EFI High Idle Issue

[KyleQ]

Background - I've got everything hooked up off a series of switches, the only thing the factory key does is turn the alternator charge function on - just the way it worked out. O2's are not hooked up, have not mounted them in the exhaust yet - on the list for tomorrow.

The Bronco starts great- idles perfectly, the issue is when I give it some throttle the RPM's race up and sit there, like the throttle is stuck open. I'm wondering if the IAC is sticking or if it's because of the O2's. I did some work trying to get the throttle body rotated so the IAC is on the back, clearing the hood was what I was after.


The IAC controls idle, I know the throttle plate is closing. If it is sticking open that would explain the idle issue - just curious if it's the O2's or something else...

I need to check TPS voltage (which is new) and test the IAC - I'm thinking my issues are there. Starts fine, idles great and goes into lots of RPM idle (no tach) and sits there until I reset everything...

 

[DirtDonk]

Nice looking setup you got there.
What ECM are you using? Matched to the components?

Also, your PCV return air is not hooked up. That's right there where the idle action is, so this could be a culprit I would think.
Do you have a PCV valve in the back of the intake hooked up to manifold vacuum through the upper plenum? If so, that's correct. You just need to connect that rubber hose you have running from the Throttle Body to the hose fitting there at the oil-filler neck.

Good luck. Hopefully that will at least have some minimal positive effect.

Paul

 

[KyleQ]

Thanks-

That is an old picture trying to show the throttle body - I'll update this with a new picture soon. The ECM is matched to the harness and motor, everything is 87' Mark IIV.

 

[KyleQ]

More updated stuff-

I don't think I have any vaccuum leaks, I wrapped the pcv holder once with electrical tape when I replaced the PVC and pushed it into the intake. Everything else is plugged - the IAC plug was cut off, maybe I wired it up backwards... or have the TPS on backwards..

 

[bluesbish]

I am thinking you have a large vacuum leak or a TP problem. TP will usually cause this symptom, but like you said it is new. I think some were adjustable which is probobly why you were talking about checking voltage? perhaps you have a vacuum leak at the throttle body gasket since that is where you were trying to make clearance. running everything off of a series of switches, are you cutting off KAM power to the pcm everytime you shut the system down? this would create a situation where the pcm was trying to learn idle strategy and fuel trims all over again everytime you start it up. without the O2's hooked up, you are running in open loop, so everything is pretty much preset at that point. I would get the system completely buttoned up, make sure you have a KAM power circuit, and let the thing run and learn and see what it does from there. Do you have your cooling system installed at this point? A good, accurate ECT reading is very important on startup and while running in open loop.

 

[KyleQ]

I am SO glad I take pictures of everything-
IAC pointing this way-


IAC pointed the OPPOSITE direction-


We just had to think about this for a second - how this thing actually functions. The way we had it setup, and how it was intermittent and the kicker, it idled great until you gave it throttle, creating a shitload of vacuum and it basically wedges it open and the motor races.

We rotated the throttle body, completely screwing my throttle linkage, put it together and fired it up, idled high for a second and dropped right down. Throttle response is immediate and fast -


Now bluesbish, your point, and I have been thinking of this. I DO kill the ECU every time I shut the ignition off, I've got two wires I hooked to constant power - one was labeled 16v start and the other was just power. The power wire joins up in the harness on the relay side, including direct output power form the alternator. I'm guessing that one should be powered on at all times and the 16v start can come on with the key.

Does that make sense?

It's going to snow ~5" tomorrow night, I'm going to fix my throttle and get out there and do some serious "testing" ;D Maybe I'll get the Go-Pro out for some action video...