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Hello!
I recently bought a 2012 g37x. I love to be thorough with a "new" car and will be changing all the fluids etc.
I seafoamed the engine the other night via the brake booster line. I have done this to countless other vehicles. Sometimes I notice a difference and sometimes I do not.
After seafoaming and running it a few miles. I noticed the engine has a "stumble" in the idle. Idle is at normal rpm's and about every ten seconds or so it stumbles. I say stumble cause it doesn't feel like a misfire. It does this in neutral or drive. Driving car slowly or underload....everything seems normal.
I think I may have fouled a spark plug while seafoaming. I have ordered the factory iridium densos (3457) but they wont be here until next Friday(10-14).
Wanted to see i anyone else has run across this or has suggestions.
I reset the ECU twice since the stumble appeared and it doesn't seem to effect it. The stumble is still preset. I have cleaned throttle bodies and the MAF were spotless.
Thank you for your help and suggestions in advance. I will of course report my findings after I change the spark plugs.
My 2009 has 74K miles and developed the idle stumble. I thoroughly cleaned the throttle bodies. The job took about an hour. REMINDER: DON"T REMOVE THE TB CONNECTOR. The engine runs great now, no stumble.
BTW: cleaned with Carb/Choke cleaner sprayed onto a rag. Also spray cleaned the MAF sensors with MAF cleaner while I was at it.
Do you have a check engine light or any engine codes? Did you double check the brake booster line and any other vacuum lines you disconnected? This can also cause a rough or stumble at idle.
Yes, there was a CEL after seafoaming. I cleared it doing the ecu reset. It hasn't come back yet. I will double check the vacuum line when I get home tonight. My wife is currently driving the car.
I did notice that you cleaned the TB's. Mine were fairly dirty. I also noticed a slight stumble today but not like it was previously. I also put Heat into the gas tank. I don't think the problem is completely resolved. I did not have any CEL. The other thing I do notice about my engine is that it starts fairly hard. I takes several seconds and maybe four or five compression strokes to fire up. That reminds me of a problem I had with a bad fuel pressure regulator diaphragm that allowed the fuel pressure to bleed down and also dripped raw fuel into the intake at idle. I will keep an eye on the gas mileage.
While driving around last night with my friend who is a mechanic the engine finally threw a code. P305...bad ignition coil. I will be replacing the spark plugs and ignition coil today. Im pretty confident that will clear up the stumble. I'll confirm what happened when I finish.
Car is stumbling worse than ever again. I have noticed that when the temperature (OAT) rises, the car stumbles more. When the OAT dropped to around 40degF the car did less stumbling. When the temperature rose to around 70degF the car started fumbling and bumbling. Still no CEL. I expect the ECU to somehow pick up on something. Maybe a low fuel pressure, misfire, etc. I am going to start to look into the fuel pressure regulator. I will also look into the plug/wire/COP possibility. I sure would like a CEL to show that misfire as well.
Update: Car still stumbles at around 50degF
I will hook up the scanner and check for pending codes. I will also check the fuel trim both long and short term to see if there is excess fuel that the ecu is trying to trim out.
Last edited by Skatetrainer; 10-19-2016 at 05:12 PM.
Jsolo and Epiphany....Thank you for your interest. I haven't been checking the thread because the coil comes in tomorrow. I will be replacing the plugs and the coil tomorrow....
I do not know if the coil is causing the stumble for sure but they were only $50 and its location near the firewall made me think heat might have contributed to the failure. Again, I am guessing.
I try to be a technician...not a "parts swapper". I didn't want to deal with the stumble for another week if it was a coil.
My friend(mechanic) checked the codes with an OBDII scanner. What bothers me is that it only stumbles at 650/1000 rpms. Initially, it wasn't throwing a code but after driving it for a few minutes it threw the CEL light and we saw P305. My mechanic/friend didn't say replace the coil...he recommended swapping coils to see if the coil was the actual issue. I thought I would roll the dice for $50 and grab a coil.
Now, there isn't a CEL. But the idle still stumbles, the behavior is consistent. In my experience coils typically work or don't work at all. So, this situation is very frustrating for me. Trying not to think about it too much until tomorrow.
Thank you for your interest in this thread. I will post my findings tomorrow evening.
I'd expect a coil to show signs of failure at higher than idle rpm. That's when they're subject to more [electrical] load. Swapping coils around is a good idea to see if the misfire moves to another cylinder. I would of done that before replacement.
I changed the spark plugs and coil yesterday. Reset the ECU by disconnecting battery cable for an hour. I have reset the ECU using the other method mentioned in this forum but something about disconnecting the battery gives me the warm and fuzzys.
Car is idling at 650/700 very smooth no stumbles!
The throttle at low speed, especially from a stop, feels much more responsive. Its still a little delayed compared to my Acura(which was a traditional throttle cable). No surprises there.
All the spark plugs that I removed looked pretty good for 75K. They were a consistent color and nothing looked damaged or worn out.
No pending codes. Car continues to stumble badly. Very intermittent - no perceptible pattern - frustrating.
Update: 11/19 - Cold weather and a storm in Mpls. revealed a bad battery - wouldn't start. The car has always started very slowly, several revolutions needed even when warm. The voltage drooped to 9.6V during start and 13.8V after start. The battery is only 9mos old. It was replaced at the Nissan dealer. Group 35 - 550 CCA. New battery replaced on my own cranks the starter fast. The car starts instantly.
Could that have been the problem? A junk Nissan battery? I will post an update....
Wouldn't hurt to have the battery load tested. What's your driving patterns like? Could be too many short trips not letting the battery get recharged properly. Bad batteries can cause all kinds of weird problems in cars when the voltage isn't just right.
10-06-2016, 03:05 PM
