The same thing happend to me, my car was shaking and all the other stuff you guys described. So I had my car towed to the dealership, and it took them about 5 days. They didn't know what was wrong with it, then finally they told me piston #6 was misfired they fixed it and my car running fine. O yea when this happened my car had 13,000 miles on a 2003.5, Hope this helps

 

Too make sure that its a missfire have your car hooked up to a smog machine and if your HC's (Hydrocarbons) read high then you most likely have a misfire.

 

Which is why its great to use a 5 gas machine! Its basically a smog but without the dyno. The only thing that you need the dyno for is to test for NOX so its actually a 5 gas machine, but your only reading 4 gasses.

The only way to see the HC's really jump is if its a constant missifre, like a completly dead cylinder. If its just a quick bump in the idle condition your not going to see more than 3-4 PPM change in the HC readings. With the gas analyzer though you can see exactly which is bad, high CO would be un burned fuel so your looking at an ignition problem or a stuck open injector. HIgh 02 would be too much oxygen so youd trace down a stuck closed injector. I could go on but it would be a waste of my breath. Too many people think that just because they know how to pull codes from a scan tool that they are the best tech out there. Im young, but I learned from 2 old guys and 3 young guys so I have the knowledge of the new and old diagnostic methods. The sad part is that a lot of dealership "techs" are this way, they can bust out services and pull codes, but cant truly fix anything.

 

Yo G35mechanic is the 5gas machine your talking about the same as a oscillascope, where you can test 4 gas's (HC,NOx,o2,c02) and the 3 different ignition patterns (raster,superimposed and raster)?

 

I am having the same problem, only when idling at a traffic light or stopped, kinda like a thump. I think it's normal, my car has been doing it since i bought it.

 

I had this problem as well...it wasn't a thump tho..more like the engine knocking. I was filling up with Citgo gas before, but now i fill up with Shell's premium and i beleive it fixed the problem. Try switching gas brands, it may fix it.

 

The three ignition patterns are Display (AKA: parade), raster, and stacked (what you call superimposed). You will need an ignition scope to read the ignition patterns, most ignition scopes have a built in o-scope and voltmeter. An oscilliscope is a way to graph voltage, think of a heart meeter when your in the hospital but ony its for electricity. Think of an O-scope as a very sophisticated voltmeter.

Most tune up shops should have a gas analyzer. The 4 gasses are HC (hydrocarbons), CO (carbon monoxide), CO2 (carbon dioxide), and 02 (oxygen). The 5th gas is NOx which can only be present when the engine is under a load.

 

Well, they checked each injector, the mass air flow sensor and a couple of other things. They still haven't pinpointed exactly what it is, but they are going to try replacing all 6 ignition coils. We'll see how that goes... should get it back tomorrow.

 

It seems as though it was one of the ignition coils. They replaced all of them due to the fact they couldn't pinpoint the cause. Since then, it hasn't happened.

 

cripes, not coils... man, that was such a hassle on my 5th gen max. I hope I'm not going to be messing with that on my G too. I also have alot of loaping at idle. :/

 

I have the same problem and my car only has 3k miles. It only happens at idle and after the car has warmed up a bit. I told the dealer and it didnt make the sound at the dealer. Next time I go to them I am going to leave the car on and let them come hear it. It also rarely happens when I open the hood. Its the weirdest thing. I am also lost on this situation..I would reallly appreciate it if you find out what the problem is please email me at hmocreia@aol.com