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Discussion Starter · #1 ·
Hello! My name is Michael. I'm new to the forum, and Land rovers. I recently purchased a 1998 Disco 1. 128k miles. 4.0L The truck has been sitting for about a year, being periodically started. I was told it had a "new" engine installed a year ago. Anyways, when i start it, it revs to 2000+ rpm. Sometimes it will drop to 1500. I replaced the IACV. Couldn't find vacuum leaks with starting fluid method lol. No check engine light. Cleaned MAF. Replaced battery. Cleaned throttle body. Has a small exhaust leak at the manifold gasket on passenger side. My brother bought a tps but its the square style for the MK2. It wouldn't work would it? I actually got it idleing at 700 rpms using some method to reset the iacv but when i started the disco again it wsnt back to high idle. ??? Can someone help? Should i have kept my money?
 

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Discussion Starter · #3 ·
UPDATE: Key on
Wait a few seconds
Key off
Wait a few seconds
Unplug IACV
Key on
Wait a few seconds
Plug in IACV
Start
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If i turn it off and start it afterwards the idle is back around 2000. ? It's a new IACV. Do you think i just need it flashed? It seems like the computer doesn't know when or how far to adjust the IACV. That trick i did tells me it opens and closes. Key off seems to close and key on seems to open.
 

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Hey.
I.a.c. Motors are an output only unit with no feedback to the computer. They do not require programming

Do you have access to a scan tool that reads engine data (not just a code reader) ?..
You should be able to look at desired idle / engine speed in scan data. This will be an indication of whether the computer is commanding high idle or whether it is unable to control it.
Another thing you could try if you don't have a scan tool is blocking off the tube between the I.a.c. And the intake , you should get a
Low idle (probably 500-600rpm. If you do it is either a defective /bad I.a.c. Or a control /computer problem.
Is the new part an aftermarket or a proper original equipment piece?
If you still have high idle, it is drawing unmetered /uncontrolled air in somewhere else (you have a leak)
Hope this helps
Let us know how you make out
 
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