Hello Gents and Ladies, I have a 2004 Disco 2 that's reving on its own on a cold start (only sometimes as well but definitely 50% of the time). Codes are all cylinders misfiring and engine Drivers side engine bank running lean.

Here is a video that I just managed to catch the other day as it happened. It will do this for 10 or so seconds. Sometimes much more exaggerated and sometimes fairly minor like this time shown in the video.

https://www.dropbox.com/s/u5veoheghr...20REV.mp4?dl=0

I've been chasing down a few of the cylinders misfiring for a little while and I appeared to fix it by replacing all the air leaking injectors. Ran wonderful until the other day just randomly one morning, now we have this.

Any help would be appreciated. Here is a list of the new parts I've installed over the past year or so.

Upstream O2 sensors
Fuel Injectors
Plugs and Wires
MAF sensor
Throttle Position Sensor
Upper and Lower Intake gaskets
Valve cover gaskets

Thanks!

 

Have you cleaned out the IAC valve?

 

I have not. I can do that today though. Is it straight forward or is there something I should know or whatch for?

Thank you!

 

Plenty of threads on here about cleaning it out. Basically remove it and hose out the inside with carb cleaner.

 

Awesome, I will look it up and give it a shot. Thank you.

 

So I unhooked the hoses and cleaned it. Fired up the truck to see if it was actually working, it is. It's clean now but no difference in the low rough idle, or misfires. It still revs sometimes as well. I do think I have found a small air leak in the Valley Gasket right below the fuel injectors. Or perhaps it could also be the fuel injectors.

I also went over to the pick and pull and grabbed the IAC valve off that one, cleaned it and installed it. No change, but now I have two!

Any Ideas?

 

The lean codes certainly indicate a vacuum
leak someplace but the erratic high idle is a little confusing. Sounds like you have eliminated the IAC. I think you next step is to perform a smoke test looking for a leak. Do you have an ODB diag tool? Is your drivers side pre cat O2 cycling as it should?

 

Don't know if this applys to D2s, but D1s rev high when they need the adaptive values reset.

 

SOLVED

Thanks for all the help everyone! I appreciate it, thought I would write a quick update on the issue. So I sprayed around the running engine to see if I could locate an air leak anywhere, sure enough it's leaking somewhere around the Plenum/lower valley gasket. Buuuut I just replaced all those in June along with all new refurbished Fuel Injectors and new O2 sensors. So I decided that I would try again thinking I must have messed up something. It ran great for about 6 weeks until the O2 sensor stopped working, engine started to rough idle, cylinder misfires and once it got cold out the truck started to do the revving on it's own during start up, I even had a few instances of coming out of a store after about 20 minutes inside and the truck would start but die in about 10 seconds. So I was just at a loss because it was only sometimes. Then when the truck started from cold, it would run great after it's initial revving but would slowly degrade as the engine warmed up.

So I decided I would just try again over the Christmas break, eggnog, rum, and engines! I ordered all new gaskets, O2 sensor and I did the wires and ignition coils just because I thought it's at 160k and I'm going to have them off, might as well.

I took the whole top off down to the Valve covers and Lower Valley Gasket. When I took off the Fuel rail all 8 injectors just popped out without any problem, so that caught my attention immediately. I unclipped them from the rail and had a closer look, it appeared as though all of the new o-rings that came on the refurbished injectors had shrunk, I could actually move the injectors in and out of the plenum without any resistance whatsoever. So this was my culprit. All 8 were obviously leaking huge amounts of air causing the engine to struggle hard, as it's misfiring and running lean. Luckily I had a head gasket rebuild kit that included 16 injector o-rings that I randomly bought from RockAuto a few years back on some blowout sale. haha So I redid all the o-rings and when placing the injectors back in there was resistance and a perfect tight fit. I replaced all the gaskets anyway because I had them, coil packs, and wires. Fired up the truck and smooth sailing. So perhaps the o-rings that came on the refurbished injectors were not made for use with fuel, or high temperatures as they had shrunk considerably. Only time will tell if these new ones I've installed do the same thing or not.

Hopefully this helps someone having a similar problem.

Engine codes were.

P1174
P1171
P0130 - O2 sensor
Then I had each cylinder misfire and random cylinder misfire codes which is 9 different codes.
Engine lean bank 1 and 2.

Now, I have zero! Knock on wood or an engine or whatever...

 

I had a friend working on an 07 RR and he ordered new fuel injector O-Rings, and pretty much the same thing happened they were totally the wrong size. Ended up using some O-Rings of a dead pair of injectors he had laying around and they worked no problem. Funny thing was he ordered the O-Rings directly thru the LR Parts Department. He's taking them back for a refund no doubt. Glad you got it fixed!