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Someone asked me about what I did about that issue. Please use this link you will need to scroll a good bit down

 

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1998 Lamborghini Diablo SV
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Timely post @Sudesh. Just installed a missing Carter motor on my 98 SV. Would you mind commenting on my post regarding the initial rev surge? Based on your thread, sounds like it's normal.

Discussion starts around post #91 after I installed the motor.
 

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Not a problem commenting, however I think if your car is 1998? then it's different, some of the other gentlemen please jump in & coments......
 

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1998 I think will have the Carter Motor which sets revs to approximately 2000 on cold start and keeps it there for a minute or so until slowly dropping back to idle. It'll also activate on hot start but should immediately pull back to allow engine idle.
 

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1998 Lamborghini Diablo SV
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1998 I think will have the Carter Motor which sets revs to approximately 2000 on cold start and keeps it there for a minute or so until slowly dropping back to idle. It'll also activate on hot start but should immediately pull back to allow engine idle.
Yes, my car has a Carter motor. That's pretty much exactly what occurs. May I ask how you know this? Is there a reference? Thanks!
 

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1998 Lamborghini Diablo SV
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By spending many an hour in the garage trying to fathom how it should work!


There's a bit more to it though as I found I had to adjust the TPS to get it working properly to prevent it retracting back too quick and creating a L Bank CEL.

Still does it now on the hot start if I don't catch it right.
I've read that Lamboweb article about a dozen times. If you've read any of the earlier posts in this thread, you may know that I suspected a bad Carter motor. Took off the engine cover and turns out I didn't have a motor (or the bracket) at all. The plug going through the firewall to the Carter ECU was just sitting there with nothing attached to it. I was finally able to source a motor and bracket and just installed it. Everything seems to be working as you described. RPM surge to about 2000 on dead cold start, settles down to a tick above 1100.
I've had an intermittent L bank CEL ever since I got the car and it's still there even after installing the Carter. I assume that's more due to the fact that I have Quicksilver headers, though.

My question was how do you know that the surge to 2000 RPM's on cold start is 'correct'?
 

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I don't but the owners manual states 'It may exceed 1500rpm for the first few minute'. I think its all set by where the Carter Motor holds it. You can set the offset distance from the motor to the throttle linkage, but I think the ECU decides how far the motor should extend depending on parameters

One thing that throws my L CEL is sometimes when I hot start. If I turn on the ignition key and don't start it immediately, the carter retracts and then it throws the code. However, until I settled to where I am at the moment, I was getting the CEL all the time

Do you get the 3 cycles from the carter motor when you shut the engine off?
 

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1998 Lamborghini Diablo SV
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I don't but the owners manual states 'It may exceed 1500rpm for the first few minute'. I think its all set by where the Carter Motor holds it. You can set the offset distance from the motor to the throttle linkage, but I think the ECU decides how far the motor should extend depending on parameters

One thing that throws my L CEL is sometimes when I hot start. If I turn on the ignition key and don't start it immediately, the carter retracts and then it throws the code. However, until I settled to where I am at the moment, I was getting the CEL all the time

Do you get the 3 cycles from the carter motor when you shut the engine off?
I only have the owner's manual for an early Diablo which didn't use Carter motors. Would love to see/get a later SV version. If it does indeed say that, that would be comforting.

I've read about the 3 cycles after shutting down, but I don't hear anything. I've read that's it's fairly loud and would be hard to miss. What would it mean if it's not cycling?
 

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You can't miss it as the throttle linkage moves with it.

If its not doing it, that would give you a CEL. The only way I got this set was by adjusting the TPS, very much trial and error though!

I think it can be set on a LRAS but nearest one to me is 4 hours away
 

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1998 Lamborghini Diablo SV
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You can't miss it as the throttle linkage moves with it.

If its not doing it, that would give you a CEL. The only way I got this set was by adjusting the TPS, very much trial and error though!

I think it can be set on a LRAS but nearest one to me is 4 hours away
What's the purpose/importance of the cycling after shutdown? The Carter seems to be doing its job otherwise. Fuddling with the TPS to get rid of an intermittent L bank CEL seems silly.
 

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Discussion Starter · #13 ·
Hard to beat a real Lamborghini Diablo before Audi stepped in lol.
 

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MAP sensors were the cause of a lot of my CEL issues - replaced all 3 and none since.
Warning you may lose some skin fitting the one near the radiator expansion tank - it was never designed to be replaced easily, unfortunately.
The MAP sensor is Marelli PRT03/04 used in a lot of European cars of that era. Around £40 each. Equivalents are also available.
 

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Discussion Starter · #17 ·
I know, seems like even if I pull a funny face at the car it
I know, seems like even if I pull a funny face at the car it throws me a CEL!
Very good lol that's were the original Diablos, you could go to most places, & do a diy job from pieces found there even a garden hose lol
 

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This is a great thread, thank you everyone. Someone mentioned CEL lights which are mostly standard on Diablos! Kidding aside, Davo mentioned MAP sensors. That’s the last thing I have yet to do in my car which still occasionally throws CEL’s. It must be my remaining issue. Again, I have no Carter motor on my car but it also runs high on cold start at 2000-2500 RPMs for a good three or so minutes before settling down to 1050 RPMs. I would not doubt at all if your Carter motor system is set to this same level.
 
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