Hi all. This is about a 1997 Discovery. It was running fine until when out on one trip I put it in park. The engine revs shot up to over 2000.
I have since been through the MAF, IACV and TPF. One vacuum hose has been replaced; the one at the plenum next to the IACV.
While I can't hear any air "sucking" sounds (my ears aren't the best - too much rock 'n roll) I keep seeing references to how it can be a vacuum leak. The problem is, what to look at.
Where can I find a map of the relevant vacuum hoses that I need to look at?

 

I had the same issue with my '99. It was not a vacuum leak. You need to modify your throttle position sensor so that it reads a value closer to 0% when the throttle is closed. This is done by drilling new holes so that you can rotate the sensor just enough to lower the idle. You can check the value with a scanner. I had a thread on it a few weeks ago.

 

Thanks for that. Do you know what caused it to "go out"? Also, do you recall which direction you rotated it in?

 

I bought the truck with the high idle and judging from the service records, it's had a high idle for years. I rotated the sensor clockwise.

 

Theoretically you could just unbolt the tps, harness still attached, start the truck, and turn the tps manually to observe idle changes, right ? If so then making a determination if the tps is the issue? Makes sense in my head, but my head needs its tps adjusted too, so...

 

I wouldn't really suggest rotating the TPS as the best method for adjusting idle speed, resetting the adaptives is how it's technically done and with robertf's file floating around (hhoward's threads) there is no reason to mechanically do so. The ECU adaptive reset will assume relaxed throttle position is 0. Also it will reset and adapt the IAC to correct idle setting which is the reason the idle is high..... sheesh.

 

2nd that - its the only thing that fixed mine
https://discoweb.org/showthread.php?...GH+IDLE&page=5

 

Robertf's program did not work for me. Tried it a bunch of times, on other trucks with a variety of computers and it just never worked. If it does work for you, then I guess that's your solution.


For me, modifying the throttle position sensor worked perfectly. Nothing was wrong with my IACV adaptive values or the IACV itself. I have no complaints.

 

**UPDATE** found a local garage with the right LR tools to scope the engine. His fancy computer would not connect (communications error). He said it seems like your engine ECU (ERR7377) isn't working right. We pulled it out and sure enough the bottom of the unit is almost rusted right through. Have yet to open it up but I think I know what I will find. Now I'm on the hunt for a good/used engine ECU. May God have mercy on my soul lol

 

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