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Old 03-22-2018, 04:19 PM
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Tugela Tugela is offline
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I recently replaced plugs (Champion copper), wires (Kingsbourne), ignition coil (Pertronix) and distributor (Pertronix) on my 1993 RRC. Had a pro Rover tech set the timing. Checked connections on all new wires.

Issue: when I release the throttle, the engine stumbles a little as the revs wind down. Once at idle the engine settles down and smooths out. Under load the engine sounds great. It's just the transition between load and idle where it runs rough.

I'd appreciate any suggestions on what might be causing this. Symptoms were not present before installing the new distributor, so I'm guessing the issue lies in that direction.
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Old 03-22-2018, 06:34 PM
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And bet it is very annoying considering all that you have done on it.

Wish I could help - good luck and look forward to hearing the fix.
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Old 03-22-2018, 08:30 PM
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Quote:
Originally Posted by Tugela View Post
I recently replaced plugs (Champion copper), wires (Kingsbourne), ignition coil (Pertronix) and distributor (Pertronix) on my 1993 RRC. Had a pro Rover tech set the timing. Checked connections on all new wires.

Issue: when I release the throttle, the engine stumbles a little as the revs wind down. Once at idle the engine settles down and smooths out. Under load the engine sounds great. It's just the transition between load and idle where it runs rough.

I'd appreciate any suggestions on what might be causing this. Symptoms were not present before installing the new distributor, so I'm guessing the issue lies in that direction.
Sounds like your minimum idle isn't set right.
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Old 03-22-2018, 08:57 PM
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Any tips on how to solve that?
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Old 03-22-2018, 09:18 PM
discostew discostew is offline
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You have a rubber hose coming around the back of the plenum. It is the air tube for most of what enters the engine thru the IAC. If you pinch that off the truck should still idle. So if you have that pinched off and the thing idles like shit, turn the idle air bleed with a allen head. I think it's a 3/16th. So you will be letting more air into the throttle that the IAC doesn't control.
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Old 03-22-2018, 11:44 PM
XCELLER8 XCELLER8 is offline
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Originally Posted by discostew View Post
You have a rubber hose coming around the back of the plenum. It is the air tube for most of what enters the engine thru the IAC. If you pinch that off the truck should still idle. So if you have that pinched off and the thing idles like shit, turn the idle air bleed with a allen head. I think it's a 3/16th. So you will be letting more air into the throttle that the IAC doesn't control.
sorry to hi-jack....but if you have one of these 3.9's....and it's idling slightly high 850-900 rpm ( code 48), and all else seems fine, no vac leaks, throttle body spotless,etc....can you use this same method to turn the base idle down ??
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Old 03-22-2018, 11:56 PM
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Quote:
Originally Posted by discostew View Post
You have a rubber hose coming around the back of the plenum. It is the air tube for most of what enters the engine thru the IAC. If you pinch that off the truck should still idle. So if you have that pinched off and the thing idles like shit, turn the idle air bleed with a allen head. I think it's a 3/16th. So you will be letting more air into the throttle that the IAC doesn't control.
Thanks, I'll check that out. Just drove the truck tonight and noticed at a stop the engine was idling at about 400 rpm.
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Old 03-25-2018, 09:35 AM
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Start with cleaning the stepper (IACV). Then there is a list of other things before adjusting base idle.
What is your timing set at... 6? btdc?

Couldn't find the list of other things to check before setting base idle (will keep looking) but here's a good write up on setting BI.
http://c7743.r43.cf2.rackcdn.com/Dow...le-air-gap.pdf
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Old 03-25-2018, 11:08 AM
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Thanks for the link, I'll check that out.
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Old 03-27-2018, 12:50 PM
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Quote:
Originally Posted by Tugela View Post
Thanks, I'll check that out. Just drove the truck tonight and noticed at a stop the engine was idling at about 400 rpm.
If you turn the a/c on (which should raise the idle rpm), does it still do it?
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Old 03-27-2018, 04:32 PM
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Quote:
but here's a good write up on setting BI
that is really great information!

many thanks for sharing.
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  #12  
Old 04-22-2018, 09:13 PM
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Not sure if this is the ultimate solution, but the problem of the engine surging at low RPM with no throttle seems to be resolved. I tightened the throttle cable tensioner a little bit. This is the black plastic knurled knob that adjusts the throttle cable near the plate. Now if I lift off the accelerator the surge is gone. Press on the brake and same thing - no surge. There may yet be another issue that this simple fix has masked, or maybe it was just a simple fix. Time will tell.
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Old 04-23-2018, 05:52 PM
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Mine was loose as well when looking around awhile ago. Idle wasn?t being effected yet thought maybe full throttle was so tightened it to take the slack out. Didn?t notice much difference as can?t remember the last full pedal to the metal acceleration in the Rangie.
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Old 04-23-2018, 10:03 PM
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The plot thickens. I was poking around this evening and noticed two things:

1. The hose leading from the throttle towards the back driver's side of the engine bay was cracked
2. That hose led to a white plastic barbed T-junction. The other hose that connects to the T had broken off the junction and was just hanging there, also cracked. I followed that hose towards the front of the engine bay and the other end was hanging in space behind the driver's headlight.

Looks like I have some hoses to replace. Am I correct that this is part of the cruise control system? In which case that wouldn't affect the idling issue. The hose from the throttle to the T-junction is obvious. Question: for the other hose leading forward off that T-junction, what does the other end connect to? I didn't see an obvious place for it in the front of the engine bay.

I wouldn't use the cruise control even if it worked, but replacing some vacuum hoses is so cheap and easy why not do it?
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Old 04-24-2018, 11:28 AM
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Can you post some pics of the hoses?
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Old 04-24-2018, 11:36 AM
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they sound like the hoses for cruise control
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Old 04-24-2018, 01:45 PM
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There should be a round black bulb under the air intake or in that general area. It's the vacuum bulb for the cruise. If your cruise doesn't work (like mine), you can cap it off. Check where the other part of the Tee goes first.
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Old 04-24-2018, 10:39 PM
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I got around to adjusting the base idle as described in the Rovers North instructions in post #8. I only took a short test drive, but the performance felt improved and the engine speed transitions under braking and coasting were smooth. The surging appears to be gone. More miles will reveal how things have settled out, but for now it seems better.
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Old 04-26-2018, 08:45 AM
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Great to hear it is running better for you. Knock on wood my base idle has never given my any issues.
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Old 04-30-2018, 01:01 AM
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Well, now it's doing the same surge again. Guess my adjustment of base idle did not address the issue. Will keep looking.
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Old 04-30-2018, 11:17 AM
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I don't know if base idle adjustment is ever warranted on these trucks. A PO of my latest LWB dicked with it, and it occasionally hot-starts with 1500 rpm idle.
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Old 04-30-2018, 11:45 AM
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Ive had to adjust base idle when changing displacement, but that shouldnt be a surprise
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Old 04-30-2018, 12:14 PM
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Ive had to adjust base idle when changing displacement, but that shouldnt be a surprise
I am surprised that IAC did not account for that. It could be closer to the end of its travel range.
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Old 04-30-2018, 02:09 PM
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It tried. 3.9 plenum on a 3.5 idled over 1000

3.9 plenum on a 4.6 was close, but still a little high
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  #25  
Old 05-01-2018, 12:20 PM
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What are the chances that the problem could be caused by a faulty ignition amplifier? I read some past threads in this forum and found similar problems with that as the solution. Then I realized that my new distributor didn't come with a new ignition amplifier, so I reused the old one. Which could be the original from 1993 as far as I know. Atlantic British wants $72 for a new ignition amplifier, which is a little more than I want to spend on a guess.
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