Power loss puzzle

Hi all,
I hope someone can help.
Ive had my jimny for 5 years now, its 10 years old, never a thing wrong with it besides normal replacement stuff, brakes tyres etc.
Mid JAnuary as i was coming off a motorway had a sudden loss of power, engine started shuddering, limped of the slip road at 20mph. Called the AA out, they checked it all, no leaks, nothing broke, no faults on computer. Was low on oil, so we topped that up. It started up fine and worked perfectly well for two weeks and then it did it again. AA man said at time it probably needs a good service (as i havent been able to afford it past two years) but all looked good otherwise. Took it straight to my garage who gave it full service. Sounded sweet! On way back from work next day it did it again! So straight back to garage...
Oh and it took half a tank of petrol over 25 miles.

now 2 weeks later i still havent got it back!

They have done every test and cannot find a fault, drove it and it wont go wrong for them.

So the only thing they can think of is that it may be the fuel pump but the only one they can get is £450, a bit expensive if its not that that is wrong

a, anybody got any ideas?

b, anybody selling a fuel pump cheap?

I want my JJ home

Pam x

p.s. I am an archaeologist and do take my J out to play with work

I would suggest the camshaft sensor at the back of the head if it is a G13BB engine. That was the intermittant fault with mine. Part only cost about $50 and it has been right ever since.

Thanks, will tell them to look at that

Mines a M13AA engine but from reading other posts i guess it will be the same.....

If it's the m13a when it lost power did the engine light come on and the rev counter jump about? If so it's the crankshaft sensor near the alternator

No, no lights came on and i didnt see the rev counter jump, and i believe they have checked the exhaust

As the others have said, the usual mysterious power loss & lumpy engine without the EML, but it gets better when you turn it off is crank sensor.

A constantly increasing power loss (no EML) is a blocked catalyst, ocasional loss, with a rattling sound, is broken catalyst, and the bits are moving around, blocking it under load.

Continual increase in fuel consumption, possible lumpy running (no EML) is front exhaust sensor out of spec, but not failed yet.

Huge increase in fuel consumption is likely a leak in the return pipe, at the bend against the chassis under the drivers feet.


Rough running when hot (no EML) can be faulty plug, plug hole full of oil, lead breaking down, faulty coil. (The ECU senses a spark problem, but doesn't notice a HT fault somehow...)

Would have thought that a garage would check these though...

They have already checked the camshaft sensor, no faults on computer. BUT they are going to swap it as it comes back as the most logical answer to the problem. They have checked everything and gave it a good service so...

Thank you all for your help

Pam x

None of the things in my list will show on the computer.
You would think they ought to, but in my experience, and that of others on the forum, they don't.

If a sensor is out of spec, but still reports that "everything is awesome" when it isn't, the computer will never know.

Thats the theory they are working on lol. Thanks

I had a similar problem. I changed the spark plugs and hasn't done it again.


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