It’s open I added a video. Once I get home again I’m going to try testing with a battery to see if the ISV is bad and maybe swap the original back in

 

And you say it did this with the old DME too? You might try removing the connector from the DME and ISV, and make sure you don't have continuity (short) between any of the three pins on the ISV connector, or between any of those 3 pins and ground.

 

I had this exact issue which was solved by having my DME "repaired" by Focus9. It's basically a new board. I even tried soldering new transistors into place. However, I agree with Tom, I would check your wiring for continuity issues. Make sure you shake the harness and see if it changes.

 

It sounds to me like you have a bad TPS idle switch. Unfortunately the turbo’s TPS is unbelievably expensive now. A 30+ year old potentiometer w/idle switch does go bad. Even if you hear the switch “click” at the idle position it can still be bad. Maybe Tom can start making them for us all at a decent price with his 3D printer and mad skills.

 

Not so sure about my mad skills but thanks I imagine it would be easier to adapt a similar TPS to our TB? Are TPS's NLA (again)? I thought I read that they came back?

In any event, see the OP's post #5. The bouncing stops when he pulls the TPS plug, and the rpms go up to 2600 and stay there. That would make me think the TPS idle contact is working. It's got the air for 2600 rpms, but when it gets to about 1600, the DME cuts off the fuel because the TPS idle contact is closed, then when the gas is turned back on, the cycle repeats. Puling the TPS plug removes the TPS idle contact and the DME over-run fuel shut off, so the rpms just climb up to wherever they want... Or am I missing something?

 

Yeah that’s sounds right. For the moment I’ve just plugged off the ISV and the car runs fine, rpms are pretty low till it warms up

 

Ah, I had understood you to say in post #5 that the idle still bounces when you pulled the connector off the ISV. If it actually smooths out with the connector removed and hoses still connected, then I'd go back to suspecting your DME (however new) in addition to the harness and ISV itself.

 

No it does still have the same condition with the ISV unplugged. For some reason it’s staying wide open when connected, still need to test for continuity. I blocked off the hose going to the hard pipe and plugged the hard pipe hole for now.

 

Got it. Since the DME is new, I'd suspect the harness and that repaired connector. I'd be inclined to run my own temp wires to the ISV to see if you can get it to behave (and essentially confirm something is going wrong with your current wiring....). Lindsey sells a patch harness for the ISV if it comes to that, although fixing your existing harness should be doable too if needed.

 

One other ISV tip is that this DME control circuit runs as soon as you turn the key to the run position, i.e. you don't have to start the engine to test it. If it's working right, the DME will be flipping that valve open and closed about 100 times a second. It vibrates the valve enough that you can feel it. It's an easy check when the ISV is still under the intake and all the hoses are hooked up.

Be careful when probing the ISV wire harness connector when the key is on. If you accidently short pin 2 to pin 1 or pin 3 you can blow the transistors inside the DME that operate the ISV. There is no protection on this circuit. The transistors need to see the impedance of the valve solenoids in order to limit the current switched through them. If the insulation on your wires behind the strain relief boot are cracked and exposing bare copper this may have already happened.

 

Good info. Since he had problems with the connector and had to re-wire it, you have to wonder if that's why his nearly-new DME is acting like it has a blown ISV driver...?

 

Okay so with the intake port and hard pipe blocked off and idle set to ~840rpm at operating temp I’m still only getting 12 InHg of vacuum. I can hear the air hissing around where the AFM connects to the j-boot. It gets slightly louder and cuts off right away when revving the engine. Another hissing also starts if I start to unscrew the idle screw (not sure if this is the same source though).

I tested for continuity with my multimeter and the read out was zero with no noise from the ICV connector to the DME connector for both pins. When I connect any of the ICV pins and chassis ground there is no circuit for any of them. Does this mean they are not grounded or is it normal?

 

I opened up the DME and took some pictures of what I think are the transistors for the ISV (4 of them not sure which pair are for the ISV). The contacts look good, I assume you can’t tell if they are blown just by looking at them.

Also I attached a video of the air hissing.

 

Jacob,
One of your videos showed the ICV was not operating. You still haven't figured out why.

Checking for continuity where it's supposed to be is good, i.e. ICV 1 to DME 34 and ICV 3 to DME 33 (assuming that's what you did) but that does not tell you if they are shorted to each other (ICV 1 & 3) or to pin 2 at the ICV connector.

Make sure the DME and ICV are disconnected from the wire harness. With your ohmmeter, check for continuity between ICV connector pin 1 and 3. There should be no shorts, i.e open circuit. Wiggle the connector a little while you are measuring. Now check between 1 and 2. Should be also open circuit. Now check between 2 and 3. Should also be open circuit.

Now check for +12V at the ICV connector. Set your meter to measure DC voltage. Turn the ignition key to the run position. Measure between ground (at the - battery terminal if possible) and pin 2. Should be +12V.

Report back on that and let's see where you're at.

I can't recall if you verified that your ICVs work independently following Tom's test procedure video. You need to do that as well.

BTW, it is normal for none of the ICV pins to show continuity to GND with or w/o the DME connected assuming the key is turned off. I've not seen a schematic of Joe's DME so I can't say how he handles control of the ICV solenoids.

 

Open circuit between all ICV pins and 12 volts from pin 2 to the battery ground.