Limp mode loss of power 05 plaste

I've got a 05 plate jimny that has a intermittent power loss issue, it suddenly loses power but will still run ropie if i pull over and turn it on anf off a few times it revs up and away i go...at mot it failed its emissions but they kindly passed it:) its had a new lamba sensor because that wasnt working.any ideas anyone..thanks in advance

Mark

If you have a new Lambda and it still failed emissions it suggests a possible fault with the catalytic converter (CAT). I would expect a possible CO fail on emissions, but with a fail on HC as well if this was the case. Don't know why it has a power loss unless the CAT is blocked. I assume you don't have any warning lights on when you loose power?
Mike

no warning lights or engine light no codes, did have but it said was the air flow so changed that still doing it but now no codes on reader

it can do it when its cold or hot on a short run or longish run. inbetween doing it it runs fine but i do think it has lost some pulling power.

Hi Gents
my code reader doesnt give any faults.
is there any way of testing the cats theres one on the manifold and one underneath..

Many Many Thanks for your help Gents

Mark

+1 on cat or possibly the rear exhaust silencer collapsed internally
also crank sensor failure = no code given

Hi,
I don't know of a way of testing the CAT other than during emissions, a pass Hydrocarbon result even with a failed Lambda and CO fail usually indicates the CAT is working, but it's still no guarantee.
I have seen reports on here that the first manifold CAT starts to disintegrate and the particles block the second exhaust CAT, usually resulting in power loss and the inability to rev the engine. It was also indicated that the Jimny will pass emissions with the manifold CAT removed, but I can't confirm this.
I guess you could remove the second CAT and see if any debris falls out. Depending upon circumstances it may even be possible to run without the exhaust CAT temporarily to see it anything improves, same with the rear silencer.
Exhaust CATs are about £70 on eBay etc and I've not read anything that would stop me fitting one. Infact my current one is aftermarket (paid more from exhaust place) and it's the same as eBay offerings, it's lasting well and passes emissions.

If you know someone local with a Jimny I wonder if you could compare exhaust "blow" to see if yours is less? May not be perceivable difference as it tends to build and restrict at higher RPM. Difficult to be 100% sure, sorry.
Mike

I,ve got a full system coming from scotland, i'll let you know what the outcome is when the full system is changed, both cats and silencer....

there was no difference when new exhaust was fitted including both cats and silencer box, a friend rang me and said get the coil packs replaced, so ordered the pair off ebay for £38 and its fixed no limp mode problems and pulling a lot better up hills etc etc ,,,well happy:) i've been on several runs now 100k + and running like a dream

Thanks for the feedback, it's always good to know the results so we can help others. Sorry it did not turn out to be the Cat, but it's always guess work if the ECU won't throw out a fault code. Pleased it's all sorted and you.

Mike