 | Home > V8 > 3.9l V8 serpentine engine failing emissions |
 
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| falkster Member Since: 12 Nov 2023 Location: Sutton Coldfield Posts: 64   
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Hi, I am in the process of buying a 1988 Land Rover 110 that had an engine swap from its original 3.5l V8 to a serpentine belt 3.9l V8.
The guy selling it kindly offered to renew the MoT before handing over the vehicle. Now it appears to fail the emissions test on the original test due to an unstable idle speed and on the re-test with corrected idle, it failed again... I am sitting remotely on this so can't look at the vehicle, but the question I have, is this a common thing? and if anyone else had similar issues, how did you solve it? Is the only way to have a tester who happily raises the idle speed slightly to get results?? I am keen to get the vehicle rather sooner than later, so just trying to figure if I can siomehow draw from the collective knowledge. Thanks for your help.  |
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2nd Jun 2024 8:42am |
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| sasdiscos Member Since: 22 Jul 2023 Location: UK Posts: 151 
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As mentioned stepper motor. Don’t buy cheap.
Also, lambda sensors worth a check. Mine just failed and I needed a new lambda. I’m going to assume that the Brit part lambda sensors will be a yearly service item going forward. Lucas ones no longer available. Steve. |
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2nd Jun 2024 4:26pm |
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| Linds Hanson Member Since: 16 Jan 2021 Location: Cornwall Posts: 485 
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Probably worth disconnecting the stepper motor and setting the idle with the air screw for the MOT.
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3rd Jun 2024 5:23pm |
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| sasdiscos Member Since: 22 Jul 2023 Location: UK Posts: 151
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If you’re going to play around with the idle adjuster screw make sure you follow the lr technical booklet. They are set from the factory and should never need adjusting.
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3rd Jun 2024 9:32pm |
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| TexasRover Member Since: 24 Nov 2022 Location: Paris Posts: 1043  
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1988, did they have injection then? 3.5 came in carb version at least in 1984 (I had one). And swapping the block to a 3.9 should make no difference to the applicable emission requirements if 1988, which is not much of a requirement. Injection, cat etc was only introduced in Europe as a requirement to meeting emissions in 1992. Sounds like the Carbs need a tune up, check ignition etc. Old school, its easy plenty of U-tube to guide you. |
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4th Jun 2024 6:33am |
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| Lodelaner Member Since: 04 Feb 2010 Location: Lambourn Posts: 631 
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On my 3.9 serp an LR 'specialist' started replacing things and messing with the idle speed. It still was over on emissions. They had it for 3 months, wanted £1k (didn't pay that much, but it's another story) and didn't fix it. V8s are prone to vacuum leaks - which messes with idle and rich fuelling. So with the gift of lock-down time I chased every vacuum line and hose. Many were iffy, and replaced to ensure reliability, but didn't fix the issue. Turns out mine was letting in air through the inlet manifold valley gasket because the manifold wasn't tight. The lambda sensors were seeing lean mixture and enriching it. The mixture was fluctuating, causing hunting and fast idle because if the excess, non-metered air. The symptoms you describe are similar. So I would suggest you have any vacuum leak checked methodically and eliminate that before starting to change parts. The sensors are pretty simple on the 14CUX and failed ones seem to be fairly rare. Also check the dizzy cap - even OEM Lucas versions are rubbish these days, and can rotate on the distributor body causing all sorts of intermittent timing and ignition symptoms. It has taken 2 years and about 10 attempts to get the base idle and mixture correct again. So mess around with it at your peril! JB @Lodelaner Instagram Youtube greenlaning and other LR related content |
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5th Jun 2024 10:05am |
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| falkster Member Since: 12 Nov 2023 Location: Sutton Coldfield Posts: 64
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Thanks everyone for your valued input. Lambda sensor it was!
The vehicle now has passed the MoT and I'll pick it up in the coming days. Time to start a new "My Defender" thread. Again, thanks all! great forum...  |
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6th Jun 2024 1:52pm |
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| falkster Member Since: 12 Nov 2023 Location: Sutton Coldfield Posts: 64
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What a story! still using the V8 or did you have enough after that? Might contact you on the fault finding route. I'm new to V8's and even though it seems to work now, I might give the vacuum hoses checking a go. Did you have diagram or anything that guided you where and what exactly to check? |
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6th Jun 2024 1:59pm |
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| Lodelaner Member Since: 04 Feb 2010 Location: Lambourn Posts: 631
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Still have it - it's my forever Ninety!
My first car was a RRC 35 years ago and I'm still learning about them. There are many vacuum hoses plugs and blanks on the manifold - so I simply checked each hose in turn by removing, squeezing to check for splits and cracks and refitted. Glad you got it sorted - and thanks for sharing the solution! JB @Lodelaner Instagram Youtube greenlaning and other LR related content |
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6th Jun 2024 2:09pm |
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