[Kitsuki eclipse]

I have code p0303 and it's not misfire the cylinder isn't firing at all it has fuel spark air and compression we know it has spark because my friend was stupid enough to touch the end of the wire while it was running and we know the spark plug is good because when we took it out we put it in cylinder 5 and it was working fire(when we pulled the spark plug the first time there was no carbon on it at all and was brand new) we also know it's getting spark because we can hear the injector working but it not firing and we can't figure out why also we did a compression test in the 3 front cylinders and they all came back 120 psi

 

[jelazar]

It sounds like you're checking the front head, but those are cylinders 2/4/6. Cylinder #3 is on the rear head, near the firewall.

 

[Kitsuki eclipse]

Is it? Everything I've been looking at online is always saying saying one thing then another person will say something different thank you for the input

 

[Kitsuki eclipse]

It sounds like you're checking the front head, but those are cylinders 2/4/6. Cylinder #3 is on the rear head, near the firewall.

That still begs the question why was there no carbon on that spark plug

 

[WhiteSpyder]

Plugged injector ? Hummm. That is a question, not a statement of fact. ...J.D.

 

[Kitsuki eclipse]

Plugged injector ? Hummm. That is a question, not a statement of fact. ...J.D.

How would I go about checking that

 

[WhiteSpyder]

Not sure other than change it out and see if it goes away. What I am not sure of is how the ECU generates the P0303 code. Will a lean misfire on #3 trigger it ? Or does it have to see an electronic misfire in the ignition system to trigger that code? ...J.D.

 

[jelazar]

Is it? Everything I've been looking at online is always saying saying one thing then another person will say something different thank you for the input

It can be confusing and Mitsubishi doesn't make it easy because sometimes the factory service manual says bank 1 and bank 2, and sometimes right bank and left bank. These are all pics from the factory service manual. If you piece it together:

Bank 1 = right bank = the bank by the firewall = cylinders 1/3/5
Bank 2 = left bank = bank by the radiator = cylinders 2/4/6

 

[jelazar]

Not sure other than change it out and see if it goes away. What I am not sure of is how the ECU generates the P0303 code. Will a lean misfire on #3 trigger it ? Or does it have to see an electronic misfire in the ignition system to trigger that code? ...J.D.

A faulty injector will cause a P030x code, even if the ignition firing signal is normal. The ECU watches the crankshaft position sensor waveform and notices a deceleration when it's that cylinder's turn to push, whatever the reason (no ignition, no fuel, no compression/detonation, etc.). The ECU will set the code if there's a misfire more than 2% of the time on a given cylinder.

 

[jelazar]

How would I go about checking that

Get an injector noid light and an electrical multitester. Remove the electrical connector on the #3 injector and use a multimeter to test the resistance of the injector (not the injector harness). The injector should be 16-18 ohms resistance. If the resistance is way off, replace the injector.

If the injector resistance checks good, connect the noid light to the injector harness and make sure there isn't a problem with the injector harness. If the noid light shows the harness is good, swap the #3 injector with another cylinder and see if the malfunction moves to the other cylinder. (I'd pick a front cylinder because it's easier to access.)

You have to remove the intake plenum to do all this. While you've got the intake plenum off, I'd also check compression on the #3 cylinder and I'd re-verify you've got a good spark on the #3 plug. If in doubt, I'd replace the plug, cable, distributor cap, and rotor. It's a pain to R&R the plenum and it's another chance to break something, so I try to combine work when I take it off.

 

[WhiteSpyder]

I also did not see where he has done anything to the ignition. Having enough spark to get a shock off the ignition wire does necessarily not mean there is a clean enough spark to assure the engine will not misfire. If not already checked, I would look at the cap, rotor, and wires. These are usually the most common cause of misfiring in any engine. ...J.D.

 

[Kitsuki eclipse]

I also did not see where he has done anything to the ignition. Having enough spark to get a shock off the ignition wire does necessarily not mean there is a clean enough spark to assure the engine will not misfire. If not already checked, I would look at the cap, rotor, and wires. These are usually the most common cause of misfiring in any engine. ...J.D.

The cap rotor and wires were replaced already

 

[Kitsuki eclipse]

Get an injector noid light and an electrical multitester. Remove the electrical connector on the #3 injector and use a multimeter to test the resistance of the injector (not the injector harness). The injector should be 16-18 ohms resistance. If the resistance is way off, replace the injector.

If the injector resistance checks good, connect the noid light to the injector harness and make sure there isn't a problem with the injector harness. If the noid light shows the harness is good, swap the #3 injector with another cylinder and see if the malfunction moves to the other cylinder. (I'd pick a front cylinder because it's easier to access.)

You have to remove the intake plenum to do all this. While you've got the intake plenum off, I'd also check compression on the #3 cylinder and I'd re-verify you've got a good spark on the #3 plug. If in doubt, I'd replace the plug, cable, distributor cap, and rotor. It's a pain to R&R the plenum and it's another chance to break something, so I try to combine work when I take it off.

I'll work on this whenever I get some free time I've gotten decent at taking the manifold off as I had to do it alot in my other eclipse

 

[WhiteSpyder]

The noid light will only indicate if the solenoid on the injector is firing. I think you probably already knew that if you could hear the injector clicking. What the noid light does NOT tell you is if the injector nozzle is partially or fully plugged. In the old days we could read lean misfire on an oscilloscope by reading the wave pattern, but this type of thing is no longer in use. I did a lot of this kind of diagnostics way back when. ...J.D.

 

[Kitsuki eclipse]

The noid light will only indicate if the solenoid on the injector is firing. I think you probably already knew that if you could hear the injector clicking. What the noid light does NOT tell you is if the injector nozzle is partially or fully plugged. In the old days we could read lean misfire on an oscilloscope by reading the wave pattern, but this type of thing is no longer in use. I did a lot of this kind of diagnostics way back when. ...J.D.

So basically a big guessing game at this point

 

[WhiteSpyder]

So basically a big guessing game at this point

It is always a guessing game until you can verify what is going on. Just the nature of diagnostics. The other option is to keep throwing parts at it until something sticks. That gets expensive fast. ...J.D.

 

[jelazar]

So basically a big guessing game at this point

No, not at all! It's almost certainly either ignition, fuel injection, or compression. You can methodically test each one until you get to the answer. If you eliminate all those things we can start thinking about wacky "what ifs", but for know concentrate on the common things.

 

[WhiteSpyder]

Thinking about it, the noid light only tells you there is an injector pulse from the I/O port on the ECU up to the injector. It does not say what the injector's condition is. The solenoid on the injector could have an open winding and it would still light. I imagine if the solenoid were shorted it wouldn't light. I use the "click" test first to see if I can hear anything. You might just buy one injector and replace it. It is pretty hard to visually see if an injector is plugged. ...J.D.

 

[jelazar]

Thinking about it, the noid light only tells you there is an injector pulse from the I/O port on the ECU up to the injector. It does not say what the injector's condition is. The solenoid on the injector could have an open winding and it would still light. I imagine if the solenoid were shorted it wouldn't light. I use the "click" test first to see if I can hear anything. You might just buy one injector and replace it. It is pretty hard to visually see if an injector is plugged. ...J.D.

Correct: you have to check both the injector and it's harness. That's why you check the resistance on the injector and replace it if it's obviously bad. Otherwise swap it for another location. Then if the fault follows to the new cylinder, you know it's the injector and decide whether to clean or replace. The injector noid light only tells you whether there's signal from ECU to the injector. And you still need to check compression, and spark plug and wire.

 

[Sisyphus58]

Theoretically, the injectors should last way longer than the plugs, but if you have more than 100k on the injectors, I personally would replace them all. If one goes bad or gets too clogged, it's just a matter of time before the others follow.

Try throwing in some injector cleaner in your fuel tank at a slightly higher concentration than suggested on the label and take it on the highway for some full throttle bursts. At the very least, this will help clean the injectors which are working properly, and if the misfiring in #3 goes away, that tells you it was partially clogged. However, I would consider this only a temporary fix until you can afford to replace all the injectors.
There are other, more complicated and more effective methods to clean injectors, but you never really know for sure how clean you are getting them. If you keep a car long enough, you should expect to have to replace the injectors eventually, and preferably all at once depending on how involved a task it is to do.