MPI query, massive missfire at 5k rpm
Turbo Mini Forums

My car has a full stage 3 kit (bigger head, 1:5 full roller rockers, k+N filer, lcb and rc40 system)

As per the thread title, when giving it some beans the car gets to just under 5k (when the car is just coming onto song) then there is a loud pop (misfire) and the car seems to go into limp mode and dies, it wont rev and the engine sounds like it is choking up, if i pull over and let it tick over for a minute then pull away its ok again the car does not cut out completely but runs like a bag of shite, if i tootle about its perfect its just when i open up the taps.........anyone any idea's ? i am new at injection mini's

is there any way of mapping the factory supplied ECU ?


cheers

Richie

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MikeRace, Mini13

Sounds like fuel starvation. Has the fuel filter been replaced?

no idea, only had the car for 5 days

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MikeRace, Mini13

also sounds similar to my ignition issues with my carb mini. plug leads where the cuplrit.

Have you given it a proper service?

I'll go with the fuel filter too. Mine had its factory filter on when I got it at 60k-ish.

Changed it and the car would rev much more freely.

The filter is probably even more critical on a well modified engine. Do you know if the fuel pressure reg has been modified?

It was a common mod on the mpi's to increase the fuel pressure slightly when the stage 3 kits were fitted to stop them leaning out at high revs.

If something is worth doing, it's worth doing half of.

Wasn't the common mod crushing the reg in a vice slightly to increase the spring pre load?

Correct Tom! Another one was to dismantle it pack the spring. Or you can replace it with an external adjustable FPR.

If something is worth doing, it's worth doing half of.

Fuel filter or plugs and leads....

Its a good place to start.

AlexF

Did someone else not have similar spec/problem on here about 4weeks ago? It sounds to me like it is just not coping to well with all the mods. I thought these ecu's were quite tempromenta when it came to tuning.

only thing i have done is check oil and coolant it will get a full service when the body work is finalised is there a plug in device i can use on these cars ? Like the ODB 2 system on the volvo ?

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MikeRace, Mini13

The mpi mini has a different protocol to standard OBD you would either have to find a garage with the rover testbook or i think sykes and pickavant's ACT unit works with the mini but you need the right card/cable.

Have you pulled a plug and had a look at it out of interest?

If something is worth doing, it's worth doing half of.

Have you pulled a plug and had a look at it out of interest?

as john says richi, also dont rule out the coil pack

nah i am on the train on my way to peterborough will check when i get back

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MikeRace, Mini13

Another thought. Make sure the plugs are NGK BPR6ES.

If its not a resistor plug, the ECU doesnt like them.

The other thing to look out for on the SPI/MPI's is the CAS or crankshaft sensor as it controls what the engine does with the ignition as its providing the primary rpm engine speed reference.

A simple way to check all is within spec is to measure the resistance across the two pins inside the blue connector socket, found just above the starter motor on SPi, presume the same on MPi.

If my memory recalls, the figure should be something like 1700 ohms but don't quote me on that, look it up in a Haynes or do some searching.

I had one on a 1.3 SPi which broke down and was giving 1150 ohms with exactly the same symptoms as you have quoted.

Its a very simple check for piece of mind.

A new one will set you back about £45.

PS: The CAS is usually also the thing that goes wrong when you have an erratic idle or if your engine stalls when stopping at T junctions.

If all else fails, borrow a decent dizzy and slip it in, take it for a spin to see if the misfire remains then you can at least separate fuel from sparks. Assuming of course the advance curve is somewhere handy.

Good luck.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
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You can't fit a dizzy to an MPI, it has no hole for one.

psml dunno where i would slip it in then.......dont normally get confused with matters like that.

the car idles perfect does not cut out and pulls great to 4500 rpm, will get it up on the ramps and have a check.

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MikeRace, Mini13

or get it on a dyno :)

AlexF

and the crypton tune at the same time :)

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

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MikeRace, Mini13

took the plugs out and they were all ok, leads appear new and are not corroded on the contacts, nothing appears out of place.

i went out again today to deliberately induce the symptoms, i notice that after the pop the car "fluffs" and wont rev, if i pull over and come to a complete stop i can pull away straight away and the car is ok again ?

Edited by Richie on 13th Aug, 2009.

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MikeRace, Mini13

still cant find anything amiss.... its like me volvo i will pop it down for a "plug in and tell me a story"

just hope its not a sensor
http://www.minispares.com/Product.aspx?ty=pb&pid=37762

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MikeRace, Mini13

Have you changed the fuel filter yet? As if not I wouldn't waste your cash on getting the codes read until the cheap things are eliminated first.

Have you actually found somewhere that can actually read the mini's codes then Richie?

When I had mine I couldn't find anywhere! Then when I got rid of it my brother got all the kit to do it at his garage.

If something is worth doing, it's worth doing half of.