A/F goes up and down at idle and wont hold a consistant RPM

[j87w]

The setup is a 90 240SX w/ AEM EMS (Speed Density Conversion, 3.5BAR AEM MAP Sensor, AEM IAT). It also has Tomei 740cc injectors for fueling. All parts are brand new and the engine has just been rebuilt. I have tried changing the plugs, new air filter, checking all vacuum lines (all hoses are brand new and gaskets). What happens is the engine idles OK when cold but as soon as it warms up the idle stays fairly consistant 800-950 RPMS but the A/F starts bouncing from 12.5:1 to 17:1, back and forth. Also if you try to rev it up, say to 2000 RPM's the car will hold 2000 for a second then it will start going from 1500-2000. If you try to rev it any higher you can hear it misfire. The WB02 gauge matches the AEM Screen. I have tried setting the injectors from 680cc to 800cc and nothing helped there. I have checked the TPS voltage (its correct at .44V). I matched the ignition timing (crank to screen), idles at around 21-22 degrees of timing. I have tried upping the idle from 875 to 950 and nothing. I also tried disconnecting the IACV to see if it was going crazy but it did the same thing. I have some logs of it but Zilvia wont let me upload them. Any ideas?

[j87w]

I turned off fuel learning and it stabled out the A/F ratio. But it still does it! I logged my ignition timing and now it started bouncing up and down (on the screen and on the crank) from no less than 7 degrees up to 28 degrees (at idle) just back and forth almost instantly. I tried to see if I could lock down the ignition timing again but it just goes all over the place when you try to time it.

[slider2828]

Sounds like a vacuum leak.... Also check the Coolant temp sensor....

Also this is an AWESOME trick thanks to steveshadows who knows our motor like the back of his hand...

Close the IACV and open the throttle screw a little.... On the throttle cable half moon, you will see a little screw make it keep the throttle open a little more and compensate with the IACV screw...

Also check for Vac leaking, sound like a vac problem.

[j87w]

It has nothing to do with the idle speed. It will pretty much hold a consistant idle (900 RPMS or so). It will hold a consistant RPM when you rev it up and hold it (say 2000 RPMS). Its just that when the car is warm and it trys to idle the ignition timing base map calls for 21 degrees now. At first I logged RPM vs. WB02 vs. Ignition timing. Everything was fairly steady at idle (rpms bounced around a bit) but the A/F would go everywhere. Now the idle and A/F are really smooth but the ignition timing is going everywhere. The car idles at like 8 degrees then it starts bouncing up and down. The coolant temp sensor works just fine. I have checked it by watching coolant temp. My first thought was it was a vacuum leak also. But I have all new hoses, couplers, clamps, gaskets, and I have sprayed carb cleaner near everything IM related and absolutly no change in idle whatsoever. I dont really understand it but I went back to the old map and it the A/F ratio is fine now but the ignition timing does the exact same thing.

[j87w]

I totally forgot about the ignition comp tables for rpm (they would add or subtract 15 degrees of timing for a slight change). Once I zeroed the table for that and the one for fuel and readjusted my base map for fuel the car ran 10x better. I didnt think the AEM even had a table like this.