Help needed - engine won't rev
Turbo Mini Forums

So, I've tried to sort the car this weekend - problem looks to be different thicknesses on the flanges of the exhaust and inlet manifolds.
New MPi gasket, ali and steel packing pieces made from what I have lying around (different thicknesses), 'old' style gasket made into packers (thought this might squash up). All I've succeeded in doing was raising the revs at which it dies. At least this seems to prove what the problem is.
Tomorrow I'm going to call Green & White and see if they can pick the car up and sort it (they've had to machine the manifolds before to get a good seal).

And to top it off I went out in the sun on the motorbike today and ended up getting a rear puncture! And I've only done about 150 miles on these tyres

So I've removed the inlet manifold and used a steel rule to ascertain how 'level' the manifold legs are - lot too bad as it turns out. I'll linnish these as level as I can anyway now it's off the car.
I also plan to loosen off the exhaust/exhaust manifold so that, when I refit, I know the joints to the head are as sealed as they can be.
But I've taken out the MAP sensor and it was covered in soot.

When cleaning this I noticed that part of the sensor rotates and appears to be sprung. However it doesn't appear to return to the original position. Now I'm not certain how this sensor works so don't really know if this is normal or not. Anyone know?
Also I'm wondering if the lambda sensor ( a new pattern part I bought when building up the car) could be 'contaminated' and clogged up. Could that happen? (Sorry - I'm a bit of an electronics biff)

That's not a MAP sensor.....

Although I'm not that familiar with the MPI inlet manifold design I'd be pretty sure that's the IACV (idle air control valve).

It shouldn't be sooted up unless..., well lots of bad reasons.

Post a photo of where this bit came from.

Schrödinger's cat - so which one am I ???

Rod, I called it the MAP sensor after looking at this:
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=600990
I realise now I've got the wrong end of the manifold (too much rushing around yesterday). This is a sensor bolted into a mount which in turn is bolted the end of the manifold (near 1 & 2 in the attached.
Sorry for the confusion!

Okay, so with some help I've improved the situation but not cured it totally.
The problem (or part of the problem) wasn't over fuelling but fuel starvation. I must've kinked a pipe while messing around underneath restricting supply. Only when a fuel pressure gauge was fitted did this become apparent. Ho hum...
I'd already linished the inlet manifold and created some better packing pieces to seal the exhaust/inlet manifold better.
So now the engine revs out to ~3200rpm quite cleanly and then stops, sounding as if it's hitting a rev limiter (as opposed to dying away as it did before). I don't have the fuel pressure gauge anymore to test this but have come up with another theory I'm hoping someone can confirm.

The car is fitted with the same rev counter it came with when I bought it - this is a green faced unit. The car idles according to that rev counter at around 850-900rpm. It then revs cleanly to 3200rpm.
Is it correct that, due to the wasted spark MPi ignition that a carb car rev counter would record half speed? That is, the car could be hitting the rev limiter (which on the MPi is at 6300rpm-ish)?

I must add - the car doesn't sound to me like it's revving it's nuts off (so really do think its limiting itself to 3200). I've ordered a strobe lamp with digital rev counter which will confirm this from ebay, but just thought I'd ask if someone could confirm if I'm barking up the right/wrong tree, so to speak.

Thanks,

You "might" be right but I would have thought the difference in sound would be obvious, or just drive it and see what MPH you get for the indicated RPM in any gear.

The strobe lamp you have ordered may give the wrong RPM output anyway, a lot of them don't handle wasted spark correctly either. I only use a "dumb" one for that reason.

Schrödinger's cat - so which one am I ???

Thanks Rod. To my ears the car isn't going as hard as the rev limiter but I'm grasping at straws.
Unfortunately I can't take the car out as it's not tested (IVA now booked for end of August) to check the speed v's revs.
I'm away for a couple of days so will try and see if I can get an answer when the strobe arrives.
Cheers,

Jack up the front, put it on secure axle stands and "drive" it like that to compare RPM to indicated MPH.
(you'll also find out how well balanced your front wheels are......)

Schrödinger's cat - so which one am I ???

Tachometer on the crank pulley to compare against the rev counter?
Shane

I had a similar issue when my supercharged mpi was first built. Weirdly it only ran shite when the bonnet was shut! After lots of messing around and thinking something was shorting electrically it turned out to be a trapped fuel hose. It was. The return hose which meant fuel pressure was way to high and it overfuelled terribly. Might be worth checking, what regulator are you running? The standard one? If so may be worth swapping that out with a known good one as well.

Hi Andy - yes, I'm running the standard fuel regulator.
I got the strobe with rev counter, checked this on the mini (which looked to be reasonably accurate) and then tried it on the Marcos. At idle it was recording roughly the same as the rev counter but as soon as you revved the car the strobe rev counter went to zero. Strange.
So now I'm wondering if there's a problem with the plug leads (as the strobe clamps on to no. 1 lead to record the revs).
As it is I don't think I'll be checking much for the next 5-6 weeks after having broken my wrist on Thursday (so sitting here bored, trying to type one handed). How did I break my wrist? By crashing my mini of course - the one I was trying to sell!

Bugger

Guess I'll be putting the IVA test back then. Again!

I'll let you know how I get on, eventually, in testing the fuel reg.