misfires, no CEL, no codes

[royboy15931]

On a 97 420a eclipse, the engine will misfire and misfires. But this doesn't produce any CEL, any check engine light, or any code or any codes. That's right! NO CELs, no check engine, and no codes.
Has anyone seen this before?
I can probably find the misfire cause but aren't OBDII system suppose to light up the CHECK ENGINE LIGHT when an engine misfires?

[EclipseRST]

Yeah... You probably need new plugs, maybe some plug wires or even a coil pack! A misfire could be a lot of things, not something a computer has control of could be one, like the plugs or plug wires. I suggest getting a new set of each. If that doesnt help test the coil, dont automatically think its the ECU when your engine misfires. Yes the CEL comes on when the computer senses something is wrong. The computer cant sense bad plugs or wires!

[1stGenRocks]

usually the computer will notice the misfire though. does the light come on with the key on and the engine off? if it doesnt come on then you have a bad CEL bulb or someone unplugged it.

[royboy15931]

Hey Jake-----
Nice crankwalk!

Hey 'rocks----
Yes. The CEL comes on with KOEO and it came on when I had an evap system leak. But the misfires don't light it up.

[EclipseRST]

Originally Posted by 1stGenRocks

usually the computer will notice the misfire though. does the light come on with the key on and the engine off? if it doesnt come on then you have a bad CEL bulb or someone unplugged it.

The computer is not going to tell if the misfire happens after the coil pack! If you think it will, go outside right now, pull off one of the spark plug wires while your car is running... How is the ECU going to see that? There is no sensors hooked to the spark plug or spark plug wires. There for if you are getting a misfire and you have no CEL, then it is usually in the spark plug wires or spark plugs itself. I have never had a CEL come on and tell me I have a bad spark plug wire... I wish it would, make life a whole hell of a lot easier, but it doesnt. Same goes with spark plugs. If you had a CEL for misfire it would be for something the ECU's could see, like the coil pack.



Roy... Yeah a lot of people like that, luckily I have yet to get it! (knock on wood)

[1stGenRocks]

hey jake. ui know the computer doesnt have any sensors on the spark plugs. but i work as a mechainc and i have seen many misfire codes caused by bad plugs/wires. the computer notices the knock or the loss of power.

[Killa_DSM]

I was misfiring like a weak ago, i changed the plug wires and it fixed the problem. Does it miss under WOT? Thats what mine did.

[scottsee]

last time i had that problem was when i pressure washed my engine and got water down in the plugs and up into the wires. had to take them all off and use an air compressor to blow all the water out.

[royboy15931]

Hey Ragin---When I try WOT it seems to go into limp in mode. But still no CEL or P0300. Did you get a CEL or DTC with your misfires?

Hey 'Rocks---Have you ever worked on misfires without seeing any codes?

Hey Scott---Haven't washed her. Too cold out there now.

[Killa_DSM]

Originally Posted by royboy15931

Hey Ragin---When I try WOT it seems to go into limp in mode. But still no CEL or P0300. Did you get a CEL or DTC with your misfires?

I never got a CEL even though i was missing.

[EclipseRST]

Originally Posted by RaginAsian

I never got a CEL even though i was missing.

Exactly like I said... You will not get a CEL with bad plugs or plug wires.

Originally Posted by 1stGenRocks

hey jake. ui know the computer doesnt have any sensors on the spark plugs. but i work as a mechainc and i have seen many misfire codes caused by bad plugs/wires. the computer notices the knock or the loss of power.

Rob - If you got a Misfire code it was not from bad plugs or wires... something else was causing a misfire! There had to be something before the coil pack that wasnt allowing it to get the right amount of power for it to put out enough voltage to create a spark, then when the computer notices this it throws the CEL. The computer will not throw a misfire code if there is a loss in power and the knock sensor was going crazy. Another thing, 420a motors do not have knock sensors... So the only thing would be a loss in power and how would the computer sense that? If you got a CEL from loss in power, you would get one everytime you slow down cause when you push the break, push in the clutch, let the RPMs drop you are loosing power! I know what I am talking about so stop trying to argue.

Roy - Is there a reason you dont take my advice? I know the 420a inside out probably better than anyone on this site! What makes you think I dont know what I am talking about?

No CEL and misfire it has to be the coil pack or after that, you could be getting plenty of power to your coil pack but yet is bad and the computer cannot sense that. I would start with spark plugs (GAPPED CORRECTLY!!) and then spark plug wires! If you still have a misfire once you replace the plugs, then get wires, if you still have a misfire then see if you can find a coil pack or even have yours tested. If and when you do all that but you still have a misfire then come back here and let us know everything you did.

Until then, if you dont want to take suggestions then why are you here? We are all here to help eachother you should atleast listen to everyone's suggestion or tips. If you dont like their ideas ask questions or tell them why you think they are wrong, dont just blow them off cause 75% of the time people know what they are talking about on here!!

[royboy15931]

First of all--THANKS to everyone for helping with this no code problem.

Originally Posted by EclipseRST

Exactly like I said... You will not get a CEL with bad plugs or plug wires.



Rob - If you got a Misfire code it was not from bad plugs or wires... something else was causing a misfire! There had to be something before the coil pack that wasnt allowing it to get the right amount of power for it to put out enough voltage to create a spark, then when the computer notices this it throws the CEL. The computer will not throw a misfire code if there is a loss in power and the knock sensor was going crazy. Another thing, 420a motors do not have knock sensors... So the only thing would be a loss in power and how would the computer sense that? If you got a CEL from loss in power, you would get one everytime you slow down cause when you push the break, push in the clutch, let the RPMs drop you are loosing power! I know what I am talking about so stop trying to argue.

The knock sensor on the 420a is located under the intake manifold. Go out and take a look. The computer senses power loss by way of the crankshaft sensor. Check this in the manual or ask a mechanic.

Roy - Is there a reason you dont take my advice? I know the 420a inside out probably better than anyone on this site! What makes you think I dont know what I am talking about?

See above. That's why I don't take your advice.

No CEL and misfire it has to be the coil pack or after that, you could be getting plenty of power to your coil pack but yet is bad and the computer cannot sense that. I would start with spark plugs (GAPPED CORRECTLY!!) and then spark plug wires! If you still have a misfire once you replace the plugs, then get wires, if you still have a misfire then see if you can find a coil pack or even have yours tested. If and when you do all that but you still have a misfire then come back here and let us know everything you did.

Until then, if you dont want to take suggestions then why are you here? We are all here to help eachother you should atleast listen to everyone's suggestion or tips. If you dont like their ideas ask questions or tell them why you think they are wrong, dont just blow them off cause 75% of the time people know what they are talking about on here!!

After reading the SUGGESTIONS on this thread, I figured I'd first try replacing the wires tommorow. That worked for Ragin'.
On my way to pick up wires, I filled her up with gas.
Hadn't gone more than a mile further and the misfires just STOPPED!
I remember now my misfires started a bit after my last fill-up.
I apparently got a tank of crappy gas. I know there aren't any codes for crappy gas but I still wonder why the misfires didn't cause a code!

[Killa_DSM]

I'm not trying to start shit but, if Jake (EclipseRST) says something about a car, it is most likely true. Their are many members on this site that knows what their talking about. He is a very respectable tuner and knows his cars. So if he suggests something i would definitly take it in consideration.

[EclipseRST]

Originally Posted by royboy15931

The knock sensor on the 420a is located under the intake manifold. Go out and take a look. The computer senses power loss by way of the crankshaft sensor.

Wrong. That is the crank position sensor! Why dont you go out and look at it once. Take it out... Examine it. On a 4g63 motor, yes the knock sensor is under the intake manifold. NOT ON A 420A! Damn whats so hard to understand about that.

Also the computer will not sense power loss by the crank sensor.. Explain to me how it does? The crank speed varies so there for everytime the RPM's drop, you stop your car, you shut off the car the ECU would throw a code!

Oh and by the way, I am a certified mechanic... So if your mechanic knows all about this motor or you do, WHY IS IT MISFIRING? Exactly you came here for a reason and I hate n00bies that tell me that I do not know what I am talking about.

[royboy15931]

I don't want you to lose your certification so I'll take a minute to explain this to you.

Originally Posted by EclipseRST

Wrong. That is the crank position sensor! Why dont you go out and look at it once. Take it out... Examine it. On a 4g63 motor, yes the knock sensor is under the intake manifold. NOT ON A 420A! Damn whats so hard to understand about that.

On the 420a the crank position sensor is down lower than the knock sensor. It's right above the oil filter. The KNOCK sensor is right where I said before. You should be able to verify this in the Eclipse Sevice Manual in the section on Engines. For those without a manual, this DSM web page describes the entire 420a engine including the KNOCK sensor.
http://www.sjdsm.com/mods/2gntpwrtrn.htm
And you don't have to "take it out" to examine it. You can just order one from CarParts.com at this web page:
http://www.carparts.com/cgi-bin/sews...m+jcw-carparts
Just enter in 1997, mitsubishi,knock sensor,eclipse to see the 420a knock sensor, part #144-602. ( I assume you know that VIN:Y is the 420a engine)

Oh and by the way, I am a certified mechanic... So if your mechanic knows all about this motor or you do, WHY IS IT MISFIRING? Exactly you came here for a reason and I hate n00bies that tell me that I do not know what I am talking about.

If you paid attention to my previous post , you'd know we do know why it was misfiring. So I'll leave you to go on hating n00bies.

Thanks again to all who provided feedback so I've learned that misfires can occur with codes and can occur without codes.
I've got to move on to other forums but I might be back.