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Bosch K-Jetronic CIS tuning, 86HC, 87HC, 88 X180 Esprit - Page 3 - Engine/Ancilliaries - The Lotus Forums Jump to content

Bosch K-Jetronic CIS tuning, 86HC, 87HC, 88 X180 Esprit

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I've got a 1988 Esprit SE (By Vin, 4 Cyl) and I'm currently troubleshooting the low cold idle (< 900rpm), high idle when warm, a bit gutless before boost problem.  Originally the idle would simply fail without a light throttle, any more or less throttle would cause stall.  I suspected my Auxiliary Air Valve was the issue.  I adjusted its open position to the max by the peg / nut on the front which made cold starting a bit easier but added hot high idle (about 1300rpm) and worse power issues.


 Here's what I know about the AAV I have and my current symptoms:


0) the CIS Auxiliary Air Valve in my car is a Bosch 0 280 140 143, not the 0 140 140 143 listed in the original Post.  Is the original post a typo?  

1) when cold (20deg C), AAV is barely open 2-3 mm

2) the valve can easily be opened with a thin wire coat hanger, requiring very little force; no visible gunk or soot.

3) the valve inside is still noticeably under spring tension

4) the adjustment peg (under the nut) is open as far as it can go (moving it in the other direction closes the opening)

5) the 12V connect give 40Ohm resistance

6) when cold (20deg C) the car idles rough, threatening to stall, very lightly giving gas to 1000 rpm barely stables the idle. Also misses and backfires.  Exhaust smells rich.

7) when warm, idles slightly above 1000 rpm

8) when hot, idles above 1300 rpm

9) car feels gutless on start when cold, nearly stalling

10) car feels gutless in motion when hot before boost, and even then.

11) completely bypassing the AAV (connecting In and Out tubes together) on cold resolves all cold start issues:  smooth idle near 1000 rpm, no backfiring, no missing, no fuel smell in exhaust.


All of this leads me to the following conclusion: the bimetallic strip is twisted or bent or otherwise busted and even if it is getting heated, it is not moving.  As I can't easily get in to the AAV without a saw, I don't think I can check.  I'm sure enough that I'd like to replace it if no-one has a reasonable idea on how to fix it.


However,  I'm having difficulty finding a source for a 0140140143 suggested in the Original Post and very few for the 0280140143 I find in my car.  Has any one successfully replaced the AAV with any other Bosh AAV of similar shape form factor and design such as 0280140122, 0280140155, 64410?


I'm pretty new to this so any guidance might help.

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The correct PN is Bosch 0 280 140 143.

Check Lotus Service Notes, section LF. There is a procedure for testing AAV. Check it for tiny holes drilled by PO to pass SMOG test, happens pretty often.

How this condition evolved? Sudenly or gradually? Did you buy your car with condition like that?

How long do you own the car, and how long the above symptoms exist?

When did you flush the tanks last time?

Do you have access to the Gunson Gas Tester?

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Thanks for the quick reply John!


I'll go through the correct steps listed for the AAV test tomorrow morning.  I didn't see any holes in the body of the AAV when I had it off this afternoon.


I bought the car in June, passed 3rd party purchase inspection, had it shipped from LA, it failed Canadian safety inspection due to brake rotor warping and a cracked indicator.  Took until September to get it on the road and I noticed the problems immediately.


The PO warned of some lack of power when hot but none starting.  However, LA summer is a lot warmer than Vancouver BC fall ;).  No substantial high idle problems existed before I opened the AAV more using the adjustment nut. 


The tanks were flushed when I had the fuel pumps and lines replaced in July.


I don't currently have access to a Gunson Gas Tester.  Currently, my mechanics tool chest consists of a ratchet / driver set, a flashlight, and a digital multimeter ;).  Jackstands and torque wrench are being purchased next month.


BTW: is it safe to stand on any part of the trunk? getting a reasonable view of what I'm doing this far forward in the engine is a challenge from the side as I'm pretty small.

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I found the Airtex / Wells part number for the Auxiliary Air Valve (Bosch 0 280 140 143) as the 1986 Audi 5000 Idle Air Control Valve 2H1023.  Their pic even shows the Bosch part number :)


Also, found this potentially useful resource for cross matching similar Bosch parts, as long as you can make your way through the german. You'll need to register but it is free


Don't quote me on it, but I think it says that the 0 280 140 144 is the same as the 143 but was done OEM and marked as Audi not Bosch.

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Thanks for the vehicle history.


As it was suspected, there is a "PO factor" in this affair. You need to find out if he was a knowledgeable Lotus Enthusiast or just a car flipper.


Best you can do, is to call the PO and ask him to honestly tell you what problems did he have and how he "took care" of them. Detailed confession is worth a lot, at least ½ of your problem solution.


You may state, that you will not hold him responsible or seek transaction annulment.


When it comes to PO statements - apply “trust but verify” MO, always!


Yes, you can use Audi or VW AVV as long as they have similar opening times.


Rear boot floor is fragile, do not step inside. Either, build a "gurney", or put a thick piece of  plywood at the bottom to distribute your weight. Also, be careful not to apply weight over the spoiler, it may crack.


If you don't have Gunson, read you plugs, instead.

Edited by MrDangerUS

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