Lamborghini Talk banner

1 - 20 of 57 Posts

·
Registered
Joined
·
34 Posts
Discussion Starter #1
It's been a while since I last posted. The car has been running like a swiss watch for the past 4 years. Pretty good for a vintage exotic!

This spring when I got the '92 out she started cutting out at about 5500 rpm under heavy throttle. She pulls perfectly and predictably up until about that point and then she starts backfiring and missing. I had a buddy on a bike tail me and he said he got a smoke show when I matted it (burning rich, not oil). This issue came on all at once, it did not get worse gradually.

The engine in obviously in fine form. No smoke or black tailpipes. Runs perfectly until that point on the tack. Seems like a sensor or vacuum issue to me but looking to some advice.

Thanks for any thought on this!
Peter
 

·
Registered
Joined
·
1,986 Posts
sounds like you are losing a bank at high RPM's. Maybe pull the plugs and see if there is something to be learned?

can you recreate the problem while the car is stationary (ie, reving in neutral) or does it only happen under load.

might be a coil amplifier failing.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #3
Thanks for this.
I will check if it happens in neutral (after I warn the neighbours :).
I will take a look at plugs tonight as well.

I was wondering about the coils as well. The strange thing is that the issue is so consistent and the car idles and runs perfectly under 5.5k that it seems odd that a coil would be the issue. I replaced the coils about 3,000 kms ago so maybe it is a connection.

Thanks again. Updates to follow.
 

·
Registered
Joined
·
1,986 Posts
not the coils, the amplifier on the other side of the coils. Coils dont fail, the amplifiers do. Did you replace both the coils and amplifiers together as a unit?

c
 

·
Registered
Joined
·
1,299 Posts
coolant sensors?
I had a similar problem many years ago and this was nearly impossible to diagnose.
You throwing any codes?
 

·
Registered
Joined
·
34 Posts
Discussion Starter #7
Great questions. I had a coolant temp sensor fail about 3 years ago. What was happening in that case was that it would run very rich and lose power intermittently while creating a lot of smoke. Like you, it took me a long time to figure that one out but the issue resolved as soon as I replace the sensor. In that case, it was throwing a code.

I'm getting no engine codes on the dash right now and they have worked in the past.

I never did replace the coil amplifiers (was not even aware of them). Something to look at.

I just ran out to the garage and ran it in neutral. Here is what happens when I floor it. It's right around 5500 rpm that it just won't go any higher. If the car had a valet setting, this would be it :)


I am going to go check my engine lights again.....
Thanks very much!
 

·
Registered
Joined
·
34 Posts
Discussion Starter #9
Thanks. Will give that a shot.
I confirmed the check engine lights are working but no codes.
 

·
Registered
Joined
·
1,986 Posts
Not the coils, maybe the amplifiers, but likely not. That seems like something is telling the LIE "shut 'er down"....
 

·
Registered
Joined
·
34 Posts
Discussion Starter #11
That is exactly what it feels like. The LIE is just cutting power. It's very consistent and predictable.
 

·
Premium Member
Joined
·
700 Posts
By any chance does your car have a rev limiter installed? Could it be a matter of throttle position sensor reading that it is at some limit?
Just diagnosing this in my brain but certainly not that I’m a mechanic, but it seems to me when you hit a recurring uniform RPM something causes an electrical signal to start shutting down. I think in my mind that something is rotating and either by vibration or by electrical impulse something is coming loose at a certain RPM almost like your distributor cap is loose and therefore starts to pull away from the connections. I have not pulled one apart so please forgive the neophyte idea but could the shaft on your TPS be slightly bent and therefore it starts to gap the electrical connection above a certain RPM? finally, I don’t think it would be heat related because you mentioned this happens repeatedly when you hit a certain RPM. A heat sensor would hit a certain temperature and start to shut down the engine at lower RPMs as the car got warmer and warmer. good luck.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #14
Interesting thoughts. It does behave like a rev limiter. I think what I'll do next is rev it manually to see if I can see anything strange happening.
Agreed that it's not likely temp related since it happens regardless of engine temp. Will keep looking.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #18
Did a bit more homework and the prime suspect at this point is the throttle position sensor. Reviewing the symptoms:
1) No issues at all until about 5600 rpm. Starts great, idles great and drives great as long as you don't go for hooligan mode (I love hooligan mode)
2) No big issues at 5600, she just won't go faster. I can't repeat that smoke issue that my buddy on the bike originally reported
3) Problem is the same when driving (under load) and when in neutral
4) Does not seem to be bank specific. Both banks seem to be in sync
5) No engine codes thrown

I will pull the TPS off tomorrow and test it. I'll report back with my findings.
 

·
Registered
Joined
·
1,986 Posts
dont pull that TPS off, unless you are certain you can get it back into spec (ie, get it set back to the right degree angle / voltage reading.). Your car sounds really strong, so its running well, i wouldnt remove that TPS.

you can test it on the car - search around if you cant find how to do that i will tell you.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #20
Thanks for the safety tip. I'll follow your advice and try to test it in place. I assumes that involves unplugging it and hooking up an ohmmeter to the contacts? If there is a better way I would really appreciate pointers.
Thanks!
 
1 - 20 of 57 Posts
Top