current issues. while driving down the highway heard a noise comparable to a snapping and experienced a loss of power. while going to a safe place to park. after the first initial turn off the car did not start again and had to be towed, while otw to the “safe place” my RPMS fluctuated to a point higher than normal in each gear from third down to first gear. would not go out of first. took a code reader to it and pulled misfire in cylinder one and another one for improper fuel air ratio. installed a new spark and coil pack for cylinder one just to see if it would fix the problem and now the car refuses to start. it’ll try but just struggle and won’t turn over. any ideas

 

snapping noise and loss of power doesnt sound good. Were you still able to drive it home like that or once you parked initially after it happened it never started back up? I would do a leak down/compression test before anything. Also sounds like the transmission may have gone out.

 

No the car did not start again after i turned it off the first time, it had to be towed. once it got home and we did an oil change it would start but it took a few tries and it still barely started

 

Have you done any other work recently to the vehicle? Misfire symptoms don't usually pop up out of nowhere. How many miles on the Z? What year? Have you already serviced/replaced the Cam and Crank sensors? Have you been running the engine hard? Can you confirm the starter turns the engine over, perhaps I misunderstood your wording, but the crank is rotating with the starter, it's just not firing?

Based on what you described, this sounds like a timing issue (stretched timing chain, or chain jumped some teeth, or broken guide/tensioner) or at the least the ignition system is unable to determine the proper timing (bad sensors).

As bre240z mentioned, doing a compression test and/or leak down test would help determine if your engine has a more serious underlying problem. I would start there, better to find out if you have a catastrophic internal failure before throwing parts at it. Fingers crossed you didn't have valves contacting cylinders or pinging, there's some hope since only one cylinder is complaining about misfires.

Without more detail it's difficult to diagnose, I could be completely wrong and this might simply be a bad fuel injector or fuel pump issue. Many things could display symptoms you are witnessing. As for the RPMs running higher while in gear, that could be related to a broken trans or more likely, a bad clutch. The snapping sound could have been your clutch failing, but that doesn't exactly explain the misfire condition or crank - no start.
Cheers!
-Icer

 

it’s an automatic 2003 Nissan 350z Enthusiast. The only current modification is a K&N intake, it is my daily and does get driven decently hard about 20-30 mins per day to and from work. it’s got 175,000 miles. no service on any cam or crank sensors- the starter does turn the engine over it just won’t fire. (this was after we put a new plug and coil into cylinder 1) before hand it took a second but it would crank and turn over and just barely fire but it still started.. i ran it around the block a few times. it ran okay at first but as soon as i went to go up my hill it started to misfire and backfire pretty loud on a stock exhaust and just over would not run good. ever since the new plug and coil that was installed last night it still cranks and turns over but no firing at all

 

Make sure you use OEM coils and I would recommend the OEM spec NGK plugs. These cars are picky about their ignition electronics. Based on your description, I believe you're due for the cam and crank sensors. My brother had an 03 G35 with AT & similar mileage. His G had very similar symptoms, replacing the sensors resolved his issues. But, even after getting it running right again, it was clear from leak down and compression tests that the engine needed to be overhauled or replaced (that's what extended oil change intervals does to these engines).

There's still the potential for timing chain stretch (wear) or some kind of tensioner or guide issues, but if it's cranking over, it doesn't sound like you have piston to valve contact. Still, I would do a compression test at a minimum to rule it out before proceeding with replacing the cam and crank sensors. Use OEM parts, cannot stress that enough.
Good Luck!
-Icer

 

Would it be possible that i have blown a head gasket?

 

Anything is possible.

Do you have white smoke coming out of the exhaust? Is the oil milky?

If not, the HG is probably not blown.

 

no i do not and okay. i just swapped the fuel pump relays and replaced the cam position sensors and still nothing. in a moment i will be doing the crankshaft if i can’t find anything else that’s small that could be apart of the problem. it turns over and is trying to fire really bad but won’t. any ideas? maybe a timing chain? i’m not for sure but this very well could just be a ton of tiny issues making one big issue

 

Check your fuel pressure. Might have a bad fuel pump or low fuel pressure. A simple test would be to spray some starting fluid in the intake and see if the car is able to start and run for a few seconds. If it does, you just found your problem (fuel delivery).
Cheers!
-Icer