1999 D1 SD, 4.0/auto
In the seemingly neverending saga of what's wrong with my Rover, I've recently taken care of some things, and some new issues have developed. It's sat for a little over a week as I've been busy, and didn't want to drive it with the fuel leak being as bad as it was.

I put a new fuel pump seal in, so no more gas leak! I'm still seeing P1447 and P0451 pop up as pending codes, but haven't driven it enough yet to see if they'll set a hard light.

Now with everything warmed up when lightly accelerating from a stop the transmission seems to jump in and out of gear a couple time before it settles in and drives off, and the shift into the lower gears when coasting to a stop is more noticeable. I wouldn't say harsh, but it alarmed me somewhat. Having worked in a transmission shop for a few years, I'm very distrusting of autos, so every little thing catches my attention.
Edit: I just did fluid and filter on the trans with fresh Dex6. It has ~1000 miles on it, still pink and smells ok.

I've reset the adaptive values a few times, with no change.

Which reminds me of another problem that's developed. Every time I get in it after sitting more than a day or two it has a high idle (~1200rpm) that is only brought down when I reset the adaptive values.

 

How many miles on the Disco? Have you cleaned the IACV's pintle and port of carbon? That can help. The ECU counts rotations of the pin in and out. I don't know about the synthetic blend trans fluid even though it says it's backwards compatible, Dexron IID was the recommended fluid in the manual. IV would be as high as I'd go. I've had a few transmissions that failed after fluid/filter replacement. I generally leave them alone when over 100k unless the PO was on top of it from the start. Purge valves are a commodity item, the fuel tank pressure sensor would be a whole unit replacement unless it's a corrosion issue with the connectors. Wire brush and dielectric grease those.

 

Governor seals.

 

I changed the fluid and filter at 164k. It wasn't as bad as I've seen, but it wasn't great. Today I took it on a ~120 mile round trip and the transmission performed flawlessly. I'll still think I'm gonna run some cheap no name ATF through it a few times, and then fill it up with some Dex3 (if I can find it) or Max Life with a bottle of Lucas.

I have not clean the IAC yet. I'll give that a shot before I go buying parts. It idles perfectly every time I reset the adaptive values though, which is throwing me off. It's like the ECU is losing the position of the IAC. We'll see what cleaning does.

Don't say that.

 

I had much trouble resetting the idle speed and having the ECU keep it as well. It's a crap-shoot. If you buy another Idle Air Control Valve look in my signature for the two vendors I recommend, also Rovers North I hear is not so bad these days. OEM Rover IACV is $462 bucks, up to you.....

One of the biggest reasons I gave up on Rover after beating my head against a wall for 8 years is software control over the ECU. The original setup was Testbook T4, it counted the steps and you can control it's final idle speed by hard setting the steps. It's going to idle high when cold until warm, ECU has one temp sensor specifically for itself, the other tells the dash gauge your overheating...... If your still having an issue with the IACV setting try replacing the ECU's coolant temp sensor. It will either fail high or low and in either case it messes up the ECU settings.

 

For $462 I can reset the adaptives every day, haha. I've found them all over the board though. Rock Auto has some $18 options.

Do they require a special learn procedure? I've read of people pulling them along with ECUs at the junkyard while chasing similar issues.

 

Don't buy a parts palace part, get one from one of the Vendors I listed, your going to be much happier because they work. Yes pull as many parts as you can hide from a junk yard..... if they even have a Rover. I always took a electricians tool bag out with me..... all the smalls I could stuff in it. I still do that....... You'll want to match the same length of the old one with the new one, they screw in/out, just get it as close as you can. Sorry, that is also how I cured my idle speed, I played with the length by adjusting it in and out, started the motor to see where it would land and then doing a reset to save it.

 

Jeep 4.0 IAC = same as 96-99 D1, trans wise make sure your kick down cable is adjusted properly or it could act weird shifting. You must have the IAC tip & hole clean or it will never be very happy. How are u resetting the adaptive settings?

 

Best, what does your buddy have for reading GEMS ECU? You mentioned it in another post awhile back, one of your trucks.

 

My IACV died and a unit from Napa has performed flawlessly for the past four years. YMMV. I bought the new IACV from Napa (PART # :CRB 21856), pulled the pintle out as far as the old unit was, installed new and everything is back to normal. No re-flash needed. Lucky...for once.

I'd also check the health of your battery & alternator. When my battery is drained by for example, leaving the lights on, after a jump start the idle is very high until the battery is charged. After that, it behaves as normal after the next start up. Again, YMMV.