High Idle on Startup & O2 Monitor Not Setting – 2002 Discovery 2 w/ Secondary Air

Hey everyone,

I usually post on landroverforums.com, but I'm utterly stuck at the moment and am going for broad reach. So, I'm crossposting this in as many LR forums (and the land rover subreddit) as I can think of out of sheer desperation.

I’m at a bit of a crossroads with my 2002 Land Rover petrol V8 Discovery 2 and could use some expert advice. If I can’t get this sorted, I’ll likely have to sell it out of state since I can’t pass California emissions, which is frustrating because it runs great otherwise. Hoping someone here can help crack this mystery.

The Problem:​

• On cold start, the engine revs up to 2500 RPM, then settles below 1000 RPM after a couple of minutes. This is a new issue that wasn’t happening before replacing the CPS
• The O2 monitor won’t set (all others have). The O2 heater monitor has set, but the O2 monitor itself remains incomplete. This prevents me from passing emissions in California.
• No other driveability issues—the truck runs and drives fine, aside from the high idle on startup. I took it to a local british car shop and the guy there told me that it's just a matter of running through the drive cycles. I've run through them for about 1200 miles and no results.

What I’ve Done (Major Work & Replacements):​

• Replaced:
  • MAF (OEM)
  • IAC (OEM)
  • TPS (OEM)
  • Throttle body (OEM) and valve plate (original was fine but swapped it anyway)
  • PCV valve (upgraded to metal)
• Performed Maintenance:
  • Coolant flush (Zerex G40 Si-HOAT, 50/50)
  • Differential oil change (Valvoline synthetic 75W140, upgraded to brass plugs)
  • Transfer case oil change (Valvoline synthetic 75W140)
  • Brake fluid flush (Pentosin Super DOT 4)
  • Oil & filter change (Shell Rotella T6 Full Synthetic 15W-40)
  • Power steering flush (Pentosin CHF 11S)
  • Replaced spark plugs (NGK Iridium IX) & wires (Karlyn STI 8mm)
  • Installed Extinct's inline 180-degree thermostat (runs about 185ish)
  • Brand new Odyssey AGM battery
• Completed Drive Cycles (Multiple Times)
  • All other monitors have set, but the O2 monitor refuses to.
  • I reset adaptive values **after replacing MAF (**P0101 code persists after going through two MAFs, second one is Bosch), TPS (tried three of them, including a remanufactured one from Rovers North), and IAC (both cleaned the original, and bought an aftermarket from Miami British), and I've completed drive cycles A-D multiple times exactly per the RAVE. I've got them on a clipboard on my dash and have been getting up at 5:00AM and running through them with a timer.
  • Driven ~1200 miles attempting to get the O2 monitor to set.

What Might Be the Culprit?​

• Vacuum Leak? I’ve checked, but it’s worth another round of testing.
• Throttle Body or IAC Sticking? Both are new OEM, but maybe it’s possible something isn’t seating right.
• CPS Wiring Issue? This all started after the Crankshaft Position Sensor (CPS) was replaced. I broke the clip on the wiring harness, took it to a shop, and they replaced the CPS and installed a new wire connector. Could this be related?
• Secondary Air Injection (SAI) Valve Sticking Open? Could be injecting excess air during startup, causing the high idle and preventing the O2 monitor from setting. Anyone have experience diagnosing a stuck-open SAI?
• Long-Term Fuel Trims Out of Range? I'm not sure what I should be looking for to know if that's an actual problem
• Exhaust Leak? A small leak before the O2 sensor could be preventing the monitor from completing.

What I’m Looking For:​

• Advice on solving this once and for all.
• Whether isolating the secondary air system would help diagnose the problem.
• Best way to manually reset TPS adaptation (beyond just resetting adaptive values).
• Insight into whether the CPS wiring could cause these symptoms.
• And possibly most important: If you know the best LR technician in the States (yeah, I know it's a longshot) and that person happens to be somewhere near me (I'm in California USA half way between LA & San Francisco), a referral.

Plan B – Selling the Truck - which I'll have to do in the US.​

Thanks in advance!

As I mentioned, I'm gonna cross post this on a couple other forums for maximum visibility.