Help with Timing maybe tune?

[Ever]

Just bought a 74 260z with an L28ET swap and an AEM Infinity 3 ECU on top of what appears to be frankensteined with parts from other Z's (280zx,300zx) this makes it a bit harder for me to compare other peoples build and troubleshoot.  Keep in mind the only mechanical experience I have is adding bolt on performance mods and have never taken the plunge into real tuning/modding but I am eager to learn.

 

The issue with the car is that it struggles to start at first but does end up running since I was able to drive it home and take it out on some spirited runs. But if I shut the car off and try to start it back up it takes a while and it wont run properly since it bogs/backfires until I turn it off and crank it again however it idles at around 1200-1400rpm.

 

The tachometer also isn't connected as I cant seem to figure out how since it appears to have an ignition coil from a z31 with a PRW2 and the wiring is different colors than what I have seen online so ill have to figure that out and in the meantime I'm using my laptop connected to the AEM ECU to see where the RPMs are at.

 

Basically I'm asking for help on how to get the timing/tune corrected. From what I have searched I'm suppose to get the car to idle around 750-800rpm and adjust timing to 20 degrees however according to other posts I have to lower the rpms with the ecu instead of a physical throttle screw. It would be smarter to just take it to a tuning shop but Id like to take a crack at it myself. I've already taken screenshots of the tune the way it is as a "backup" before I mess around with it. Do any of y'all have experience tuning with AEM? Maybe see the screenshots for yourself and see if anything is off or can point me on how to at least lower the RPMs so I can set the timing properly. Any help is appreciated. Thank you!

 

Edit: Here is a link to higher quality images.

https://imgur.com/gallery/5sQzZ2D

Edited August 31, 2022 by Ever

[clarkspeed]

Not familiar with AEM. But if it runs ok when driving, take a look at the cold start settings. The EFI needs to shoot a little extra fuel to start, but not too much, and dependent on engine temp.

[NewZed]

Yes, that looks like quite the assemblage of parts.  I think that I see an idle air control valve (IACV), not sure, I pasted it below.  That would be where the idle speed is controlled by computer.  If it is completely closed and the idle is still high then the throttle blade bypass (idle air bypass) might be too far open.  Or you have vacuum leaks.

 

Look at your AEM software for an IACV setting.  You could even just disconnect that hose and block the port to see if idle speed drops.  If it doesn't check the throttle body for an idle speed screw.

 

I wonder what that rubber hose is going to do under boost?  

 

[Ever]

2 hours ago, NewZed said:

I think that I see an idle air control valve (IACV), not sure, I pasted it below.

I do believe you are correct looks like its an IACV from a 90s Volvo. Also as you said I disconnected the rubber hose and the idle dropped to around 750rpm adjusted the timing at the distributer and now its showing around 20 degrees at 750rpm. However the spark timing on the AEM software is showing that it's at 10.6 degrees. The software does come with "ignition sync" im wondering if maybe i have to sync that with the crank so both show 20 degrees?

[Ever]

3 hours ago, clarkspeed said:

Not familiar with AEM. But if it runs ok when driving, take a look at the cold start settings. The EFI needs to shoot a little extra fuel to start, but not too much, and dependent on engine temp.

Here's and image of my "Start" tab in the AEM software (higher quality in the imgur link) im not too sure what to look for but since you mentioned fuel i managed to get my fuel gauge working and went to fill up the tank with fresh fuel and I dont seem to have that second start bog anymore. Car still idles high with the IACV connected and noticed the fuel injectors squirting more fuel at around 30 second intervals.

[Ever]

3 hours ago, NewZed said:

Or you have vacuum leaks.

 

As for vacuum leaks I went around spraying break cleaner in all the hoses I could see nothing seemed to change the idle. However if I press the breaks the idle increases. I'm assuming there's a vacuum leak in my brake booster/master cylinder.

[Ever]

Took it for a test run and the car seems to start up faster and run/idle better with the IACV unplugged. Is it safe to run the car without it?

[NewZed]

22 hours ago, Ever said:

As for vacuum leaks I went around spraying break cleaner in all the hoses I could see nothing seemed to change the idle. However if I press the breaks the idle increases. I'm assuming there's a vacuum leak in my brake booster/master cylinder.

 

21 hours ago, Ever said:

Took it for a test run and the car seems to start up faster and run/idle better with the IACV unplugged. Is it safe to run the car without it?

 

Leaky booster sounds right.  The symptoms fit.

 

The IACV setup on your engine was just an attempt to use the computer to control idle.  Won't hurt anything to leave it off.

 

You need to start reading about aftermarket engine control.  DIYAutotune has some good articles.  Also, the Megasquirt pages.

 

https://www.diyautotune.com/support/tech/

 

https://megasquirt.info/educational/

[Ever]

2 hours ago, NewZed said:

You need to start reading about aftermarket engine control.  DIYAutotune has some good articles.  Also, the Megasquirt pages.

 

Thanks for the tips! I would not of known that was the IACV. I'm just gonna leave it off and plug it with a rubber stopper. Ill check out these pages see what else I can try to do to get it running better.