High idle

wilsonsandy07

Member
Aug 7, 2019
10
0
las vegas
After a simple fan clutch change I just happened to have a valve cover gasket go bad. So I disconnected the coolant lines and pcv valve, swapped out the gasket and refilled and bled coolant system, but now I have an idle around 1500. it was definitely lower before hand and I don't want to stress anything out more than it needs to be. Does anyone have any input into what might have affected this? Its got to have something to do with what I changed, the odds of the idle just randomly going up are pretty low. Can anyone help?

97 discovery 1, v8 4.0 175k automatic
 

bradartigue

Well-known member
Mar 7, 2018
112
16
Sandy Springs, Georgia
You've most likely created a small air leak. Above you note the PCV valve, check the plumbing to and from the valve and any other air hoses or ports you may have disturbed. When I first received my 2000 it was idling a little odd and throwing codes indicating the mix was lean. I was stumped until I found the small air port by the brake booster hose had a crack in the bottom of its cap. It was a small crack but had a large effect. I've worked with a lot of fuel injected cars and find the Discovery, at least the Discovery 2, is hyper sensitive to air leaks.

Easiest way to find an air leak is to use a can of plumber's propane. Don't light the propane, just let some bleed out while moving the tip around air hoses and joints. When the engine speed increases (due to the ingestion of a little propane) you've found a leak. Other stuff works as well, like starter fluid sprayed in short bursts, but it can get messy.
 
  • Like
Reactions: michaels

discostew

Well-known member
Sep 14, 2010
6,417
497
Northern Illinois
You might have either created a vacuum leak like was mentioned. Or you could have disturbed the throttle cable at it's mounting bracket. I would think you would hear a vacuum leak that would raise the idle to 1500 rpm. so look at the throttle cable, it has a black plastic adjuster wheel on it for raising the idle while winching.
 

Trent and his Rover

Well-known member
Jun 25, 2006
124
1
Simple quick test for vac leaks:
1. Open hood
2. Start Rover
3. Spray some carb cleaner around top while engine runs
4. If there's a leak, she'll suck it in and her idle will surge.
 

discostew

Well-known member
Sep 14, 2010
6,417
497
Northern Illinois
Stew not being a smartass but is the adjuster wheel specificly designed for winching application if so thats a hell of an idea
It wasn't my idea. They all have the shit. But it also gets bumped sometimes and you have to wiggle it a little toget it to fall back in the bracket. Then the idle drops back down.
 
  • Like
Reactions: best4x4