By greg sparhawk on Tuesday, September 04, 2001 - 09:28 am: Edit

so hear is my quandry.
in gear, moving, the idle revs up to around 2k rpm...when i stop, after a second or two, it drops back down to around 750 rpm. i also heard a knocking sound. both went away yesterday and teh rev'ing has returned today. any ideas?
current issues with my otherwise incredible rover:
just replaced the drive belt, about a week prior to noise.
oil pan seal leak
rear main seal leak
oil level is alright however.
any help would be much, much appreciated.
thanks in advance.
greg

By Series III on Wednesday, September 05, 2001 - 04:31 am: Edit

Welcome to Roverhood Greg......I am lucky if my Disco dont choke down while sitting at a light. Buy yourself a Haynes manual and it should show you where you can adjust the IDLE. KNocking Sound? I have no idea what thats about

By Daniel on Wednesday, September 05, 2001 - 05:06 am: Edit

Greg,
Something to think about may be the throttle position sensor. It has been written up recently and is supposed to be a cheap fix ($75 or so). I think I might be due for one soon.
My idle will rev to about 2k when starting and a quick blip on the throttle will settle it back down. Also, I have had two recent episodes where the truck will momentarily loose power at highway speed then pick back up.
Does this sound familiar?
Does the idle problem coincide with the knocking, or is in unconnected?

By greg sparhawk on Wednesday, September 05, 2001 - 09:20 am: Edit

some interesting things going on.
we had the oil changed yesterday and they ran a cleaner through for about 15 minutes, then new oil. we put in a gas aditive, thinking that might help...to no avail. the reving and the knocking both started at the same time, but i can't find any connection between the two. the knocking will start up quietly then progressively get louder to a tapping level (not too loud, but certainly noticeable). if i shut off the engine, wait about a minute then start it back up the tapping is still there, but it gets quieter then goes away for about 30 miles.
i wouldn't bother everyone with this, but i live in the rockies and am not very close to a good mechanic (that i know of).
thanks on the throttle/idle advice!

By greg sparhawk on Thursday, September 06, 2001 - 04:53 am: Edit

heres the update for anyone willing to help
definitely a trend. when i turn the truck off, then back on the tapping goes on for about a minute then goes away, only to return after 15-30 miles.
rocker arm?
oil pressure?

By mike on Friday, September 07, 2001 - 02:29 pm: Edit

I have seen many a misrouted acc belt reek havoc with a disco. If it is running from the alt to the ps pump it is routed incorrectly. hope this helps

By tmsltd on Tuesday, September 11, 2001 - 12:15 pm: Edit

I have another bit of advice. Could the knocking sound be eminating from the right hand catalyst in the exhaust pipe? It is common for them to become loose and rattle with varying engine speeds and temperatures. Also, as far as idle speed control, the Idle Air Control motor is a more likely suspect than a Throttle Position Switch. The IAC is a Chevy part that is available from NAPA or other national parts retailers. There is a method for setting the base idle (the speed that the engine would run if the IAC did not control LOW idle speed) but it requires a tool that a Chevy/domestic shop should have.
A test for the catalyst is too use a long screwdriver, rest it against the catalyst and listen for a rythmic sound at the exhaust pipe. The solution is to upgrade to an NRP high performance cat from Rover's North!
Good luck