alright so recently i put in my new motor with all the goodies(headers,rod bolts,etc). i also installed a 350z flywheel,and clutch setup. everything was going great and the car ran awsome, i installed a SAFC and got an LC-1 (not yet installed). the problem im having is a power loss. its not consistent, it sometimes will happen randomly. at first i thought it was bad gas, not the case. so i checked my SAFC wiring,everything was good. swapped MAFs with a good one, no change. when installing the Z flywheel we had to notch the bell housing for the cps, so i checked the sensor,nothing wrong. recently i noticed if i dont give it enough gas when coming from a stop(start to bog alittle) the problem will start. no check engine lights or anything. and the wierd thing is, if its running like crap and i shut the ignition off while driving,let it sit for acouple seconds and then start it back up,it runs great again. anybody ever had a problem like this? any info would be great

 

I hate intermittent problems. Always a ***** to diagnose. I'd say it's a wiring problem, maybe a short somewhere...

 

You sure the cranksensor is reading the flywheel properly?

 

before we relocated it, it would throw a crank sensor code, we moved it over and its right in the middle of the ring.but i think that would be a constant problem,unless it cant see the signal when the engine bogs due to the shudder/shake from the bog(i have solid mounts) and is going into a limp mode and thats wat i driving in???, maybe on to something. which would explain the key cycle issue. but the crank sensor threw a code, and this problem started months after the new motor.....hmmm

 

Are all your grounds good on the new motor? You sure you didn't cut any wires(or loose connectors) anywhere

 

i would pull the safc and see if the issue returns.

i had the same issue with my emanage and it turned out to be a loose ign ground. easy fix but i would have never noticed it.

 

im gunna go through my grounds and see what i can find,if nothing im gunna pull the safc out.

 

I would do the same. One little wire could be the difference.

Hope you find the problem. Brian your car is turning into a beast with all the recent mods(with the NOS of course)

Kev helping you out?

Jesse

 

yeah we've been looking at it for the last couple weeks now....


yeah i spent quite a bit of money on it recently,but i figured if i was gunna get a new motor, i might as well get headers and then the list kinda just kept going after that....straight exhaust sounds beautiful.

 

I would say that would sounds like a vaccum issue or you are getting unmetered air somewere. But the whole shutting your car off and restarting and its perfectly fine would make me suspect something electrical as well.

 

tomorrow im gunna disconnect all the safc wires and drive it for alil while...ill update you guys in a-couple days or if the problem comes back

 

I have the same problem with my car. Doesn't happen very often but when it does car shakes etc. I have also found that revving the engine up to 3-5k also corrects it. Still don't know what causes it but i did remove the plug wires one at a time and determined that it is still running on all six.

 

ok so i disconnected the safc on my lunch break and no luck,but i did find something interesting on all data. so they motor i put in my car was from an 02-03 and was only on the road for at max 4months. when we first started it up(after moving the crank sensor) it would not start, so we put my old crank sensor in and it started right up. nows here the thing, theres a recall for the crank and cam sensors on 5th gens. the recall says that if the driver may experience a stallign problem, check engine light or a lack of power. and my crank sensor was bad from the start(on the new motor). so this weekend im going to swap over the cam sensors from the old motor(which worked fine) and see what happens......seems like a good idea to me

 

Sounds like a good plan to me

 

Hope I'm not jumping the gun, but it appears the problem was found and fixed today, props to brian for finding that tsb, I would have never though to check the cam sensors. Resistance spec for cam sensors is all pins (1-2 1-3 & 2-3) is anything except infinite or zero. On the sensors in his car resistance between pins 1 & 3 on both sensors was Infinite, we swapped them with the ones from his original engine; which read a normal resistance value on both, problem appears to be all set.

 

How often was this happening?

Mine only occurs once a week or maybe 2 so it would take a while to know if it was cured. As of right now it hasn't happened for almost a month.

 

unfortunately we jumped the gun, the problem is not fixed


i get the problem at least 1 or 2 times a day, we are going to swap crank sensors with a known good one and see what happens, this is definitely a tricky one.

 

What happens if you rev it up to 3 or 4k vs shutting it off? Just want to know if its the same as mine.

 

the problem wont change by reving it up to any rpm, only shutting it off will fix it.

 

OK its not the same as mine then, either method will fix it.

 

sounds like a wiring problem somewhere

 

Just curious why you think it's a wiring problem somewhere and how that would relate to going away when the car is turned off.

This has been driving me crazy, I rack my brain over it often and I haven't been turning any light bulbs on. It sucks that it's not more consistent (Or bad enough to throw a code to). If it was consistent I'd try to track down a scope and compare all of the cam & crank sensors with and without the problem.

My next steps are to swap out a different crank sensor since his was handled ALOT (though carefully) during the grinding for the 350z flywheel. Go over the wiring near the ecu from when he installed and uninstalled his afc. Wiggle the crap out of every damn wire on the harness with it running, and the ecm relay, fuses, etc. And quadruple check all of the contacts on the more important connectors. if anyone else has any tips or things to go over post 'em up.

I'm thinking two scenarios though, 1: some sort of magnetic feild building up in the wiring for a cam or crank signal, maybe a problem with a ground shielded wire?? Or 2: a magnetized or problem with the crankshaft sensor wheel, which would suck to deal with obviously. But I've really got no idea how I can check for those problems?

If anyone has ANY suggestions AT ALL I would love to hear them, I'm not exactly an electronics expert, just picked up the basics from knowing engines and wrench turning real well.

And yes, Brian has checked/cleaned/re-tightened the timing cover ground screws.

Oh one thing to add though about the crank sensor that had to have it's mounting point fudged with for the 350z flywheel is: Before it was perfectly centered the issue it would cause was a false rev-limit at higher rpms, at higher rpm's it would lose it's signal, car wouldn't rev any higher than xxxx rpm's (as it got adjusted closer it went up), and a code would would be thrown. SO I don't really want to suspect any problems with the crank sensor because it doesn't fit those symptoms at all, I just keep coming back to that in my mind because we had so much trouble with that.

 

so on sunday kevin and i did alot of diagnostics and we might have fixed the issue. known working crank sensor did not fixed it, we thought maybe the variable timing solenoid had clogged (just a thought) so we swapped them,no change. then i had an idea that i think has fixed it. knock sensor. i have energy suspension motor motors and polyurethane filled timing cover and transmission mounts, so im thinking that the vibrations from the motor were causing the knock sensor to pull timing (the knock sensor thinks the vibrations are from the engine detonating), therefore explaining my power loss, and explaining why turning the car off and then on again fixed the problem. which did happen more in stop and go driving(i like to use the engine to slow down alot). ive had about 8-10 key cycles and no issues yet, and i almost always get one per drive cycle. what we did to fix this issue (temp,until i go to radio shack and get resistors) was installing a remote knock sensor taped up in a rag(to help the the vibrations) and i've had no problems yet, ill update if problems come back.