Question about TPS operation/idle quality on my new engine
07-27-2016, 11:27 PM
#16
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The harness is hacked to pieces. *sigh* I really hate the PO of this car. I'm just going to delete the ISV for now because I think its the best solution at this point and will result in the car running better.
07-27-2016, 11:53 PM
#18
Rennlist Member
The ISV has three pins in the connector. The middle pin (pin 2) should have 12 volts. The DME pulses pin 1 to ground to move the valve in one direction, and pulses pin 3 to ground to move it in the opposite direction (i.e., one pin to open the valve, one pin to close it.) You can test an ISV with two alligator clips and the car's battery. Connect the middle pin to the positive terminal of the battery and then tap one of the outer pins to ground and the valve to snap to the open or closed position. Then tap the other outer pin to ground and the valve should snap the other way. (Don't let the ground hit the hot #2 pin of course!)
You should be able to confirm or rule out the ISV as the source of your high idle easily though -- just remove the hose going to the i/c pipe from the ISV and block off both both the hose and the pipe (or put duct tape on the i/C port to block it, and put the hose back on. If you physically block off the air path from the ISV and still have the high idle issue, then air is getting in somewhere else. If blocking it off solves the high idle, then it's either the ISV itself (which you can test per above) or the driver in the DME...
You should be able to confirm or rule out the ISV as the source of your high idle easily though -- just remove the hose going to the i/c pipe from the ISV and block off both both the hose and the pipe (or put duct tape on the i/C port to block it, and put the hose back on. If you physically block off the air path from the ISV and still have the high idle issue, then air is getting in somewhere else. If blocking it off solves the high idle, then it's either the ISV itself (which you can test per above) or the driver in the DME...
07-28-2016, 12:23 AM
#19
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Ouch! You'd have to really work to eliminate the junction box and still have a running motor. Can't imagine what would motivate someone to do that... In the meantime, you can always tap into the 12v to the injectors and run that to the center pin of the ISV to replicate the factory wiring....
07-28-2016, 12:58 AM
#20
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I had to rebuild the injector harness to get it running. I thought about jumping power, only question is; do the groun signals from dme pin 34 and 33 also run through the junction box harness or would those still presumably be intact? if so, running 12 volts to the connector is no big deal. if the wiring to the dme is also compromised, it'd be too much work to fix after all ive just done and i'd rather delete the isv.
07-28-2016, 02:42 AM
#21
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Any idea what color the power wire to the ISV is? I'm going to try giving it power from whatever 12 volt key on source I ended up using to get the fuel injectors working.
07-28-2016, 12:05 PM
#22
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It's blue with a red stripe. I'd just cut into the harness a few inches away from the ISV connector and cut the wire going to the middle pin, and connect your 12v source to the wire going to the connector. If you still don't get 12v going to the middle pin, then check under the rubber boot for fray/disconnected wires.
07-28-2016, 04:34 PM
#23
Three Wheelin'
By the way, LR makes a replacement for the ISV harness. It includes 4 or 5 other connections too (temp sensors, oil level etc.) It's separate form their injector harness. I have it on my car.
07-28-2016, 07:31 PM
#24
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Why not just bypass the ISV? I did and it runs better than ever. I also deleted the venturi and auxiliary air valve. Starts up great and idles fine cold. I could see nursing the throttle for a few seconds if really cold out. At least try as a temporary set up then decide.
07-28-2016, 07:57 PM
#25
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Another alternative, what about using the early idle control valve? You may have gotten one on the early engine you installed. It gets switched +12v and a ground and would install directly in place of the late ISV. There is even a pin connector (unused) on the late harness that it can plug into.
08-05-2016, 12:41 AM
#26
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just to bring this to a resolution; I deleted the ISV. It was indeed stuck open in the last position it was in when it actually had power, bypassing too much air for a warm engine causing a high idle and low vacuum. idle is now 1025 rpm and it pulls 20" vacuum. Cold idle is ~900 and does not need any throttle input to idle smoothly from a cold start.