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Mike, Mitsubishi Mechanic
Category: Mitsubishi
Satisfied Customers: 39198
Experience:  34 + years of Vehilce Repair - Electronics and Diagnostics
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ive tested coil packs..fuse blow or is it the engine management cpu

Resolved Question:

my carisma is misfireing ive tested coil packs they seem ok
is there a fuse blow or is it the engine management cpu
Submitted: 5 years ago.
Category: Mitsubishi
Expert:  Mike replied 5 years ago.
Hello and Welcome to justanswer...

Its not going to be a fuse no - there are no fuses to cover that circuit...

You dont mention if the EML - engine management light is on on the dash while the engine is running - but of it is - a plug in diagnostic test should be done which will locate the fault quickly and cost effectively...

Even of it isn't on - a plug in live data test will find the problem quickly too....

If you are positive the coils are ok - and the spark plugs are ok.. Check the wiring to the coils very carefully - often the wires to them break or you get bad connections so check those carefully as I say..

Anything amiss that you find would need to be repaired and then go from there...

If you are still struggling, you need to narrow down to exactly which cylinders are misfiring... and then have a compression test done, to see if you have a mechanical problem in the engine - burned valve seats for example will cause a misfire...

Too - check carefully for any vacuum leaks in the pipework around the engine - check carefully and especially the small bore piping..

If all is well as above - then the Cpu could well be suspect and will be if one or more of teh coils are not firing... You would need to contact a Ecu / Cpu repair company to send your unit too - to be tested and go from there..

So work through as above and you will get to the bottom of this one..

I Sincerely XXXXX XXXXX have helped you - but do ask me if you need anything more..

Kind Rgds, MIKE


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Customer: replied 5 years ago.
hi ive tried a second hand cpu it made no difference. the engine light flashes on and off and it doesn't rev past 3000 revs i had a mechanic out to do a diagnostics test but could not connect with the cpu he said there was no power from the socket could there be a bad earth or short in the wiring
Expert:  Mike replied 5 years ago.
Hello again... thank you for your reply..

As you have the EML - engine light flashing.. this means there are "faults" detected and logged in the Cpu 's fault memory...

This is why the engine will not rev over 3000 rpm as well - because with the EML on - the system is in LHM... "safe" or limp home mode...

This is a default set of engine management values to protect the systems while the "faults" exist...

You now need to have the diagnostic test done as I outlined extract the stored fault codes from the computer....

Once these are retrieved, that tells you where the fault is - which can save you hours of fruitless searching... and then the fault whatever it is, can be sorted out properly..

So thats the way forward on this one now....basically...

I note what you say re the lack of power / feed at the diagnostic socket... this will happen for one of three reasons.. either a blown fuse - for the diagnostic socket... a bad connection at the pins / in the socket ...and wiring to it - or a fault in the Cpu.

There is another reason why one cannot get connection - and that is a very common reason... the operator not using the correct equipment for the system / either hardware or software...

However.. you have a system here that you can access the codes without equipment - using whats called flash codes...

To do this - you use a wire plugged in / inserted into pin ONE of the diagnostic socket.. and earth it on a good earth point.

Then - switch the ign ON... and count the flashes of the EML.... the flashes relate to fault codes...

No flashes mean no faults found - but watch it very carefully - you will see a sequence of flashes - that will equate to a fault code... it can take several mins of watching to get the idea and determine whats happening - but you will soon determine that it is flashing definite fault codes....

Once you have the code/s - you can then go from there..

I hope that all helps you further -- Please dont forget the ACCEPT button for me ... and , if you do need any help after - just come back to this post and use the reply button thereafter and I will get back to you again.

Kind Rgds, MIKE


  • >>>>>>>>>Please don't forget ....Please press the ACCEPT button if you are happy with my answer/advice given - as that's how I get paid for my time, knowledge and expertise given. Thank you.

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