Misfiring at idle
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Joined: Oct 2015
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Misfiring at idle
Hello all,
I will try to keep this as short as possible:
I have had my stock 2009 G37x sedan since 2014 and did not experience any mechanical issue up until a couple of months ago. A week or so after having installed a stillen gen3 CAI @ 160k miles, the car threw a P0300 CEL. Three mechanics and a visit to the dealership later and I am still unable to fix this issue!
What was replaced:
Spark plugs
Ignition Coils
Fuel Injectors
Manifold gasket
Factory ECM - Yes! $$
What was tested:
Compression - Both at idle and running
Vacuum leaks - None
Test pipes - No issues
This is what I can remember. I don’t understand how this issue is not able to be properly diagnosed and fixed accordingly. I have spent roughly $3k so far and do not plan on spending that much more. I received a call from the Infiniti dealership telling me that they now believe that there is a “small combustion leak from the valve”. They also said “burnt cylinder/valve”. After the estimate they gave me to repair that, I promptly told the service manager to take a ****ing hike and picked up my car the next day. I would really appreciate any insight from the community as I would like to get this fixed once and for all. Please let me know what I should do. As much as I’ve considered it, getting rid of the car at this point is not an option. Thank you for any input!!!
I will try to keep this as short as possible:
I have had my stock 2009 G37x sedan since 2014 and did not experience any mechanical issue up until a couple of months ago. A week or so after having installed a stillen gen3 CAI @ 160k miles, the car threw a P0300 CEL. Three mechanics and a visit to the dealership later and I am still unable to fix this issue!
What was replaced:
Spark plugs
Ignition Coils
Fuel Injectors
Manifold gasket
Factory ECM - Yes! $$
What was tested:
Compression - Both at idle and running
Vacuum leaks - None
Test pipes - No issues
This is what I can remember. I don’t understand how this issue is not able to be properly diagnosed and fixed accordingly. I have spent roughly $3k so far and do not plan on spending that much more. I received a call from the Infiniti dealership telling me that they now believe that there is a “small combustion leak from the valve”. They also said “burnt cylinder/valve”. After the estimate they gave me to repair that, I promptly told the service manager to take a ****ing hike and picked up my car the next day. I would really appreciate any insight from the community as I would like to get this fixed once and for all. Please let me know what I should do. As much as I’ve considered it, getting rid of the car at this point is not an option. Thank you for any input!!!
Thread Starter
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Joined: Oct 2015
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Seems to be the only thing that's really been altered that could be the root of your issues. Is there a chance you switched the driver's side and passenger's side MAF sensors around during the install? Doesn't really make sense but I've heard horror stories when they're mixed up it causes all kinds of issues but the problem is corrected when they are switched back. Maybe start there since it's a 5 minute trouble shoot.
On my car, I get the P0300 code every so often on cold starts. I don't notice any hesitation or sounds like an actual misfire. I do get the higher idle but that's due the code. As soon as I clear the code with my scanner, the idle drops to normal. I haven't had the code in about 3 months. But it just comes and goes for me.
I also changed sparked plugs, cleaned the MAF and cleaned the throttle bodies. If you're car isn't truly affected by it, I'd say just go to Autozone, have them clear it and continue on. I bought a cheap scan tool off ebay just for this.
Latez
I also changed sparked plugs, cleaned the MAF and cleaned the throttle bodies. If you're car isn't truly affected by it, I'd say just go to Autozone, have them clear it and continue on. I bought a cheap scan tool off ebay just for this.
Latez
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Joined: Apr 2015
Posts: 1,153
Likes: 183
From: ATX
If this random multiple misfire code started happening a week after you installed the aftermarket intakes why did it never cross your mind to at least try re-installing the factory air boxes to rule it out? That's the easiest and cost effective first step you should have taken. Rather than throwing $3,000 at the car because of a $500 set of aftermarket intakes..
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Thread Starter
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Thank you all for the responses. I asked the mechanic to put the stock air boxes back on but I’m not so sure that he did. I will swap the MAF sensors first to see if that changes anything. If not, I’ll install the stock intakes. I have decided to take a practical look at the situation and decided not to be upset about the money that was spent. I consider it maintenance completed for the next few years. It helps me sleep at night. Will keep the thread posted.
Thread Starter
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Difficult to imagine he did this... PITA to swap a long-tube intake off then on again.
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This particular mechanic had the car for 2 weeks... In fact, so did Infiniti and the others. They all assured me that the intake wasn’t the cause of the misfire. We will soon see.
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has the car sat for extended period of time?
if the intake swap to stock didnt help i would start with the basic. At this point you need to try anything you can. Assuming the stock intakes are back on i would do a spark test make sure spark plugs are clean and no injectors are leaky, coils are good etc, also check fuel pressure for fuel pump, see if injectors all click, gas is good.
Ive had an issue like this it ended up being the fuel pump but the dealer picked it up on they're scanner.
The one sensor it could be is the maf or map since it picks up manifold pressure and tells the computer what mixture to send out.
if the intake swap to stock didnt help i would start with the basic. At this point you need to try anything you can. Assuming the stock intakes are back on i would do a spark test make sure spark plugs are clean and no injectors are leaky, coils are good etc, also check fuel pressure for fuel pump, see if injectors all click, gas is good.
Ive had an issue like this it ended up being the fuel pump but the dealer picked it up on they're scanner.
The one sensor it could be is the maf or map since it picks up manifold pressure and tells the computer what mixture to send out.