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Discussion Starter · #1 · (Edited)
Hey Guys,

I've been trying to solve this issue for over a year. My car refuses to rev over 6,300 rpm's. Feels like the car just cuts the power at that point in time (thought it was ignition issue but clearly not after you see list of parts changed below). It runs like a champ except for this issue.

Replaced/serviced the following parts over the past year and a half with zero improvement.

Spark Plugs
Spark Plug Wires
Coils
Coil Amplifiers
Distributor Cap (Brass)
Distributor Rotor
All Phase Sensors to include TDC Sensor (a royal pain to replace)
Fuel Pumps
Pre and Main Fuel Filters
Pulsed brake cleaner through all 12 injectors with 12v power supply
Coolant Temp Sensors
Lambda/Oxygen Sensors

Car had a water pump failure in 2019 and at that time I had the following work done.

New OEM Waterpump
Bosch Alternator
Sanden AC Compressor
New Drive Belts
Converted AC to R134A
New Coolant Hoses

I'm really at a loss as to why this is happening. Car has not thrown one code the entire time it's been doing this. So I'm literally shooting in the dark with the repairs.

Please advise if anyone has had an issue like this. Thanks in advance.

-Blake
 

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Discussion Starter · #3 ·
I've considered that but the car is idling at same rpm as before this issue occurred. Additionally, if rev'ing in neutral it will go over that if there's not a load on the engine. I'm sending injectors off for a cleaning with Evan's Automotive to see if that helps...maybe the pulsing I did wasn't enough pressure.
 

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Discussion Starter · #7 ·
How about regrounding/checking all ground straps. Where do you live?
I was thinking about doing that. I’ve seen people with similar issues do on here and didn’t seem to help but willing to try anything at this point. I reside in Florida.

I’ve inspected the 3 at the rear of the car. Aren’t there 2 more somewhere else?
 

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Pull them off and grind surface clean. Takes no time. Another one behind battery cut off, get that one too.

and the ground for the LIE. Have you delved into that realm. Also sent you a PM
 

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Discussion Starter · #10 ·
I think there are 4 at the rear aren’t there?
I’ll have to check. I saw the ones on each header and the one on the rear differential. I’ve also had the car fitted with an LOC exhaust and Cat Delete but if anything I would assume that makes it run better. I noticed one of the ground straps had a little bit of fraying on part of the weave but 99% of it was in tact.
 

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Discussion Starter · #14 ·
And amplifiers, coil and amplifier? also grounds under/near center fuel rails, check those
Replaced Distributor Cap with brass one from Evan’s Auto and Rotor from them as well.

Changed both Coils and also the amplifiers that sit on top of the coils. DAC4608 coils and Regitar XM31 amplifiers based on what you had recommended in another thread I made awhile back.

We just pulled off injectors and those grounds were secure.
 

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Discussion Starter · #16 ·
Swapped in A59GC Champion plugs and gapped to .5mm per workshop manual, discovered previous plugs weren't torqued all the way down properly. Car is running much better. Not perfect, but a lot better. It popped a plug wire on the drive so letting car cool down and then re-seating the plug wires. They're very hard to get to seat properly for some reason.
 

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Swapped in A59GC Champion plugs and gapped to .5mm per workshop manual, discovered previous plugs weren't torqued all the way down properly. Car is running much better. Not perfect, but a lot better. It popped a plug wire on the drive so letting car cool down and then re-seating the plug wires. They're very hard to get to seat properly for some reason.
Thats great that it's running better! I've had a lot of issues getting my plug wires seated right. Some go on perfectly but others I have a harder time knowing if they are seated right or not. Is the revving problem now fixed? If not did you check any of the grounds at the gauges? Are there any other gauges that seem slightly off? You could also try the diagnosis procedure checks of the ohms of the infection and ignition systems in the workshop manual. With these you can check the quality of at least some of your grounds, sensors, relays, wiring, etc. Just a thought. Keep us posted and good luck!
 

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Discussion Starter · #18 ·
Update car now misfiring when it’s up to temp for a few minutes, runs better when initially up to temp for a minute or two at higher rpm’s. Forgot to mention I swapped out DAC4608 Coils for Original Magnetti Marelli that I’ve had in storage for a year that came on car originally. So looks like we are still chasing the issue unfortunately.
 

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seating plug wires is a challenge, i made a special tool out of 90 degree needle nose pliers that allowed me to seat them all the way down. Did you make you own plug wires, or did you buy new. Maybe double check Ohm, wiggle around etc. Sounds like spark is giving up at high RPM's. Do you have anyone near you that you can do an LIE swap?
 

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Do you have "Check Engine" light on? What does they say?

I would think it runs rich, so manifold pressure sensor faulty/wrong one, or vacuum hose loose/broken from plenum or interion vacuum tank.
 
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