Car is not running right. Rough idle and misfiring under acceleration.
 

I have updated this post because I still have not been able to get the car right. I have tried numerous things and nothing has changed. If you have any suggestions please feel free.. Thank you.


What I have tested/eliminated:
Cats
Fuel pump
Injectors
Coil packs
Spark plugs are good
Air filters replaced
MAF and TB cleaned
PCV valves cleaned.
Checked for vacuum leaks
Replaced valve cover and spark plug gaskets( though for sure that would fix it as there was oil alll over spark plugs )

As i stated before I checked the spark plugs, they look fine and they have about 55k miles on them.

I’m making this post in hopes anyone has any other tips ideas. I’m kinda at my last ditch effort here. Gunna get my boost leak tester from 300zx to be 100% sure there’s no air leaks.



Hello everyone, I have a 09 370z (mods in signature) and am having a issue with idle and WOT acceleration. No check engine light and no pending codes besides random misfire. Once car is warmed up it sounds like the engine is misfiring at idle, i can feel it shake the car very slightly every time it happens and it’s pretty consistent. Under WOT the car will be pulling smooth up until about 4-5k then it starts to break apart. If i keep on the gas it will break apart then pull smoothly again and it continues to this back and forth. I’ve check my air filters, cleaned the MAF, and MAP sensor. Fuel pump was replaced 35k miles ago and spark plugs changed out about 45k miles ago. Was going to check fuel filter but all it is is a black mesh piece attached to the fuel pump assembly. If anyone has any idea please post them.

Possibly dirty TBs. Could also be a sensor going out.

Since cleaning TBs isn't all that easy (not all that hard, either, but I'm lazy), first I would try is resetting the ECM - pull a battery terminal and step on brake pedal for 2-3 seconds or there is a video-game-worthy procedure (search is your friend).

Okay thanks Im going to clean the throttle bodies today hopefully that will help. Still haven’t got any check engine light or pending codes.

Sounds like you have vacuum leak. Wouldn’t be surprised if you had a loose clamp on one of the throttle bodies

I had this almost same problem with one of my last Z’s. The culprit could be faulty ignition coils and/or a possible vacuum leak. I would test your ignition coils and check for any vacuum leaks. Also replacing spark plugs in your Z by time or current mileage is a better rule of thumb never wait 100K miles to change your spark plugs as Nissan would recommend. If you have to change your coils you mite as well replace your spark plugs since you will be in there anyway. Best of luck with your diagnosis.

Update: cleaned the throttle bodies they were disgusting I was hoping that it would be the problem but no luck it’s still doing the same thing. Going to test the ignition coils tomorrow. I searched high and low for a vacuum leaks but was unable to find anything.

If anyone else has some ideas let me know please. I doubt it’s the fuel pump but I’m going to check that tomorrow too.

Make sure your ground at battery is solid and clean where it connects to battery and body of the car, when my ground wire became loose it would seem like it was misfring and AFR was very rich, then next day it would be fine then it would start over once warmed up.

Just a heads up, mine had something similar and it was a damaged injector and it ended up frying the computer.

Okay I’ve checked a lot of things since last posting. Not fuel pump as i checked it with a gauge, it could be a injector I’ll double check that next. Negative cable is good, spark plugs were not bad either.

I’m really starting to think it’s my cats. They are Z1 Motorsport cats and I’ve had them for about 40k miles. The problem is so inconsistent it’s hard to diagnose. Today i hopped in and fully accelerated and i had like maybe half the power and the engine sounded really muffled almost like i had an exhaust leak but it was quiet( if that makes sense). Stopped the car went to class then came out an hour later, full throttled the car with no problems at all.

I’ll try to take a video next time it happens and upload it. Thanks for everyone’s input so far.

Clogged up high flow catalytic converters is another possibility to your symptoms your are experiencing with your Z. How knows what vendor Z1 is using to supply their high flow catalytic converters and how good of quality they are?

I’m going to lift the car up this weekend and check to see if that’s the problem. I guess I’ll have someone rev the car at about 2200 rpm and test the airflow coming out of the exhaust pipe (right off of the cats).

Anyone have any other ideas as to how to test a clogged cat?

Google is your friend.

https://www.google.com/search?q=how+...hrome&ie=UTF-8

Thanks everyone I’ll check into that this weekend. I’m leaning toward it being the cats simply because of how bad my car is running and it will not throw a check engine light. If i have half the power and my car is running like crap it should throw a code. My cat codes have been permanently disabled through uprev.

Sadly it is not the cats i checked them today. I’ll keep looking for the problem it’ll turn up eventually lol. Thanks for the reply’s

Update
 

So here we are, the 370z still is running like ****. I took a break and focused on the 300zx but now I need to get back to it.

What I have tested:
Fuel pump
Injectors
Coil packs
Spark plugs are good
Air filters replaced
MAF and TB cleaned
PCV valves cleaned.
Checked for vacuum leaks
Replaced valve cover and spark plug gaskets( though for sure that would fix it as there was oil alll over spark plugs )

As i stated before I checked the spark plugs, they look fine and they have about 55k miles on them.

I’m making this post in hopes anyone has any other tips ideas. I’m kinda at my last ditch effort here. Gunna get my boost leak tester from 300zx to be 100% sure there’s no air leaks.