition lead, which only really leaves the injector, or even an intake leak at the offending cylinder. 

Start the engine and then spray intake spray or the like around the intake at the offending cylinder and see if the engine note changes. If it does, then you have an intake leak, otherwise, they need to check the injector in the offending cylinder. 

Good luck and hope this helps. It might just be time for a tune up: new spark plugs and wire or some fuel injector cleaner every fill up for now.