Suzuki Jimny 2005 automatic powerless on highway

Hi I have a problem with my jimny 2005 automatic but can not find what the problem is. The car feels really nice in the engine and automatic transmission. But when you drive at higher speeds on a motorway for example and there is a slightly steeper road it loses speed and feels powerless. Is there anyone else with a  automatic Jimny who can share their opinions? Does not reach more than 100 km / h on the motorway and as soon as there is a little hill the speed is reduced to 70-80. The car is in very good condition otherwise with service done and I also changed the oil and filter in the gearbox. but it did'nt help. No codes. It have 96.000km. Please let me know your opinions guys its my first Jimny and i love it but i need to fix this problem. 

It's probably not the automatic gearbox unless the car has entered 'limp mode' if the Jimny has one?

Has it always been like this or has just started?

More likely it is air/fuel/ignition/exhaust which is causing the lack of performance.

Air - Check air filter & MAF sensor
Fuel - Correct fuel, check filter, O2 sensors
Ignition - Check plugs, coils (crack), timing
Exhaust - Is the exhaust or CAT blocked
Brakes binding?

As it won't rev it suggest air/fuel flow problems, I would start with the easy things, air filter, plugs and work you way round to the difficult things. The plug colour might tell you more about waht is going on.

As Lambert says does your code reader give you live values, that might help.

Unfortunately without any codes logged, it might be a case of working your way through the list. I am having a similar problem (not as severe as yours) with my other car (not a Jimny), it's just a case of checking everything, I have been through O2 sensors, coils and plugs, air filter, now it is looking like an over-reading MAF.

Maybe we should start with which Jimny, and what engine does it have?

Thank you and thanks for your information. I dont have the diagnostic to see live data from the transmission. I maybe should go to suzuki and let them search for the problem. It goes up to 4000rpm and no more then its stop with power and when its shifts to the last gear it looses more power in the 90km/h. The gearbox shifts smooth and nice. The airfilter is new, the exhaust and cat is new, spark plugs is new. The only thing i dont know about is the fuel filter. Its a Jimny 2005 vvt automatic i think its the M13A with 16v DOCH enginge. 

Thanks for the information. Yes its revs to 4000rpm and then its just stop and powerless. There isnt any slack in the throttle, i have controlled it and its okey. I will order one obd2 tool and download the program. I have also checked the map sensor and its no problem with that. I own the car for 2 months now and this is the only problem with it. The car is in very nice condition if we ignores this problem. It does the same if you drive on a smaller way and its a big uphill on 70km/h it loses power and goes down to 50km/h.

Hi they have checked the throttle and we replaced it but the problem is still going on i had it checked by two mechanics and they say they belive its the gearbox. I have now booked a time to checkup by suzuki. I hope that it isnt the gearbox beacause its very expensive here in sweden.

If it would be the gearbox it should get pretty hot after a short drive if it „eats“ all the power. I would think that you even can smell this.

So are you saying it will only rev to 4000 rpm with the vehicle stationary and in N?
If so its likely Dr Robin has mentioned the possible cause, me thinking blocked 1st or second CAT.
Do you know anyway to get a drive in another auto so you can compare?
The Jimnys can feel a little powerless if you come straight from a "normal" car, so just trying to eliminate the possibility that it's normal on your hills etc. It does sound faulty though.