I have an 04.5 touring 6spd with about 22k miles on it. Nismo CAI and exhaust, everything else mechanical is OE (aside from brake pads, filters, fluids etc.). It has Mobile 1 oil and filter, but I doubt that makes any difference. The engine oil is only about 2k miles old, and I check it regularly, still looks and smells fine, and is at the proper level.

At idle when it's up to normal operating temperature, the engine seems to have an individual miss that happens once approx. every 15 seconds, sometimes longer in between misses. I can see the RPM drop a small bit, feel a slight shudder and hear an individual clunk noise, all happening at the same moment. On cold start ups, where the car is on high idle I haven't noticed it happen. Off of idle, it runs great.. there are never any hiccups in power delivery, or any unusual sounds or anything that you would notice as out of the ordinary.

At first I thought it may have been bad fuel, but I have run about 4 tanks of fuel through since I noticed the issue and it still continues to happen. At that point it was the end of the driving season, and I put the car into storage. I haven't driven it since, just been using the winter car. I always use premium fuel, which around here is 93 or 92 octane depending on the station. Shell most often, or if I am out of my area, I have used probably all other brands but always go to the high volume stations where the fuel is less likely to be old.

I figured I'd bring the Z into the Nissan speed shop in the spring and have them check it out. Has anyone had this issue before? Does anyone have a suggestion of what it may be?

Thanks.

 

Could Be as simple as a spark plug, Or mabey a coil. I have seen bad coil clips be the cause of misfires.
You are more than welcome to bring it by. we would be glad to look at it for you.

Thanks,
Tim

 

Thanks for the reply Tim. SP and GRD were the speed shops I had in mind. You both have good reps, and neither are too far away from me. I figured that one of you would be willing to fix it.

I have my insurance on suspension mode now since it's not being driven in the winter. I was planning on bringing it in for service when spring arrives and I start driving it again.

Thanks again.

 

Hey mike, have you found out what was causing it? would appreciate some input, as I have the same problem, started just yesterday. I have a 6mt g35. Happens only on idle, car shudders and rpm drops slightly, clunks only when gear is disengaged (seems like the shaking engine causes a harmless clunk in the gearbox?), anyway, it drives fine.
I did some search here and many seem to agree its the throw out bearing, wanted to change my clutch for a while so I think now is time.
Thanks.

 

is it a clunk or a rattle. the throwout bearings in our cars always make noise from the factory. all 3 of my z's have a little back fire to them even with stock cats and exhaust. idle never stays even. im pretty sure its normal.

 

Turns out that clunk in my car (same symptoms reported by those with bad bearing) only came when I was driving without my brake master cylinder (took it out to replace it), anyhow I've installed a new one and symptoms are gone, so perhaps those with same symptoms should check and make sure their brake master cylinder is tightly bolted onto the brake booster.

 

I took my car in to SP earlier this year and they couldn't find the problem. They suggested that I take it to the dealer and have them scan the car with the better diagnostic computer that each dealership should have. I never took it to a dealer. It still has the shudder, which from what I hear, a lot of z33's have. I am not too concerned about it, since SP saw nothing obviously wrong, other people have the same issue, and the car still runs good.