All right. I've been looking over the last two days and have found nothing so I'm going to ask. The car already has a CAI, Borla TD exhaust, MD spacer, and Mrev2.

Monday and Tuesday I swapped my stock bits for Strupp headers and Titek test pipes. I spent the last half the day yesterday going over all my connections and hoses to make sure I didn't miss anything. I have everything together and I go hook the battery back up and go to crank the car and it starts and idles way high. I get out and find the inevitable vacuum line that i forgot to attach to the bottom of the CAI and the car just dies. I reattach the line and try and crank the car and get nothing. It spins and tries to start but no joy.

I try some more and no go, so for giggles I set it down off the jackstands the rest of the way to the ground ( I had a full tank of gas so I didn't see why it mattered) and it fired up for about 2 mins then quit. I gave up and came back this morning and it fired right up and ran fine until it warmed up then died again. I pulled the negative again and came back an hour later and it fired up and ran fine. After 15 mins I turned it off and now its back to the same thing, only this time I have a code P1615 NATS. I tow it to Nissan to have them make me some new keys and reprogram it, and it still doesn't stay running. Truck driver drove it right off the truck and parked it and then it started doing it again.

The tech at Nissan says its running too rich and stalling out, but with my aftermarket stuff he needs 2 hrs labor ($240) to check my work before he will diagnose it. It has not set a single code other than the NATS code.

Now all of my mods increase airflow and should make it run leaner, so I don't understand the tech saying it's running rich. I have never heard of headers and testpipes causing this particular problem on a Z and my NATS checks out now. I have no codes and when I tow the car back tomorrow, I'm checking the fuel pressure to see if the pump is failing intermittently.

Now my question is if anyone has any similar experience and any recommendations or other ideas? I have considered replacing the cam position sensors and crank sensor if the fuel pump checks out, just to be safe.

As of right now the car spins and does not crank, but every now and then fires and dies immediately. On very rare occasion it starts and runs for a minute or two. No smoke or gas smell, no noises, no codes, everything appears hooked up and working. I have unhooked the negative twice to reset the ECU.

 

Headers and test pipes have little to do with the motor running poorly. You can run the car without either.

The exception is the pre and post-catalytic converter oxygen sensors. These are important sensors. Are all 4 OK?

 

That was my understanding (evidently not Nissan's). What I changed should not have effected anything on the car.

As far as I know the O2 sensors are perfect. I pulled the cats and manifolds with them installed (I didn't bump or hit them on anything) and swapped them one at a time to their corresponding new locations as I put the new parts in. I didn't get anything on the portion of the sensor that sits in the exhaust stream.

I get no codes for them being out of range either, although I plan to log their voltages and check them when I pick the car up tomorrow.

I also will run the fuel pressure and pump input voltage while I attempt to start the car and make sure the relay and pump are functioning 100%.

Unfortunately I couldn't get the car back from them today after they supposedly fixed the NATS code.

 

How did the Nissan tech. determine ur car is running rich? By monitoring the o2 sensor activity thu their factory scan tool?

I am just try to give it a guess, but I may be wrong. Did you check out the exhaust manifold gaskets, any leak there? And how about the headers flanges (which connect to the engine), are they sit flush to the cylinder heads? I have seen some header flanges are wavy and causing exhaust leak. Did you over torque any bolts, it may damage ur cylinder head/ header?

Usually when the car is cold, computer will ignore o2 sensor readings unit they reach certain temperature, so if anything leaks before the o2, the computer will not catch it nor trying to adjust when it is cold. As you said, once your car warms up, it stalls. That got me think something is messing up the o2 reading.

Plus, if there is a exhaust leak at the header, o2 sensor will provide a false lean reading to the ECU, then the ECU will increase fuel to the engine for compensation. So your car is actually running rich! And with all the excessive fuel, your engine will not run properly.
Check your spark plugs and see if they are wet.

 

The tech didn't put a scanner or consult on it, he just told me what I already knew, it only cranks every once in a while and when it does it revs to 2500 and then the ignition cuts out. He said "It run rich. It run like crap." in a heavy Asian accent then told me it'd be a minimum of $240 to look at it. When I asked him if he had any ideas why it was running rich, his answer was "You screw wit car, this wat happen." So I towed it back to my house.

It doesn't miss or act funny when it's running, and it it will start when its warm, its just harder. I have gone over my exhaust connections and I can't find anything leaking yet, but the car doesn't crank often enough for me to conclusively tell if its leaking. I am going to attempt to check the O2 reading next time I get it cranked, but it runs normally when it runs, when it doesn't you can smell the gas in the exhaust as its cranking. Also it doesn't stall out as much as it just shuts off. Like I turned off the key while accelerating.

 

I would never ever ever ever go back to that dealer/mechanic again. If he doesnt understand performance mods and thinks your "messing with the car" then he has no right to touch your vehicle.


I would start with square 1 when you started whatever you did with the header install and figure out what you screwed up. If it worked fine before then obviously you broke something along the way.

 

Ok guys. I found the problem.

When I moved the harness to get to the passenger precat O2 plug I undid the wiring loom ground in the very front of the motor. I forgot to attach it when I went back up causing a faulty crank position sensor signal.

Fun part... I bought 2 new crank sensors from Autozone and one from Oreillys and all 3 set the P0335 code for crank position. The original sensor never set a code . So I run the diagnostic tree on the code and trace the grounds they recommended and viola, found the problem. The occasional contact made for the occasional firing. Interestingly the new sensors took several more revolutions to crank and still set the code so I put the old one back in and now it cranks instantly and runs fine. I'll be getting a new one from Nissan, although the Autozone sensors matched the factory one down to manufacturer's stamp and part number. Not sure if there's a difference, but here's hoping.

In summary, my crank sensor was not correctly grounded but it did NOT set the corresponding trouble code. The new sensors set them regardless of the problem being remedied. Hope it helps if it happens to someone else.

 

Glad you figured it out!! Good Job!

 

Thanks. I knew I did it (or rather didn't redo it) when I swapped parts over, but I could not find the issue (engine cover was on and hiding it). I rechecked everywhere I remembered working and found nothing, and with no code at all, I had moved to fuel pump/ignition relays or anything else I could think of that could possibly be outside the ECU diagnostic program.

The fact that it didn't have enough sensor resolution to ignite, but had enough to keep from setting the code baffles me. The coils were firing normally as well according to the Fluke data logger I hooked up to them.

Of course when I stared at the motor, cover removed to log the coil voltage earlier and saw the ground flopping, I just about screamed "Son of a b*tch!" After 6 days of scratching my head....