Hi.. Im driving 98 XJ Manual..
The car was so powerfull compare to other xj's.. It used to burn out in first and second gear
But suddenly it looses power it feels like u added tons on it..
I changed fuel pump, spark plugs, new injectors, wiring, distributor and cleand the throttle body but the car still the same.. The car was so fast it takes seconds to reach 160km/h
But now I dont think it gonna reach 160
Please help me
I6 engine with stage 2 clutch and 99+ intake

 

Check engine light on?
vacuum leak, Map sensor, oxygen sensor, plugged catalytic converter, plugged fuel filter, bad compression are some possibilities to look into.

 

No o2 sensors and no catalitic converter for almost a year and the car is running perfect
I was racing with my friend and the car was perfect I turned it off and after 15 I started the car everything was good but when I hit the pedal it takes more time to reach 5000 rpm pefore the car was so fast since I bought it everyone keep on saying that its stroker cus of its power but now its even worse than a normal XJ
I changed everything and still the same
And my car has no fuel filter

 

breaking forum rules. Needs a cat. O2 sensors make a huge difference. Otherwise it's running off of guesses and it could be running Rich or lean but it needs the o2 sensor info to preform at its best.

 

You realize of course that prior to 1992 all export Cherokees were NOT equipped with catalytic converters don't you? The European Union didn't enact Euro 4 emissions standards till 1995 so pre 1995 export automobiles don't have Catalytic converters on them. With the OP's nickname it is highly possible his cherokee doesn't by law have to have one. Just saying' I also see his is a 1999 so Catalytic it needs.

 

I understand that I need cat and o2 but what I dont understand is why after a year the start to run slow I reprogramming the ecu with superchip and full exhaust system and 99+ intake and stage 2 performance cluch all that and when I race with other xj's its like im driving a Honda compare to BMW v6
Just in 15 mins the car looses all its power its very hard now to reach 160kmh
Before I reach 160 in 1km
Now it take arround 2.5km to reach 160kmh

 

Hell mine won't run 80mph/128kph without sounding like it's coming apart.

 

The O2 sensor is probably the most important senor in the EFI system. You may want to read up on the fundamentals.

 

I dont think so bro.. Cause for almost a year im driving the car and its the first time to do that..
I removed the o2 sensors long long time ago

 

^
You're the engineer, carry on.

 

Well since the o2 sensors help control the fuel output, yes they are very important. Without them you will wash your cylinders after enough time running rich, causing low compression, and therefore possibly causing a poor running condition.

How long have you been a mechanic?
I ask this because if you think that o2 sensors don't mean anything to an efi system, you should hang up your wrenches.

Next thing I want to point out..... why the hell did you post this in the electronics section? You can't even forum bro.

 

I know that the o2 are very important but here in dubai the parts are very rare.. I post it here is becuse its my first time to use this app and I dont know where should I post sorry

 

Thats why ppl here they disconnect the o2 sensors

 

Then why did you say they are not important?

 

I didnt say they are not important.. I said I drove the car almost a year without o2 sensors and its working fine.. Second thing I said the car become like a cow in 15 min it was OK turn of then back on and till now still the car work like a cow
The superchip gave me 6000rpm but in 3rd, 4th and 5TH gear it wont hit 5500 max is 5100rpm no cut-off while driving only if I stopped and riv it will hit 6000