Fault code 48 after installing new IACV - Defender Source
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  #1  
Old October 4th, 2015, 05:36 PM
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Fault code 48 after installing new IACV

I notice my idle would surge and stick high often and removed my IACV/Stepper motor and ended up replacing it with a new one. After replacing yesterday it ran great. Today after running it for a while I noticed the idle was right at 1000 rpm (as opposed to just below it) and then the check engine light came on.

It is returning code 48 which I understand to be : STEPPER MOTOR
Check base idle speed - see setting procedure. Refer to tests 15 and 16 of continuity test procedure. Check road speed sensor - refer to test 25 of the continuity test procedure.

Before messing with the base idle should I be sure it isn't something else? The new Stepper motor is a genuine land rover part. Is it normal that base idle should be set after installing a new Stepper motor?

And then the question of how do I adjust the base idle? Where is the adjustment ?

Thanks guys I'm sure I can handle the adjustment just don't know where it is or if there is something else I should check first.

Will
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  #2  
Old October 4th, 2015, 06:45 PM
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If the base idle has not been messed with it's unlikely to need adjustment. Check for air leaks. The AICV is the stepper motor.

I would also check the timing and the throttle cable tightness. The code is being thrown as the ECU can't lower the idle to the target ... which is about 550 rpm from memory.
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  #3  
Old October 5th, 2015, 09:12 AM
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Did you clean the intake manifold where the stepper goes in?
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  #4  
Old October 5th, 2015, 10:39 AM
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The AICV might also not be working--I would remove it, leave it plugged in, and cycle the ignition on and off--the plunger should go out and in. I would start with that and make sure it operates before changing anything else.
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Old October 5th, 2015, 12:47 PM
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Originally Posted by Davis View Post
The AICV might also not be working--I would remove it, leave it plugged in, and cycle the ignition on and off--the plunger should go out and in. I would start with that and make sure it operates before changing anything else.
^this

Best suggestion!
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Old May 3rd, 2016, 07:43 PM
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I am trying to sort an idle issue with my 95 RRC. Idle was running high in park when I first acquired it (1100-1200) in park. Never had any stalling issues, drives fine. Actually has better idle when in drive sitting. Replaced AICV and the idle seems about the same. Adjusted the hex screw some to bring idle down to about 800 rpm when in park. Kinda stays there, but it's not clean. When moved to drive it goes down to about 500 or so rpm. Still notice rough idle.
Is this as good as it gets? Or is there something else to check? Throwing 48 code even after cleared out.
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Old May 4th, 2016, 02:41 AM
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Quote:
Originally Posted by WeBeCinYa View Post
I am trying to sort an idle issue with my 95 RRC. Idle was running high in park when I first acquired it (1100-1200) in park. Never had any stalling issues, drives fine. Actually has better idle when in drive sitting. Replaced AICV and the idle seems about the same. Adjusted the hex screw some to bring idle down to about 800 rpm when in park. Kinda stays there, but it's not clean. When moved to drive it goes down to about 500 or so rpm. Still notice rough idle. Is this as good as it gets? Or is there something else to check? Throwing 48 code even after cleared out.
Did you set the timing before messing with the hex screw?

The base idle is factory set and you should make sure everything else is spot on before changing it.

If someone set the idle with the vacuum advance connected it causes all sorts of weird idle issues.
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  #8  
Old May 4th, 2016, 07:29 AM
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Originally Posted by leastonce View Post
Did you set the timing before messing with the hex screw? The base idle is factory set and you should make sure everything else is spot on before changing it. If someone set the idle with the vacuum advance connected it causes all sorts of weird idle issues.
I did not touch the timing. I assume I should start square one with setting timing, then setting base idle per the rave manual? Then looking for other issues like vacuum leaks, ect?
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Old May 4th, 2016, 07:42 AM
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Originally Posted by WeBeCinYa View Post
I did not touch the timing. I assume I should start square one with setting timing, then setting base idle per the rave manual? Then looking for other issues like vacuum leaks, ect?
Timing and vacumn leaks are a great place to start. If there is a leak in the vacuum advance it can impact the timing.

When I got my truck years ago it had been timed with the vacuum advance connected. It wouldn't idle properly. It was always too high. When I timed it it ran so much better.
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  #10  
Old May 4th, 2016, 07:47 AM
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Quote:
Originally Posted by leastonce View Post
Timing and vacumn leaks are a great place to start. If there is a leak in the vacuum advance it can impact the timing. When I got my truck years ago it had been timed with the vacuum advance connected. It wouldn't idle properly. It was always too high. When I timed it it ran so much better.
TPS is also something I've heard could be the issue...any easy way to rule that out?
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  #11  
Old May 4th, 2016, 08:49 AM
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Matt, quit farting around. Replace the vacuum advance hose with some 1/8 ID silicone hose from McMaster. Also buy 1 foot of black silicone 1/4 ID hose. Replace all the short segments of hose that connect the vacuum lines from the cruise control and charcoal canister. Check the bypass air hose on the back of the plenum for cracks. check the hose from the breather to the T piece for cracks. Clean out the T piece. Check the flexible hose that is on the mass air sensor for leaks or cracks. Also, I like to put "Right Stuff" in the joint between the upper and lower intake plenum air box, just for my own edification.
I bet if you do all that you will see your idle settle down to where it is supposed to be. Generally, vacuum leaks will cause a rough or low idle (fuel starvation form a lean mixture). High idle would lead me to think there's a timing adjustment needed.
If your TPS was faulty you'd have a very hard time driving the thing.
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  #12  
Old May 4th, 2016, 09:51 PM
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Originally Posted by o2batsea View Post
Matt, quit farting around. Replace the vacuum advance hose with some 1/8 ID silicone hose from McMaster. Also buy 1 foot of black silicone 1/4 ID hose. Replace all the short segments of hose that connect the vacuum lines from the cruise control and charcoal canister. Check the bypass air hose on the back of the plenum for cracks. check the hose from the breather to the T piece for cracks. Clean out the T piece. Check the flexible hose that is on the mass air sensor for leaks or cracks. Also, I like to put "Right Stuff" in the joint between the upper and lower intake plenum air box, just for my own edification. I bet if you do all that you will see your idle settle down to where it is supposed to be. Generally, vacuum leaks will cause a rough or low idle (fuel starvation form a lean mixture). High idle would lead me to think there's a timing adjustment needed. If your TPS was faulty you'd have a very hard time driving the thing.
Ordering hoses Bill. Do you know the diameter of the hoses from vacuum lines and cruise/charcoal canister? What type of hose material is suitable for that?
Thanks for the tips. Going to go through each and replace until something changes.
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Old May 4th, 2016, 10:49 PM
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The vacuum lines (nylon lines) are 1/4 OD. Get 1/4 ID silicone hose.
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  #14  
Old May 11th, 2016, 05:28 PM
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Still having idle issues on the RRC... Ordered some new hoses, replaced, no obvious changes. Replaced AICV with different one, no obvious changes. Cleaned out T connector, it was dirty, no obvious changes. Checked for any other loose hose connections, nothing noted. Tried to reset the base idle per the procedure link below. One thing I noticed, when I unplugged the AICV per step #11, the idle shot up to 2000 rpm, and step #12 didn't work out, even if I adjusted the hex screw all the way down (closed) it was still roaring at high rpm. According to the instructions, I should have been able to dial it down to <650 with the AICV unplugged. That wasn't happening.

Base Idle Setting Procedure | Range Rover Classic Maintenance

With the AICV plugged in, I can get it to idle ok around 750 rpm in Park, around 600 when in drive, but it still faintly searches and is not a clean idle, and worse when in park, better in drive.

Next suggestions...Fuel filter? Clean air idle valve? ECU issue? This has to be a simple fix, the engine runs beautifully otherwise. No interested in taking it in to shop for $120/hr guessing game... Any help appreciated!
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Old May 11th, 2016, 06:22 PM
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Maybe this is just as good as it gets per say, and my ocd will just have to live with it.

Check out the video below, sorry to bore anyone, but I recorded the idle starting in Park, then to Drive, then back to Park. At :38 seconds, :57 seconds, and then for a span of time towards the end of the clip you can see some faint searching.

The thing is, the needle moving doesn't bother me, its the vibration feeling it makes like its just not clean. The vibration or hesitation is noticeable mainly from the interior.

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Old May 11th, 2016, 06:53 PM
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I was hunting this same issue on my Defender. For what it's worth, there seem to be a few versions of the IACV floating around. I got two separate ones from AB (different part numbers), one from Rovers North and they all looked different from each other and from what was in the truck to begin with. Couldn't get any of them to make the the idle smooth. Finally got one from NAPA auto parts for like 20 bucks and the truck works fine. Naturally the ones from NAPA looked different than the ones from RN and AB. So long story short... swing by Napa and see if the one they have works better in your truck?
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Old May 11th, 2016, 07:00 PM
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Originally Posted by sflash868 View Post
I was hunting this same issue on my Defender. For what it's worth, there seem to be a few versions of the IACV floating around. I got two separate ones from AB (different part numbers), one from Rovers North and they all looked different from each other and from what was in the truck to begin with. Couldn't get any of them to make the the idle smooth. Finally got one from NAPA auto parts for like 20 bucks and the truck works fine. Naturally the ones from NAPA looked different than the ones from RN and AB. So long story short... swing by Napa and see if the one they have works better in your truck?
Know the NAPA part #? Or did you just ask for the Chevy Astro van one? Thanks for the tip!
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Old May 11th, 2016, 07:21 PM
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I actually got the part # of a thread in the forum and for the life of me I can't find it. I just searched my old posts and apparently it wasn't one of my threads. I'll keep looking when I get home..
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Old May 11th, 2016, 07:22 PM
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know the napa part #? Or did you just ask for the chevy astro van one? Thanks for the tip!
mpf21738
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Old May 11th, 2016, 08:02 PM
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Quote:
Originally Posted by sflash868 View Post
I was hunting this same issue on my Defender. For what it's worth, there seem to be a few versions of the IACV floating around. I got two separate ones from AB (different part numbers), one from Rovers North and they all looked different from each other and from what was in the truck to begin with. Couldn't get any of them to make the the idle smooth. Finally got one from NAPA auto parts for like 20 bucks and the truck works fine. Naturally the ones from NAPA looked different than the ones from RN and AB. So long story short... swing by Napa and see if the one they have works better in your truck?
Same thing here. Was getting code 48 and an erratic idle, replaced with a "genuine" one from AB, and the same issues persisted. Decided to go with the Checvy part, I think from Autozone, and it hasn't thrown the code since. It's been a couple of years.
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