P0302 & Rough Idle

[mharrison]

I have a 97 Eclipse 2.0 Non-Turbo 5 speed.

I'm getting a P0302 (misfire Cylinder 2) CEL and a rough Idle. I swapped plugs, replaced wires, swapped wires, etc. to rule out the plugs and wires. The problem always stayed on cylinder 2. The head was reworked about 5k miles ago. I verified that compression is still good on all 4 holes.

It idles rough, but runs OK at anything above around 2K RPM's (approximately, it varies). This lead me to believe that it was the EGR valve stuck open. I verified that the EGR valve is working correctly. (Or at the very least, not stuck open.)

My next thoughts are bad injector or Idle Air Controller (IAC). (Oh, I also intend to borrow a friends Coil to be sure mine is OK.)

What do you guys think? Am I on the right track or should I be going elsewhere?

 

[Dark DSM]

I have a 97 Eclipse 2.0 Non-Turbo 5 speed.

I'm getting a P0302 (misfire Cylinder 2) CEL and a rough Idle. I swapped plugs, replaced wires, swapped wires, etc. to rule out the plugs and wires. The problem always stayed on cylinder 2. The head was reworked about 5k miles ago. I verified that compression is still good on all 4 holes.

It idles rough, but runs OK at anything above around 2K RPM's (approximately, it varies). This lead me to believe that it was the EGR valve stuck open. I verified that the EGR valve is working correctly. (Or at the very least, not stuck open.)

My next thoughts are bad injector or Idle Air Controller (IAC). (Oh, I also intend to borrow a friends Coil to be sure mine is OK.)

What do you guys think? Am I on the right track or should I be going elsewhere?

None of those things you suggested would normaly cause a cylinder misfire. But the one thing you did mention about the coil would normaly be the first place i would have started along with plug and wire. Now if that doesnt correct your problem, i would start looking at harness wires, then your ECU. Other than that there couldnt possibly be anything else to cause your misfire. And of course this is assuming that the compression across all cylinders are within proper specs. Now i could be wrong as alot of people on here like to prove that there better, but hey at least im offering my opinion.

 

[mharrison]

Oh, I need to add that this isn't a dead miss. Pulling the plug wire off of cylinder two causes a similar power loss as pulling any of the others. That's why I'm thinking that the cylinder 2 misfire might be a false error being brought on by another component, such as an EGR dumping the exhaust closer to cylinder 2 than the others etc....

I did notice however that the EGR dumps exhaust in just behind the throttle body, so if anything I'd expect to see problems caused by that on cylinder 4.

At any rate, I'm planning to swap out the coil with a known working one next to see if that will resolve the issue.

 

[95 'clipse RS]

here are a few things that could cause your problem. spark plugs worn or not gapped properly, spark plug(s) fouled, plug wires damaged or shorted, weak or faulty iginition system, vacuum leaks, and uneven or low compression. hope this helps

 

[mharrison]

here are a few things that could cause your problem. spark plugs worn or not gapped properly, spark plug(s) fouled, plug wires damaged or shorted, weak or faulty iginition system, vacuum leaks, and uneven or low compression. hope this helps

1. Well, the plugs are good, not fouled, and are gapped properly, and have been swapped around to verify.
2. The plug wires have been ruled out as they were replaced as well as swapped around.
3. I haven't been able to find any vacuum leaks.
4. The compression is 206-210 on all 4 cylinders.

So, I guess that leaves ignition system components.

A faulty injector couldn't generate a misfire code? I would assume that a misfire code is generated by a downstream 02 sensor or something similar detecting a fuel/air mix that hasn't been completely burned. I could see theoretically how an incorrect amount of fuel due to a bad injector could cause this condition if that is how the code is generated. Any comments?

 

[4UH8ERS]

1. 
   So, I guess that leaves ignition system components.
   
   A faulty injector couldn't generate a misfire code? I would assume that a misfire code is generated by a downstream 02 sensor or something similar detecting a fuel/air mix that hasn't been completely burned. I could see theoretically how an incorrect amount of fuel due to a bad injector could cause this condition if that is how the code is generated. Any comments?

1. 
   
   The downstream o2 sensor does not make a/f readings or adjustments. It simply detects the condition of the catalytic converter and will let you know if its flowing sufficiently.
   The upstream o2 sensor takes a/f ratio readings and makes proper adjustments by sending readings to the ECU.
   
   I had a P0302 code that read misfire in cylinder 2 and it ended up bieng my CAS (crank angle sensor), but my car would completely die. I would in your case start by replacing the coil then go to other areas if that was not the culprit. (i.e. CAS, upstream o2 sensor, ignition circuit, timing, fuel pressure)

 

[ClevelandDSM]

^^^ Like said above, Check your coil to make sure it is showing its full reading. Then check your sensors and along the fire wall where the wiring harness runs to make sure there is not anything funky going on. Also there is a relay cluster under the hood, check the fuel relay just to make sure nothing there is bugging out. I had an issue with a eclipse a couple years ago, where the relay would stick after the car came off my lift, and it would for some reason only feed fuel to 2 cylinders. tapping on it with a screw driver handle stoped this problem.

 

[95 'clipse RS]

you might wanna check some information sensors if you think that its a/f ratio related. some information sensors are, cam pos sensor, crank pos sensor, engine coolant temp sensor (ECT) (not the sending unit), intake air temp sensor, knock sensor, MAP sensor, upstream O2 sensor as mentioned (located on downpipe), Throttle pos sensor, and vehicle speed sensor (VSS).

also you could check the cam angle sensor, this tells the injectors when to spray fuel. simple check you could unplug it after its running, and it should work in the open loop function, where the injectors are constantly spraying fuel. but if it makes no difference in the idle you might have found your problem. just an easy check to rule that out.

if you want to check the sensor itself, you can disconnect the plug wires from the coil pack, then with the connector attached to the sensor, use a voltmeter and back probe the signal wire and the ground wire, then crank the engine. the voltmeter should fluctuate from about .4 to 3 volts. this will verify that you'll need to replace the cam sensor or not. just thought id throw it out there just in case.

you can also ohm out the iginition coil and check if its good also, which i would rather do than swapping it out. to do this check the primary resistance, which is 1 and 4 on the coil, the resistance should be .51 to .61 ohms, then test the secondary, 2 and 3, this should be 11,300 to 15,300 ohms. if its out of spec replace it.

note, be sure while using volt and ohm meters to set it to the correct setting, just so you dont blow it up. i have to admit, ive accidentally done it before. hope this helps ya out man.

oh, also, after the car has been running a bit, try taking out the plug on cylinder 2 and looking it over, sometimes this can tell you exactly how your engine is running on that cylinder. compare it to the others, and you might also wanna try this, when the engine is coldish, like run it for two min. check it, then a few more, then let it warm up fully.

 

[Locke]

I would assume that a misfire code is generated by a downstream 02 sensor or something similar detecting a fuel/air mix that hasn't been completely burned.

The ECU uses a combination of knock sensor and CKP inputs, and compares them to a schedule to determine if a misfire has occurred, and on which cylinder. I wouldn't trust it 100% though.


Why I don't trust misfire codes;

One of our other vehicles threw a misfire code every time we hit a jarring bump on the highway. Many, many inconvenient trips for warranty work before they determined the likely cause being a slight throttle fluctuation happening with the bump, and the knock sensor registering the impact. Their novel solution was to reprogram the ECU, slightly desensitizing the knock sensor. Problem solved.

 

[4UH8ERS]

Also there is a relay cluster under the hood, check the fuel relay just to make sure nothing there is bugging out. I had an issue with a eclipse a couple years ago, where the relay would stick after the car came off my lift, and it would for some reason only feed fuel to 2 cylinders. tapping on it with a screw driver handle stoped this problem.

The relay he is talking about is the ASD relays located on the drivers side firewall.

 

[mharrison]

OK, the coil checked OK with a meter and was even replaced with a known good one with no change. (Borrowed one from a friend.)

I unplugged and replugged the relays and they appear OK, tapping them while idling made no difference in the miss.

I'm still thinking a failing/clogged fuel injector. I guess I'll meter those and tear them down next.

I've got to check with my FLAPS and see if they have loaner NOID lights to test the fuel harness.

 

[mharrison]

Well all four injectors are clicking while running based on the screwdriver to the ear method. The resistance meters in the OK range. I'm still thinking #2 is bad or clogged. I pulled the fuel rail and all 4 injectors today. I was going to swap two of the injectors and see if the misfire code changed, but pulling it was such a PITA I'm putting a new one in. I don't want to go through this again! .

Anyway, I also pulled the throttle body to help get at the fuel rail mounting bolts (they are a complete PITA). The TB was NASTY inside. I cleaned it out really well and that can't do anything but help!

My new injector is supposed to be at the FLAPS tomorrow and should be installed any running by the end of the day. Hopefully this will resolve the problem.

 

[mharrison]

OK, I've replaced the #2 injector and replaced the fuel filter. (The filter was due anyway.) It appears that my problem is still here.

Do you guys have any other suggestions? I think the only other one I've heard was the Cam Position Sensor...