Datsun Roadster Forum-311s.org

Researched the Silvia forum. It behaves like it's missing the Start Signal to the ECM on pin 34. I'll run that down next.

Well I do have a start signal on pin 34 and I confirmed with Nistune consult that the start SW bit goes high when I start cranking. Need to look elsewhere

A missing start signal wire will usually mean that it will crank (but not fire) for longer than usual until it finally catches.

You never did confirm that you have the tube for the AAC valve connected to the intake plumbing before the throttle body.

Do you have 12V+ key on power to the AAC valve (I believe the B/W wire)? The other wire is SB (Sky Blue), make sure you have continuity to the ECU....

Michael,

Tube from TB to AAC valve is indeed there. I'll check voltage to AAC valve but I thought the AAC valve was pulse modulated. I can see the AAC valve counts changing in consult an it closes down airflow and idle rpm as things warm up. I'm thinking it's working as intended but I will research it more. Definitely an odd idle control system with that goofy system up on the TB cam that changes position is the TB gets warmed up by engine coolant.

I did look very closely at all connections to TB and Plenum. I did indeed find one of the small vacuum tubes under the TB was open. I thought for sure that was the ticket. So I plugged it and retested. Problem still exists. Rats

The large tube under the intake near the throttle body goes to the IAC
It needs to have a hose from it to the intake tube before the throttle body.
The IAC bypasses air between the 2 butterfly between them.

Why not install a catch can system? It adds some complexity (especially with space restrictions) but can make a huge difference in reducing the amount of oil going into your intake system.
The website here: https://damondmotorsports.com/blogs/dam ... ye-blow-by
describes a number of different set-ups with pros/cons and applications. Some configurations can add unmetered air to your engine, some don't.

I recently modified my mazdaspeed 6 and what a difference!

Good luck!

Kevin,

"It needs to have a hose from it to the intake tube before the throttle body.
The IAC bypasses air between the 2 butterfly between them."

Here's my IAC tube


IAC valve


BOV


Still behaves like that start signal. It's cranks for a good while before it fires, then runs on 1 or 2 cylinders for about 5 seconds or so. Then it catches and purrs like a kitten. I assume the Start Signal (pin 34) is only supposed to be at 12V when the motor is cranking (key turned fully clockwise)??

BTW- Kevin, I'm probably out of the loop on this but I stumbled across your SEMA video. Very cool indeed - congrats.

Thanks to all for you input.

Regards,
Steve

I don't know the SR20 EFI system, does it have a start enrichment system? Mine has a programable enrichment during cranking.

Phil,

In looking through the Nistune tables it does appear that there is a start enrichment table. I haven't messed with any of the fueling or timing tables at all yet. The motor is bone stock (except for the log header and FMIC and air induction system. I would have expected it to behave pretty well with the stock fuel tables. Maybe it's time to dump some fuel to her and see what happens!!

Regards,
Steve

Thank you on the SEMA deal.

Ok I need ask a stupid question.
Is the plug on the ECU tightened all the way and pushed in on the edges.
I have found this on other builds.

This is back from the dead. I had disassembled the whole car for paint, and now I'm reassembling. I was trying to fire it for the first time but wasn't sure if I was having an ignition or fuel issue. So I pulled the PVC hose off to squirt some fuel in to the intake plenum. Lo and behold, The previous owner in Japan put a homemade restrictor plug down in the PVC hose. So I'm thinking with that restrictor, the airflow direction was out of balance in the crankcase and the MAF was totally confused. So, I'll remove the homemade PVC restrictor, and reinstall the stock orifice restrictor in the hose from the valve cover to the cold air intake and see if that solves my never ending startup stumble. I'm guessing yes.

I was a fuel issue BTW, I had the lines reversed at the tank. It's alive!!

Regards,
Steve

Well I'll be darned! That was it. The restrictor in the PCV hose had about an .080 orifice. Definitely was a crudely made homemade piece. I yanked it out, put the stock restrictor on the hose that runs to the intake pipe, and no goofy stumble at startup. I guess that's par for the course when working on stuff where the PO thinks they're smarter than NISMO.


Many thanks on all of the suggestions. It's getting closer.


Regards,
Steve