High idle, Timing jumping up and down!

Basic tech questions such as future setups, different turbo kits, car diagnosis, etc
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Joined: Mon Nov 20, 2017 5:47 pm

High idle, Timing jumping up and down!

Post by tebedatruth » Fri Nov 24, 2017 5:45 pm

Ok, so the basics..1991 s13, Freshly rebuilt motor, 550s, walbro 255, .60 turbo, z32 maf.
Something else that's pretty important is that I pretty much removed all the emissions items, and extra vaccum lines.
I also redid the entire harness, except for some of the engine harness. (it was cut and re connected in some places to shorten/lengthen).

So the symptoms are kinda of strange.. When I start the car it jumps straight up to like 3000 rpm. It will stay there for a few seconds then drop down to like 1500, and then just shoot back up and continue this behavior until I finally turn it off. I have 2 ECU's with Nistune one one of them, so when this is happening I see that timing will go from like 20 to 0 as its revving up and down. If I even touch the gas pedal it will just shoot right up to 2500+ and stay there for a few seconds then continue to jump and lower.

So, I talked to someone in a facebook group who is pretty knowledgeable and he told me it sounding like a huge vacuum leak. Initially this didn't sound correct to me because the rev is increasing and timing is changing aswell (atleast it says it is in nistune consult). But I said ***** it this is my first time rebuilding an entire motor so I borrowed a fog machine from a friend of mine and shot it into the throttle body. I did find a pretty bad leak right by my EGR block off plate, so I separated the manifold and installed new gaskets with grey sealer and retested, leak gone. I was pretty excited and hoped that somehow this was the problem and I turn it on and same thing happens.

So at this point, I'm leaning toward it being a wiring/sensor problem. There has been a lot of wiring **** done and I'm by no means confidently experienced in this field but I took my time and tried my best, so its definitely possible something is loose/incorrect/etc.
What I'm coming here for is maybe some insight as to the components that could cause something like this, and suggestions as to where to start for troubleshooting the wiring. This **** kind of has me stumped at the moment, and I'm just planning on ohm testing all the wires, and checking the reference voltages in the fsm, its going to be very long process so if anyone has suggestions to shorten this it would be greatly appreciated.

Long read I know, but thanks in advance to anyone.

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