Intermittent miss on a IX...advice???
Apr 17, 2008, 06:39 PM
#1
Intermittent miss on a IX...advice???
Okay heres the deal. The car is a IX MR (car is my sig). I can't seem to pinpoint this problem. Been to the dealer (fixed injector seals didn't help) and personally have a good chunk of experience with these cars but I'm puzzled. Problem is it has an intermittent miss at idle and will miss if if held at different rpm's. Car runs fine doesn't knock when logged but it idles rough and you can feel the car miss. Weird thing is I can turn the AC on or the rear window defroster and it basically makes the problem go away. Car has 30k miles on it and is rigorously maintained. It has been doing it for about 6-8k miles. Things I have checked/changed:
No boost leaks (no major ones atleast)
Put brand new OEM iridiums in
Changed different gas stations
Seafoam cleaner in the tank
Voltage seems good
Put in stock tune
I am leaning toward a bad injector, or wires, or maybe coils. Is there anybody else that has had this problem or might have an idea. I believe it has something to do electrically. I can turn headlights, rear defroster, or ac on and it goes away. Turn them off and it comes right back. I am stumped
Seeking professional evoM guru help.
No boost leaks (no major ones atleast)
Put brand new OEM iridiums in
Changed different gas stations
Seafoam cleaner in the tank
Voltage seems good
Put in stock tune
I am leaning toward a bad injector, or wires, or maybe coils. Is there anybody else that has had this problem or might have an idea. I believe it has something to do electrically. I can turn headlights, rear defroster, or ac on and it goes away. Turn them off and it comes right back. I am stumped
Seeking professional evoM guru help.
Last edited by dbsears; Apr 17, 2008 at 06:43 PM.
Apr 18, 2008, 01:41 PM
#3
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I can't really help much but my car is all stock and 3500 miles on it and i get a 5k rpm misfire at wot. i can also hear it miss at idle as well but i can't really feel it in the steering wheel
Apr 18, 2008, 02:20 PM
#4
Tighten the gap on your plugs if you have not already. .020
I assume it does this on the stock map as well as the custom map?
What are your fuel trims doing when you hold at those rpms to recreate the code?
I had similar symtoms that were finally diagnosed as a faulty injector. All 4 were replaced by Mitsubishi under warranty. No more P0300.
My car still has a small misfire at idle but I think it's normal or maybe due to a small exhaust / intake leak that causes my AFR's to fluctuate a little 14.6-15.2 at idle.
I assume it does this on the stock map as well as the custom map?
What are your fuel trims doing when you hold at those rpms to recreate the code?
I had similar symtoms that were finally diagnosed as a faulty injector. All 4 were replaced by Mitsubishi under warranty. No more P0300.
My car still has a small misfire at idle but I think it's normal or maybe due to a small exhaust / intake leak that causes my AFR's to fluctuate a little 14.6-15.2 at idle.
Last edited by Mr. Evo IX; Apr 18, 2008 at 02:25 PM.
Apr 18, 2008, 02:46 PM
#5
My plug gap is at .021-.022 right now which I believe should be fine. Yes it also does it on both my maps, actually had two different tunes thinking that was my problem. I am really leaning towards my injectors. My car did throw a P0304 once a while ago too.
Putting any type of electrical load on the car is what confuses me though. Could that affect the injectors? I will go log my fuel trims when I get home.
Putting any type of electrical load on the car is what confuses me though. Could that affect the injectors? I will go log my fuel trims when I get home.
Last edited by dbsears; Apr 18, 2008 at 02:50 PM.
Apr 18, 2008, 08:41 PM
#7
Have you noticed at all if you turn the AC on or rear defroster that the idle gets better? I am trying to figure out why putting electrical load on the car helps the idle. I need to get this figured out but in WA today we have had sunshine, rainstorms, hail storms, and now its snowing 
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Apr 18, 2008, 09:59 PM
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When you turn on an electrical "load" your engine must make more power to continue the same rpm. Log and watch the load number when you turn on these items, especially air. This can cause a load jump of 10. So with these items on you are running in a different part of your map than if you where idle without the extra load. You are also flowing more air to have this extra load which causes the airflow meter to read at a different rate. Possible answer, air flow meter reading low rate is not correct. Reading a little higher airflow rate now it is correct. Here are somethings to check:
I would really start looking at the items that contribute to idle control.
example:
Use an OBD II logger and monitor air flow at idle. You can then compare this number with spec for this car. This can point at an air leak in between your airflow sensor and turbo inlet. It could also point at a bad air flow sensor.
Look at o2 sensor output at idle. Does it switch back and forth from rich to lean?
Did you compare your wide band out put to your stock o2 sensor?
A bad or lazy o2 sensor can cause idle mixture problems as well as part trottle and cruise problems.
Have you run leaded gas in your car? This will kill o2 sensors. Sometimes within 5 minutes sometimes takes years. Very unpredictable.
How about your egr?
Is it leaking does it close completely?
Again can cause idle mixture problems
Last one is least likely as it would most likely affect high load idle as well.
Good Luck!
I would really start looking at the items that contribute to idle control.
example:
Use an OBD II logger and monitor air flow at idle. You can then compare this number with spec for this car. This can point at an air leak in between your airflow sensor and turbo inlet. It could also point at a bad air flow sensor.
Look at o2 sensor output at idle. Does it switch back and forth from rich to lean?
Did you compare your wide band out put to your stock o2 sensor?
A bad or lazy o2 sensor can cause idle mixture problems as well as part trottle and cruise problems.
Have you run leaded gas in your car? This will kill o2 sensors. Sometimes within 5 minutes sometimes takes years. Very unpredictable.
How about your egr?
Is it leaking does it close completely?
Again can cause idle mixture problems
Last one is least likely as it would most likely affect high load idle as well.
Good Luck!
Last edited by turboracer; Apr 18, 2008 at 10:03 PM.
Apr 18, 2008, 11:54 PM
#9
Evolving Member
The change in load cell when electrical load is happens causes an increase in timing which generally makes cars idle better.
If testing all the things in the previuos post, try upping the timing in your idle load cells. It should smooth things out nicely.
If testing all the things in the previuos post, try upping the timing in your idle load cells. It should smooth things out nicely.
Apr 19, 2008, 01:47 PM
#11
Alright I went and logged my car. You can see where I let it idle, then I turned on the ac and rear defroster. I then turned on the headlights. Once I turned all that off I held it at different RPM's. During this my P0304 code popped up again. If anybody can help me I would much appreciate it.
Edit: logs can be seen here: https://www.evolutionm.net/forums/sh...92#post5563492
Edit: logs can be seen here: https://www.evolutionm.net/forums/sh...92#post5563492
Last edited by dbsears; Apr 19, 2008 at 02:34 PM.
Apr 19, 2008, 08:09 PM
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P304 is cylinder #4 specific.
Switch injector from #3 cylinder to #4.
Then run car the same way. If code changes to 303 then bad injector if still 304 then continue to next step.
Switch spark plug from #3 to #4
If code changes to 303 then bad spark plug if not then continue to next step
Check compression on #3 and #4 cylinder.
What are the results?? Cylinder #3 much higher than #4 = bad news
About the same is good.
If good then possible coil shorting to ground?
Please report the results
Hope this helps
Switch injector from #3 cylinder to #4.
Then run car the same way. If code changes to 303 then bad injector if still 304 then continue to next step.
Switch spark plug from #3 to #4
If code changes to 303 then bad spark plug if not then continue to next step
Check compression on #3 and #4 cylinder.
What are the results?? Cylinder #3 much higher than #4 = bad news
About the same is good.
If good then possible coil shorting to ground?
Please report the results
Hope this helps
Apr 20, 2008, 02:34 PM
#13
Well I had a compession check last week. All the numbers were pretty good with #3 being a little lower than the rest. I am going to try to swap a friends coils/wires over to rule that out hopefully. Looks like my fuel trims are way off? Wonder what could cause that.
Apr 21, 2008, 09:28 AM
#14
You can just swap your coils with each other.. no need to involve a friend's coils. I'm still leaning towards an injector problem since your fuel trims are off. The fuel trim is a global fuel trim that's used in closed look to allow the car to run at 14.7 AFR for emissions / economy purposes. Since your trims are over 100 your ECU thinks your car is running lean and is trying to compensate.
Here's a hypothesis on your issue.
Lets say you have 3 properly operating injectors and 1 cyl with an injector that's not fueling. The ECU will look at the o2 sensor will notice that your overall mixture is lean.. and will start increasing your fuel trims to compensate. We don't know exactly what rules the ECU uses for P0300 but when I had this problem I found that the higher my trims got the more likely it would light a CEL. Like I could reset my ECU and drive a few days without a code and as my trims approached 120 in EvoScan I would get a CEL. Resetting ECU 0's the trims and it would start all over again until it got "out of bounds" and would throw a CEL.
There are other possible reasons for high fuel trims. Like an air leak in your charge piping post MAF, this will cause your engine to run lean at idle, then the ECU would compensate for the lean condition by raising fuel trims. This type of an issue will normally not be indicated by a P030x, since it would affect all cylinders.
Or an exhaust leak, o2 again detects lean because of air entering the exhaust during idle which makes the ECU "think" the cylinders are lean. ECU adjusts fuel trims upwards. Again this would affect all cylinders, not just #4.
Basically if the ECU thinks your lean if it increases trims, if it thinks your rich it decreases trims. 100 is the middle +- 5% is generally ok.
If you had a spark problem, that would likely result in a RICH mixture (unburned fuel) and the ECU would compensate by lowering your fuel trims. Not your issue.
Here's a hypothesis on your issue.
Lets say you have 3 properly operating injectors and 1 cyl with an injector that's not fueling. The ECU will look at the o2 sensor will notice that your overall mixture is lean.. and will start increasing your fuel trims to compensate. We don't know exactly what rules the ECU uses for P0300 but when I had this problem I found that the higher my trims got the more likely it would light a CEL. Like I could reset my ECU and drive a few days without a code and as my trims approached 120 in EvoScan I would get a CEL. Resetting ECU 0's the trims and it would start all over again until it got "out of bounds" and would throw a CEL.
There are other possible reasons for high fuel trims. Like an air leak in your charge piping post MAF, this will cause your engine to run lean at idle, then the ECU would compensate for the lean condition by raising fuel trims. This type of an issue will normally not be indicated by a P030x, since it would affect all cylinders.
Or an exhaust leak, o2 again detects lean because of air entering the exhaust during idle which makes the ECU "think" the cylinders are lean. ECU adjusts fuel trims upwards. Again this would affect all cylinders, not just #4.
Basically if the ECU thinks your lean if it increases trims, if it thinks your rich it decreases trims. 100 is the middle +- 5% is generally ok.
If you had a spark problem, that would likely result in a RICH mixture (unburned fuel) and the ECU would compensate by lowering your fuel trims. Not your issue.
Last edited by Mr. Evo IX; Apr 21, 2008 at 12:22 PM.
Apr 21, 2008, 10:36 AM
#15
Alright thank you very much. I believe I can rule out an exhaust leak because I have changed my exhaust almost 3 times. New gaskets and retightened everything. The only thing is I recently had taken off my exhaust manifold for the egt bung but it was missing before that so I am pretty sure thats not leaking. I am going to swap around my coil packs and put my leak tester on it today hopefully. Thank you for your help it is much appreciated 