Background on car.

2004 350z 5at
Built Long Block
Twin GT30r's
Osiris/Utec EMU


I was driving the other day doing around 45mph when my car suddenly starts to stuttered and just shut off. I managed to get it pulled on to a small side street. I then tried to crank the car again. Car turned over but sounded as if it was only firing on 3 cylinders.. it had a distinct miss to it but not mechanical sounding issues of any sort. ( bearing noise or rod noise ). It is at my shop right now I have not had a chance to diagnose the problem. Here is a list of what I think it maybe....

No codes were thrown. I hooked my cipher cable to it and no codes were listed...


1. Im thinking it may be the crank sensor ?

2. My utec took a crap on me. ( I have osiris on the bottom with a base tune so I can check the utec by unplugging it and letting ecu run the car alone )

3. Timing chain Tension broke ?


I will be working on it either tomorrow or through out the week end, so if any one has any advice I am all ears. I will also keep updates on here of what I find while looking.

Thanks in advance to any of you that help.

 

Check your coil packs for the tell-tail melted bubble near the connector. UTEC has a tendency to blow coil packs.

 

I have changed out all coil packs with ones from another z that runs. Still has miss fire.

 

but it runs now?

does your CEL blink? no codes is not good. your reflash doesnt have them shut off does it? a bad crank sensor would pop a code.

i assume you aready pulled and examined all your spark plugs? no crap in the radiator fluid?

 

+1 I didn't see he had no codes... when I lost a single pack I got two misfire codes almost instantly. I keep saying this I sound like a broken record... check all your engine grounds make sure they are tight especially the two at the front on the timing cover. Make sure UTEC is grounded (black wire to ground). Lastly, make sure no water is leaking through the main boot onto either EMU.

 

Car will crank but idles rough and wants to shut off if no throttle is given. My osiris rom does not have the codes turned off. Nothing on dash as if the car is running fine.

I have only been able to check 3 plugs so far. All on the driver side. I will tackle the passenger side if needed tomorrow. Plugs look find. The top of the pistons look ok as well. No signs of steamed piston from lifted head gasket. Have not checked the actual rad fluid yet, but that is something else to add to the list tomorrow if my first ideas fail.




Checked all grounds first thing along with fuses just for peace of mind. I am going to check the ecu and emu tomorrow to make sure all grounds are still secure. I am seriously leaning towards utec going bad. I have diagnosed a utec going bad in the past on a different car. This is acting the same way. Fortunately i have a base rom on the osiris so the car will start and run if utec is not connected.







Thanks for all the help so far. I will let every one know as I continue. Hoping for easy solution but when it comes to this car there are never easy solutions....

 

your MAF sensor is plugged in properly and clean?

 

Was it raining when the problem started? I favor UTEC also...

 

Update...... had some spare time today. Took the utec out and plugged in ecu alone. Problem still there. Car will crank for 15 secs or so before shutting off. Car sounds like its only running on 3 cylinders.

Tomorrow I will replace crank sensor with a spare I have.

 

Ok so today I put the car on the lift and found this ....








Needless to say i cut the plug off and re connected it to another plug I had from a spare harness along with a new crank sensor. After that I then tried to crank the car. Now the car will not crank at all. It back fires really bad on start up.

No I feel that the plug fried my ECU ? Any one else think this ?


New question is I have a spare 04.5 manual transmission with osiris on it for my 6mt conversion I was going to do. Can I plug that ecu and try to start the car ? or will the fact its a 6mt ecu make it not work ?


Any advice would be good right about now.

 

doesnt make sense. you should have got a crank trigger code. and aside from that, the car will run decent with no crank trigger, it will take longer to start while it looks for the signal and then default to run off cam triggers alone and give a check engine light. i could see that perhaps with the UTEC it might not do that as the UTEC is most likely intercepting the crank trigger signal and manipulating it, and the UTEC might not be able to run without it... but on stock ECU only i dont get it.

 

Update. I will be switching out ecu today at some point. Hope that fixes the problem. From what I have read seems to be a good bet.

 

Are you hearing any other abnormal noises form the engine as well? ticking, slapping, anything of the sort? You'll get the backfire if the cylinders aren't firing properly and fuel is being dumped into the exhaust.

 

This is correct. There are no abnormal noises at all.


About to change out the ECU now. Is there anything that I might be able to cipher ? to see whats going on...

 

compression test?

 

Waiting for jared from uprev to email me the Rom file so i can load my Rom on the new ecu i got.... So still no real results.

 

Good chance something fried in your ECU since it looks like all three wires on that harness got shorted to ground.

 

That's what i am thinking but when i called uprev and spoke with Roger? he said it was unlikely that the sensor fried the ecu. Which i think is bs due.

 

it needs more WIN.

 

That was a lotta help^^^