Air Flow Fuel Injection System issues with my Datsun 1977 280 Z

GTOPieter · April 10

Hi folks,

Please bear with me I am not and expert so I am trying to learn more about my set up and issues

I am having an air flow and fuel mix problems in my car. The motor and fuel injection systems have been modified. I am having fluctuation with my idle, especially after the car warms up

Initially when it is cold the idle is at about 800-1000 but revs increase when the engine is hot up to about 2100

We have established there are no vacuum leaks

The car has a modified fuel injection system and apparently a Megasquirt 2 setup?

I had the car checked by a mechanic from Nissan who has a 280 Z and here is his reports. I posted his report on Zcarforum and got some more offers of advice ( see below)

Verified concern idle hang when the car reaches operation temperature. Found that the car has an aftermarket intake system converting to individual throttle bodies. Concern is similar to symptoms shown from a failing boost-controlled cut device. Failed BCDD will cause the idle to hang, due to the diaphragm expanding to hold throttle plate open during decal for emissions purposes>BCDD is mounted to the throttle body which has been removed for ITB setup. The car is also running a stand-alone ECU which may have been having tuning issues causing idle hang

Responses

well looks like the BCDD which is known to cause problems as described is not the problem, since it was deleted. With aftermarket mods its going to be tough to give any answers. Only thing I can think of is a mechanical linkage issue unless you have some kind of vacuum leak going on. Could just be leaning out, could be an ign advancing, who knows.

You have a highly modified 280Z. You need to find someone who knows how to tune a Megasquirt system with individual throttle bodies (ITBs).

It sounds like you may need to start rooting around to learn about the parts you have in your car.
Two sources:
1. Megasquirt's website: MegaSquirt | Premier DIY EFI Controller
2. HybridZ.org (HybridZ) If someone has performed a unique modification to an S30, it's probably documented here. Do searching and reading before asking questions. These guys are self-taught and don't take kindly to people looking for hand-outs. You should might also want to search for ITB on that site to see if you can find what type ITBs you have. If you can find out more about the ITBs, that could give you a clue

Of course, I'm just focusing on the heart of the modification. Don't forget to check the linkages from the gas pedal to each throttle body. Look for slop or binding that could prevent the linkage at the throttle body from returning to idle position.

By the way, I did just notice something. There is not a heat shield between the intake and exhaust. That is definitely NOT going to help the performance of the engine.
I posted a photo of my engine bay. You can see how I crafted a heat shield to keep the heat from the headers from impacting the throttle bodies directly.