Help! M50nv Not running right.... at all.

[Vtec?lol]

Hey guys, I've been working on this swap for a while now but It's not looking too good.

At first when I started the engine it would come on and idle great and stay at 8k but I never let it run for more than 10seconds at a time since I don't have a puller fan.

When I finally got the balls to start it and give it a rev it would bog down as if it weren't getting fuel but then it would go up to about 3k and rev fine and then it cuts as if you turned the car off and then revs back up to 3k and cuts again.

I installed a Y-pipe to hook up my o2 sensor and still nothing. I disconnected the Throttle Position Sensor and played with it while running but the engine acted as if it weren't even there. it also runs the same without it plugged in at all

here's a quick vid


Someone help please.

Thanks cheers!

[trackjunkie21]

check MAF direction.

[e46s54dr]

Kind of a wild guess but is the maf sensor flowing in the right direction? There should be an arrow which points to the way of the air flow.

[e46s54dr]

check MAF direction.

Beat me to it! lol

[e46s54dr]

Also, I f you disconnect the tps and see zero changes, it might just be a faulty tps.

[nrubenstein]

First things first as long as there is coolant in the system, you can run it in place for several MINUTES with no cooling fan.

If it runs like this without the TPS, then it's unrelated. The car will run acceptably with no TPS.

I'd look at engine ground connections, your CPS, and anything else that could be loose for starters. If you can pull codes, you should do that too.

[Vtec?lol]

Thanks guys! Everything is grounded. Air flow is in right. Any other ideas?

[Vtec?lol]

It's as if I have a revlimiter at 2500rpm.
This is killing me because if it were an m20 I can go down a list of things and fix it but this is a different breed of engine lol.

I can't pull any codes and the stomp test doesn't work.

Is there a way to read codes or put a jumper in the diagnostic port?

I have a week to get this car on the ground and it seems like the longer it stands the bigger the hole gets in my pocket.

Thanks for any help cheers. :(

[e30rapidic]

are the crank sensor and cam sensors connected to the wrong plugs?

[Vtec?lol]

no, they are in correctly. I would go swap them around to check but I'm assuming if it's anything like the M42 it wouldn't even start if in wrong.

If I leave the ECU/DME unplugged for a while and start it up, I can hesitantly rev it all the way to 4k, then it revs up to 6k smoothly. try to do it again and i get a no go and it starts cutting again at 3000rpm max. THE FRUSTRATION! lol patience my young fellow.... I practice le patience.

[jrdeamicis]

You really need to get an oscilloscope on your crank signal. OBD1 uses a VR sensor and when it starts dying it can be intermittent.


Unplug your MAF and see if its a mixture issue w/ the maf.
Restore MAF
Unplug O2
Restore
Unplug Cam
Restore.

Each one of these will help you diagnosis what your issue is.

[Vtec?lol]

Thank you for your help. I'm going to swap crank/cam sensors now. I'm getting back fire in the intake or preignition so i'm scared to run it.

*edit found water in the plug valleys and sucked it dry then replaced plugs and coils and now it's running worse.
Unplugged the TPS = no difference
restored

Unplugged the o2 = no difference
restored

unplugged the maf and very litte difference. I can't figure out why it stopped idling after leaving the ecu unplugged

[Vtec?lol]

Hmmmm. Stomped, bump?

[SamE30e]

It's as if I have a revlimiter at 2500rpm.
This is killing me because if it were an m20 I can go down a list of things and fix it but this is a different breed of engine lol.

I can't pull any codes and the stomp test doesn't work.

Is there a way to read codes or put a jumper in the diagnostic port?

I have a week to get this car on the ground and it seems like the longer it stands the bigger the hole gets in my pocket.

Thanks for any help cheers. :(

Check the tps with a multimeter. The car will run without a TPS, but it can be a combination of things. Also if the cam and crank sensors weren't hooked up properly the car wouldn't start. Make sure you didn't mix up the cam sensor with the ICV. That's also possible.

It can also be a bad MAF, try and get your hands on another.

Figure out the stomp test first, it can be the key to what you need.

[nrubenstein]

If the diagnostic port doesn't work, then you haven't wired up the harness properly. Pin 16 on the diagnostic port needs switched power. IIRC, this comes through the X20, but it's been a long ass time so I don't remember. Or you can half ass it with a jumper.

(Note that a lot of adapters do not power the port.)