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1998 Lamborghini Diablo SV
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Discussion Starter · #1 ·
This morning was my first opportunity to stretch the legs a bit after a hellish (or more accurately, frozen) week here in Texas. Was able to hit triple digits in 4th after I crossed the border into Mexico. Still haven't touched 5th gear.

The day wasn't without hiccup. Car is a 98 SV for reference. First off, car has intermittent starting issues. As it came off the delivery truck, it took 3-4 attempts to get the car started. It cranks, will attempt to idle and then die. Figured it was sitting in a cold truck for 4 days and thought little of it.
Now, this morning, it did the same thing. Starter will hum, the car will briefly start and search for idle then die. Some throttle application while it tries to stay running will eventually do the trick and the car will steadily idle at about 1100 RPM. On other occasions from a cold start, it'll turn over on the first crank.

After letting it warm up for a minute or two, pulling away from the driveway, the car almost immediately starts bucking with low RPM's in 1st gear. Not very graceful. Again, applying a bit of throttle will even it out a bit but will start bucking again as the RPM's drop. At highway speeds, the car seems to run fine.

Battery was just replaced, has been on a CTEK and reads as fully charged. No CEL's. New gas in the car 2 days ago. Starter rebuilt and new solenoid installed, new spark plugs, fuel filters by George Evans in mid-2017 but only about 3,000km ago.

Car was checked out by Veloce Motorsports in Kirkland about 6 months ago when it was noted "the vehicle has drivability problems and the engine isn't running smoothly" Screenshot of the diagnosis and fix below:

292844

So, temp probe replaced and exhaust leak addressed.

Being new to these cars, I fully expect there to be 'quirks' as part of the price of admission. What I don't want to happen is a seemingly innocuous quirk to become a bigger issue later, especially less than a week after getting the car.

Any advice?
 

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Sounds like the alternator
 

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1998 Lamborghini Diablo SV
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Discussion Starter · #3 ·
Sounds like the alternator
Possible. Car seems fine though once up and running for a bit. I'll have to find a multimeter.
 

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97.0 VT Roadster / 08 Gallardo Spyder
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A few suggestions:
1) call Josh at Veloce back and offered to pay him by the hour for some advice. He likely remembers your car and will give you pointers. Does the paperwork or does he recall that the car ran fine after that? If so, maybe one of his sensors has worked loose?
2) run two or three tanks through the car with seafoam cleaner, this will clean your injectors and at least on my car was a noticeable change.
3) easy enough to do, remove and inspect your air filters. Josh already cleaned the throttlebodies per his note above so the air filters are likely fine.
4) don’t mess with idle. It was already set and you noted that it hits about 1100 RPM when it runs properly. (1050-1150 is perfect)
5) I see the comment from another poster above to check your alternator. Not sure about that if your battery maintains a good charge between rides. if it does not, then certainly.
6) I recently replaced my coil packs because I had similar issues with occasional immediate RPM drop on starts and throwing my CEL‘s with “Random misfire”. And like you, I had new plugs, clean throttlebodies, new fuel and air filters, New belts and alternator running fine. Turns out when I removed the coil packs I found a ground wire on the coil pack assembly was not in the best shape. I cleaned the minor corrosion off and reassembled with the new coil packs and one of the two of those tricks did the job. No idle or CELs since.
7) plug in your OBDII reader to see if there are any codes throwing or stored. There is no guarantee that your CEL‘s on the dash are working properly so I would go plug an OBD in. Also, this will give you real-time diagnostics.
8) poke around all the vacuum hoses on the engine most particularly the passenger side. If your SV is like my VT, there is a vacuum hose and vacuum canister on passenger side that hoses can often work loose.
9) Beyond that, maybe air intake sensor or map sensor? Not 100% sure there.
10) another quirk on my car that I found that is easy enough for you to check is remove the two wiring harnesses from the two ECUs and examine the connector pins. On one of mine there was corrosion on one of the pins that took a toothbrush to clean. This, too, threw a code.
11) and finally, welcome to half the fun of owning a Diablo! 😎
 

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1998 Lamborghini Diablo SV
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Discussion Starter · #5 ·
Thanks.
My thoughts to your responses

A few suggestions:
1) call Josh at Veloce back and offered to pay him by the hour for some advice. He likely remembers your car and will give you pointers. Does the paperwork or does he recall that the car ran fine after that? If so, maybe one of his sensors has worked loose? I can try to give him a ring this week.
2) run two or three tanks through the car with seafoam cleaner, this will clean your injectors and at least on my car was a noticeable change. Was going to buy a few bottles of Techron and do this.
3) easy enough to do, remove and inspect your air filters. Josh already cleaned the throttlebodies per his note above so the air filters are likely fine. No mention of air filters being changed, but I would assume that bad filters would also manifest with hesitation under acceleration. Car seems fine under load.
4) don’t mess with idle. It was already set and you noted that it hits about 1100 RPM when it runs properly. (1050-1150 is perfect) Wouldn't even think of messing with it.
5) I see the comment from another poster above to check your alternator. Not sure about that if your battery maintains a good charge between rides. if it does not, then certainly. Battery appears to retain charge. CTEK doesn't give any indication the battery is discharged after a drive and goes to 'float' mode shortly after I park it and reconnect the tender.
6) I recently replaced my coil packs because I had similar issues with occasional immediate RPM drop on starts and throwing my CEL‘s with “Random misfire”. And like you, I had new plugs, clean throttlebodies, new fuel and air filters, New belts and alternator running fine. Turns out when I removed the coil packs I found a ground wire on the coil pack assembly was not in the best shape. I cleaned the minor corrosion off and reassembled with the new coil packs and one of the two of those tricks did the job. No idle or CELs since. I would assume if I had coil pack/spark issues, it would throw a CEL. There is a very small red 'R' in the bottom right corner of the bottom warning lamp strip that initially stays on but I'm fairly certain goes out soon thereafter. Checked the manual and have no idea what this light indicates, although my manual is for a first gen Diablo with the tall dash. Not sure if that makes a difference.
7) plug in your OBDII reader to see if there are any codes throwing or stored. There is no guarantee that your CEL‘s on the dash are working properly so I would go plug an OBD in. Also, this will give you real-time diagnostics. Just had the state inspection done 2 days ago and was told there were no codes on the OBDII scan.
8) poke around all the vacuum hoses on the engine most particularly the passenger side. If your SV is like my VT, there is a vacuum hose and vacuum canister on passenger side that hoses can often work loose. I'll take a gander
9) Beyond that, maybe air intake sensor or map sensor? Not 100% sure there. Your guess is as good as mine
10) another quirk on my car that I found that is easy enough for you to check is remove the two wiring harnesses from the two ECUs and examine the connector pins. On one of mine there was corrosion on one of the pins that took a toothbrush to clean. This, too, threw a code. Looking at and/or even breathing on the ECU's makes me nervous knowing how difficult/impossible it is to repair or replace these nowadays.
11) and finally, welcome to half the fun of owning a Diablo! 😎 lol
 

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1998 Lamborghini Diablo SV
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Discussion Starter · #7 ·
how does it run when fully warmed up, do the symptoms go away?
The hesitation and lurching at low RPM definitely gets better but not sure it completely goes away. I parked the car for about 3 hours this morning after fully warmed up. TX got a lot warmer today so it wasn’t very cold out like it’s been the last week. When I restarted the car, it took 2 cranks and a little throttle (as opposed to the 4 it took first thing this morning).


Sent from my iPhone using Tapatalk
 

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Take it on a long drive
 

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Take on a long HARD drive.

Check the carter motor operation, it's the unit that allows more air/fuel in when the motor is not at full operational. I would assume Josh would have checked that, since it sounds like the issue was present when he last saw the car. The car will nearly cool all the way in 3 hours. Caveat, I don't have 97, i have a 91 which has a different warm up system that serves the same function, and just read that the carter motors can be problematic, maybe talk to Josh about this. I think your car has a carter motor system (but not sure)

 

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and go back out tomorrow and see how it runs when fully warm. Does it stumble like you describe? turn it off, wait 5 minutes and turn it back on and see what it does. Try to determine if the problem is only present at warmup conditions, or is it there all the time.
 

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Discussion Starter · #11 ·
Take on a long HARD drive.

Check the carter motor operation, it's the unit that allows more air/fuel in when the motor is not at full operational. I would assume Josh would have checked that, since it sounds like the issue was present when he last saw the car. The car will nearly cool all the way in 3 hours. Caveat, I don't have 97, i have a 91 which has a different warm up system that serves the same function, and just read that the carter motors can be problematic, maybe talk to Josh about this. I think your car has a carter motor system (but not sure)

I did some research earlier and already came across that article on Lamboweb. Certainly could be the culprit regarding the starting issue but not sure it explains the bucking at low RPM. As far as if it has one, the 6.0's have it, so not sure why a 98 SV wouldn't.

and go back out tomorrow and see how it runs when fully warm. Does it stumble like you describe? turn it off, wait 5 minutes and turn it back on and see what it does. Try to determine if the problem is only present at warmup conditions, or is it there all the time.
That's a negative, Ghost Rider. I gotta work tomorrow. And everyday after that through Saturday. If I can manage to get out at a reasonable hour one of these days, I'll give it a go.
 

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Bonehead,
1) you should not have to give it gas to start, or to maintain idle, just FYI.
2) the ECU connections are easy to remove and you can switch them around. They are colored Yellow and White and are for left side / right side engine. You can inter-change L and R wiring harnesses and often do this to see if a gremlin will switch L and R in your CELs as a test.
3) Speaking of CEL's L and R, on the next key turn (always turn half-turn, wait for fuel pumps to finish and the dash lights to go out, then finish the key turn to crank the engine) go to halfway and wait for the dash lights. In the bottom right side of the dash pod are found the CELs. They should read "Check Engine L" and "Check Engine R" with the CEL on the top line and L and R respectively on the bottom line. If you are only seeing a single letter 'R' and not seeing an 'L' or 'Check Engine' wording then your lights are not coming on and therefore not warning you of any CEL's.
4) your state "inspection" is crap and will only tell you that you passed their test. Go buy on Amazon an OBDII reader - a good one is $100 or less - and this will tell you a lot. The car itself has a series of codes that are rudimentary and are known by counting how many times an 'R' or 'L' blinks in the dash. Good in a pinch or in a general sense, but an OBDII tells you all. You are lucky: in 98, Lamborghini listed specific cylinder misfires in their OBD computer diagnostic tests; in my 97, I get only banks 1-6 or 7-12 and have to diagnose from there. Early cars have none at all.
5) Geno has a good point on the Carter motor.
6) spend much time on this site reading and searching for prior issues/solutions. Guarantee your issue is already diagnosed in a thread on this site somewhere! Good luck and keep us posted on the resolution.
 

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oh, and Geno's second point, namely to take it on a HARD drive, is not a joke. These engines need and must be driven around past 5K RPMs (fully heated up first). They do not like prolonged low RPM driving just like they don't do well sitting for 6-9 months. Think of these like a human body: eating Cheetos watching TV all week bad; running 4x/week for 30-45 minutes good.
 

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1998 Lamborghini Diablo SV
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Discussion Starter · #14 ·
Bonehead,
1) you should not have to give it gas to start, or to maintain idle, just FYI.
2) the ECU connections are easy to remove and you can switch them around. They are colored Yellow and White and are for left side / right side engine. You can inter-change L and R wiring harnesses and often do this to see if a gremlin will switch L and R in your CELs as a test.
3) Speaking of CEL's L and R, on the next key turn (always turn half-turn, wait for fuel pumps to finish and the dash lights to go out, then finish the key turn to crank the engine) go to halfway and wait for the dash lights. In the bottom right side of the dash pod are found the CELs. They should read "Check Engine L" and "Check Engine R" with the CEL on the top line and L and R respectively on the bottom line. If you are only seeing a single letter 'R' and not seeing an 'L' or 'Check Engine' wording then your lights are not coming on and therefore not warning you of any CEL's.
4) your state "inspection" is crap and will only tell you that you passed their test. Go buy on Amazon an OBDII reader - a good one is $100 or less - and this will tell you a lot. The car itself has a series of codes that are rudimentary and are known by counting how many times an 'R' or 'L' blinks in the dash. Good in a pinch or in a general sense, but an OBDII tells you all. You are lucky: in 98, Lamborghini listed specific cylinder misfires in their OBD computer diagnostic tests; in my 97, I get only banks 1-6 or 7-12 and have to diagnose from there. Early cars have none at all.
5) Geno has a good point on the Carter motor.
6) spend much time on this site reading and searching for prior issues/solutions. Guarantee your issue is already diagnosed in a thread on this site somewhere! Good luck and keep us posted on the resolution.
Thanks for the insight. Yes, agree this or any 'modern' car with fuel injection shouldn't normally require some throttle input to start the car.

ECU's are behind the passenger seat, correct?

I'll definitely pay more attention to the dash lights in position 1. I'll check it tomorrow when I get home from work.

The state inspection does scan for codes through the OBDII port, whether or not they're relevant to passing the inspection or not. I did ask if it threw any codes and he said no. But I do have my own scanner and will check it again.
 

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Discussion Starter · #15 ·
@DiabloClyde forgot I took this video. Just after I got the car. This time it started on the first crank. You can kind of make out the lights on the bottom right. The 'R' illuminates but I don't see the 'L'. Hmmm......

 

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does the SV have the test to check for blinking codes on the CEL's? If so, i would do that as well, in addition to reading the OBD scanner results. Do you think you are missing a bulb on one of the CEL's? That is how the prior owner of my car fixed the "problems", by taking out the light bulbs....
 

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Discussion Starter · #17 ·
does the SV have the test to check for blinking codes on the CEL's? If so, i would do that as well, in addition to reading the OBD scanner results. Do you think you are missing a bulb on one of the CEL's? That is how the prior owner of my car fixed the "problems", by taking out the light bulbs....
Not sure if it does or not. If it does, I'll see if I can decipher them based on the Lamboweb article.
As far as a bulb, although not a great view of the dash lights, I don't see the 'L' illuminate, do you? I'll check it again when I get home and have a chance to plug in my scanner.
 

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on my 91, both left and right light up upon startup, then they go out (assuming there are no codes).

on the 91, you turn the key on and off 3 times (not starting the car), then the codes blink on the CEL's (if codes are present). you then use the table to decipher the number of blinks.
 

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I would start with the OBDII port and a data-logging application. Record the short/long fuel trim. Make sure the car is not running rich as that will ruin the catalytic convertors. Another test would be to put a fuel pressure gauge inline before the injector rails.

I don't think a bad carter motor would explain the hard starts and the stumbles on acceleration. Do you hear/see it do its calibration procedure after you shutoff the engine?
 
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