Help needed - engine won't rev
Turbo Mini Forums

Hoping someone on here can help me with an engine problem.
I've got my car booked in for an IVA test after 8 years and 3 months in build - it's a Mini Marcos for which I've built an MPi engine, with SW5i cam, big valve head, lightened flywheel etc., bored out to 1342cc.
Now the engine starts and runs reasonably but with not being able to run it on the road I've not had the opportunity to run it in/rev it out. When I did start the engine for the first time I did run it at the recommended 2000 or so rpm to bed the cam in.
But now I've got the test date (in one weeks time) and I'm going over the car to make sure it's ready, I've been blipping the throttle when it's warm and now discover the engine won't rev much past 2k rpm. In fact it dies down.
It sounds for all the world like my old escort on twin 45's - when you opened the throttle too quickly and gave it too much fuel it spluttered and coughs and bogs down.
The only thing I've done since first starting the engine (some 18 months or so ago) is fit a filter sock over the throttle body. I'll take that off and try it but don't think that's the problem.
If you open the throttle slowly it builds up to ~2200 and then coughs. If you open the throttle wide open from idle it picks up to the same then dies back.

Any ideas what it could be? Fuel pump not providing enough fuel? Air getting in the system somewhere? Sensor problem (I hope not).
I've got this weekend and evenings to get this sorted so any ideas welcome for me to check.

Cheers,

Few more details please.

Are you running MPi engine with Rover Engine management, or have you done something different?

HOSS

Same question really, is it running the standard MEMS ECU or something else.
If MEMS, do you have access to (ie, can you borrow) a suitable code reader.
Without seeing the ECU fault codes you are kind of blind.
Best guess from your description would be MAP sensor but without codes you could just be throwing money at numerous good parts.

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

Elf, Rod,
Yes -I'm running the standard MEMS unit.
I've taken the air filter off. No change, but I didn't really expect any.
I checked and I'm getting a spark from all leads. I pulled the plugs out - they were very black (but dry) which my old Haynes tells me could be overly rich. I swapped these over with those from the mini (a new set put in on Sunday) with no difference.
So following your advice I've dropped the car off at my friendly garage around the corner to have them run a diagnostic tomorrow.
I'll let you know what they find if anything.

8 years I've been building this thing.... Why now!

Maybe a fuel pump issue, but it could also be the wrong fitment clutch. Symptoms very similar

Hi Oli - yes I remember you well. I trust the club's still going well. Truth is enthusiasm has waxed and waned on this project, and with work and life getting in the way its taken longer than anticipated to get this far (and enthusiasm is definitely waning at the minute!). And I've still got the sportspack - almost 15 years I've owned it now. I built the MM up as an injection car so I could compare with Rover's version for electrical connections and the like. That car may be for departure if I can every get this one on the road though.

Sprocket - I did suspect the fuel pump it does make a strange whining when running (but then it always has). But the car has run cleanly in the past. In addition the plugs are showing signs of running rich/over fuelling - don't know if that would be the case if the pump was delivering too little fuel?

And all the clutch components are MPi (I did put the release bearing in incorrectly mind, but sorted that through help on here).

Elf, Rod - The garage plugged in their Bosch box of tricks. There were four fault codes showing - three related to the temperature sensor, one read inlet manifold pressure. After clearing these and starting the car again only the temperature sensor fault reoccurred. So that was changed out. They also diagnosed a possible air lock in the cooling system (probably caused by me situating the header tank slightly lower than in a mini due to the lower bonnet line on the MM. So this morning I raised the header tank, removed the return line from the thermostat housing and let gravity take its course, reconnecting the return line when coolant ran out of the thermostat housing. Hopefully this has removed any air from the system, but the garage did say the thermostat itself may have overheated and now be U/S.
Having done that this morning the car still isn't running much better - it wouldn't run above 2000rpm when cold/cool before bogging down.
When it had a little bit of heat in it, it did get to 2500-3000rpm before stuttering. On releasing the throttle the idle was barely able to keep it ticking over. I checked the sparks again and pulled one plug (photo above) and now the car won't start at all.

So symptoms are - it looks to be running very rich, runs smoothly enough on first starting but won't rev out, when warm it still won't rev out and when you close the throttle the idle becomes very poor.
Any suggestions welcome.

P.S. I phoned up on Friday and postponed my IVA (Friday being the last day I could do this without incurring penalties) until 18 July.
Also - does anyone know of a cheap OBD2 reader that would allow me to read the fault codes on an MPi? I know from previous the MEMS can be difficult to access (Sykes Pickavant I think did a system but its very expensive when they come up on ebay with the Rover module).

Thank again.

Edited by Cooper1999 on 9th Jun, 2018.

So far as I know the code reader for MEMS is quite specific, not just generic OBD2, hence my suggestion to "borrow" one.
On the TMF forum I know there is a list of people who have them and are willing to loan them.
To me the symptoms still point to MAP because if it doesn't read the actual manifold pressure and assumes atmospheric it will overfuel. A long, long time ago, I had a 16V K series Metro, same symptoms, and it was MAP.
But there are so many other possibilities, it really needs the correct code reader that can look at live data, not just the fault codes.
And if you go through the posts on TMF there are all sorts of other mechanical/electrical issues that occur regularly such as split small bore hoses on the manifold setup, wiring faults that cause sensors to read wrong, hence why live data is really essential if the basic codes don't really point to the answer.

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

Thanks Rod - I misunderstood a little I think.
I'll go over there now and look.

try it with the sock filter off ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Sound like you have made some progress, if you know there is no major issues with the electronics.

Did you say the engine had ran OK in the Marcos before, or has there always been a issue?

The one thing on your side is having a working MPi alongside it. Little secret, I have family who manage a Honda Hyundai dealership - when they have problems like this they will swap parts from a known working car, until they find fault. Not very scientific i know.

I would suggest going back to basics.

Is the exhaust free of obstructions? i once had a classic Saab Turbo with similar issues. Turned out the Cat had broken up and the core was blocking the exhaust.

Check all connections - vacuum pipes etc. If they are off an MPi, they are at least 18 years old now.

Is the throttle body in good order? I know there was an issue with the plastic ones distorting / breaking up.

You mention using a upgraded cam. Is it timed in properly? Correct me if i am wrong - but does the MPi not use a cam sensor for purposes of injector timing? Given the small widow the injectors have on a MPi, if the sensor is not getting right engine timing details, this will cause problems.

Does the MPi have any sensors in the air box, you might have lost fitting the sock?

There is nothing blocking / obstructing the inlet manifold? Dave Walker tells a tale of a difficult to diagnose issue caused by part of an air filter sock getting wedged inside throttle body.

One last thing - does your MPi rev past 2k when stationary? A lot of modern cars won't rev above 2k when stationary.

HOSS

Elf, the engine had run nicely in the MM when first installed/connected up. I ran the cam in (SW5i) for 20 mins or so at the recommended ~2500rpm and have had it running numerous times since (always try and let it warm through rather than just drive it out the garage and switch it off). Unfortunately not being able to take it out on the road doesn't allow me to test it more thoroughly. I hope the cam timing hasn't slipped (fitted with a vernier which I took my time to time in spot on (107 degrees from memory, although my memory's poor at the best of times!). And yes there is a cam sensor fitted, but again not sure how I'd test that (for serviceability) other than with the Rover test kit or component swap.

Swapping components over occurred to me yesterday too while looking under the bonnet of the mini. And I also thought there could be a split hose or something letting in too much air which in turn could make the ecu deliver as much fuel as it could - hopefully any damaged hose/pipe will be apparent when swapping things over (starting with the MAF/MAP I think).
(This link is very useful to an electrical/electronic biff like me - http://www.turbominis.co.uk/forums/index.php?p=vt&tid=600990 ).

There isn't any electronic connections on the original airbox (which I did want to use to reduce some intake noise) as I realise the sharp edge to the TB isn't very efficient for airflow. I've tried to run the car with the foam sock on and off.

The TB by the way is a 52mm alloy job that I swapped over from the mini (that's 1330cc, SW5i, ported head) which a session at SRE proved didn't really offer any improvement over the standard 48mm item. I was hoping the additional 12cc of the MM might make more use of it . (And I wouldn't have any future problem with distorted plastic)

The car isn't fitted with a catalytic converter - not required for IVA unless the vehicle fails emissions (I asked the IVA Tech helpline). And the mini revs throughout the rev range quite freely when stationery.


Interesting aside, when I ran the mini at SRE on the rolling road (on a standard 1275 bottom end but polished big valve head at the time) the standard ecu caused the car to run lean over about 4500rpm. The ecu couldn't deliver any more fuel. As a consequence I rarely rev it out that far (which negates the fitment of the camshaft really). If we can get the MM through IVA and get the engine run in, it might be a case of investigating alternative ecu/fuelling so I can make better use of it in this car as the next project.
Oh well.... back to trying to getting it sorted

The other things to check is the is no leaks on inlet manifold which could upset the MAP sensor.

Also as Marcos is not metaled bodied are all the grounds on the electrics are good.

Think back to what you did to the car since it was last running correctly. Might you have knocked something?

Regarding the can sensor, I guess the car won't run if there was a fault with the actual sensor and the code read should have flagged it up.

Might be worth checking if cam timing has moved, once exhausted everything else.

HOSS

How old is the fuel in the tank, modern fuel only lasts a couple of months before it goes off.

As part of checking the basics might be worth flushing through with fresh fuel and change the fuel filter. Could explain sooty plugs.

HOSS

If you google MPi won't rev, quite a few other people have had this issue.

HOSS

Thanks Elf - I'll do that now.
It wouldn't appear to be the MAP sensor at first check. Swapped it with the mini's unit and no difference.

Doesn't appear to be the air inlet temp sensor either.
So No. 5 & 6 checked in the attached: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=600990
And no sign of poor hoses in 1, 3 and 4 either.
I have had to make another hose fit for the servo (No. 2) but sealed that when fitted the first time.

Googling has thrown up perhaps more questions than answers - seems people are chasing the problem without getting to a single solution. This is going to be bloody annoying, I can see!

I'm going to phone Green & White tomorrow and see if they have the Rover gear to check the car out. Hopefully they will but that'll give me the problem of getting the car to them if they do.

Yeah people do just swap bits till they find the issue, not very scientific.

I think check basics, make sure all connections are good, pipes are good, then move on to testing componants.

How old is the fuel in the tank? The ethanol in modern fuels soaks up moisture and creates a sludge. If it is more than 3 months old might be worth draining down, change filter, and run a good fuel system cleaner through, like cataclean.

Super unleaded from a branded petrol station has a higher level of detergents. Worth tanking up with that.

HOSS

Fuel is Shell Super unleaded (this is all I use in the mini after I got the head skimming calcs wrong and ended up with a CR of around 11:1. The MM engine is around 10.5:1).
Fuel is less than a couple of months old. I don't keep much in the tank topping up regularly as required so that it doesn't become stale.
I might drain the tank and change the filter anyway - nothing to lose by doing so. And perhaps separate the exhaust as there seems to be some thought that excessive back pressure might be a cause (can't see it on this car though with no Cat to break down).

Try the low hanging fruit - new plugs ?
And of a higher heat range possibly?

Another long shot, as it's been such a long project the injectors themselves might be gummed up and not flowing enough fuel at higher revs.
Doesn't match the sooty plugs though, I'm still on MAP but maybe the wiring rather than the sensor itself.
You really need live data to see if MAP is 100kPa not running and a suitable low value for idle and goes up as you rev it.

This might be worth a shot, http://memsdiag.blogspot.com/ (if you've got an android phone and can make up the required cable).

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

Woo Hoo.... A bit of a break through!
I spoke to Lance at Green & White today who've helped me out numerous times over the years. After describing the symptoms while he hadn't come across this exact problem he did suggest checking to see if the engine was drawing in air somewhere causing the ecu to try and add fuel. (I said I couldn't see any poor hoses). He said he'd come across quite a few MPi's where the seal between the inlet manifold and the head had been shit, having to have the head and mating face of the inlet manifold skimmed/stoned to try and get them to seal.
To check he suggested opening the throttle just to the point where it was stuttering and spraying the inlet/face joints liberally with carburettor cleaner - if the engine picks up, you're sealing the air leak and that's the problem (poor sealing allowing air to get in).
So with fire extinguisher to hand that's what I did and guess what - that's the problem. Happy days.
Some more investigation needed - why has the gasket suddenly given way? Has something happened to the inlet manifold?
And I need to find a reliable way to clamp/seal the head/manifold (I am using the correct metal faced MPi gasket by the way). After all, the cars only done 1.1 mile (perhaps about 90 minutes running in total).
But at last a step forward (Hope I'm not being too premature)

Rod - I'm still going to have a crack at that mems diagnosis 'app'. I think this might be the catalyst (kick in the arse) I need to understand the electronics theory of injection/ignition more. And perhaps might help me understand what I want to achieve with any future developments of the car re. different ecu, improved fuelling control etc.

But thanks ALL for your help and suggestions . I hope this is the problem/solution but once I've looked more closely at the gasket/sealing I'll be sure to put an update on here.

Thanks again.

What gasket is fitted?

Often cheap ones are fitted, this is the type you want.

http://www.minispares.com/product/Classic/...ack%20to%20shop

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

Jonny - that's the gasket that's fitted. I've ordered another couple of them from minispares.
Rod - I've tried tonight to clamp up tighter against the inlet manifold making some 'L' shaped metal packer pieces but that hasn't worked. I'll try the same exercise with one of the new gaskets when they arrive.