Hi All

Just come back from a spirited drive of about 20 miles. I was pulling hard to overtake a line of traffic doing about 110mph in 4th gear (manual) when the car cut for a split second, just like the engine had been turned off for about 1/4 second.

Quite a jolt, but Ok for the remaining 5 miles home, although I did back off bit.

Any ideas?

All gauges reading OK, oil pressure 3.5 bar at idle when I got home (Hot)
Nothing obvious, to see, checked all earths, and sensor wiring; all sound. Vacuum lines all check out. Fuel rail pressure good (I have gauge fitted)

Full service about 1800 miles ago, complete engine rebuild about 2200 miles ago. Oil clean, all levels correct. No odd noises, revs cleanly, exhaust clean.

John
'86 S2 Manual Euro (twin dizzy)

 

Hair ball is my guess.

 

Seriously though... there are very few things that would make the car loose power like that. You didn't happen to hit the rev limiter by chance, did you?

 

No not the rev limiter, this was a total cut, rev limiter on my car is quite soft in its action. Quite used to that!

I'm thinking dodgy connection somewhere, either ignition cut (most likely, due to speed of cut) or maybe injection system cut.

John

 

It's good to do Wally's ground refresh once a year or so.
https://rennlist.com/forums/showpost...8&postcount=33

 

Engine been out and rebuilt, ALL earths are cleaner than a VERY clean thing.

 

When you say, "Quite a jolt" do you mean that literally or figuratively?

Anyway... here's what I can think of that would kill an engine like you described
-Bad Ignition switch
-Short in the injector harness
-Faulty crank position sensor
-Faulty LH
-Faulty EZK - rare

I or most likely others may come up with more.

 

Sounds like some sort of an ignition cut off. Usually if it’s sudden and abrupt it usually is spark, more precisely the lack of it that can cause this.

 

I don't know... the Rev limiter works by cutting fuel, and I can tell you that it's pretty abrupt. When SharkTuning I set the limit to 5000 rpm and the fuel to kick back in at 4000 RPM. I'll tell you it sure felt like someone cut the strings to the car when I hit that limit.

 

Thanks Andrew,

I think I will do some testing of the engine harness, thay take some grief when threaded off and then back onto the engine during a rebuild. Maybe I have an intermittent break/short.

The joys of trying to find an intermittent electrical fault!

John

 

Yeah BUT you are running what??? 450hp, so of course any hesitation in the engine will feel abrupt.

What I was trying to say that fuel cut-offs feel a little softer than ignition cut-offs.

 

Oh yeah... I suppose that does make a slight difference.

 

Did the instruments drop out at the same time?

+1 for ignition switch as a possible. I'd wiggle the key before I started wiggling the harness.

Any chance one of the grounds is clean but not tight?

Have fun. ;-(

 

At a bit over 6,000 rpm, my car hits the rev limiter and it's absolutely abrupt. As it slows down a bit, gas resumes and it jumps forward, then hits the limiter again and cuts abruptly. I only do this when testing the car after working on it. The first time it happened I about browned my trousers.

H2

 

I had a faulty LH relay cause the same symptoms, eventually got so bad that the engine would die without warning. Start there, it's easy to do.