I hope the sensor change takes care of it for ya, but I'd be willing to bet the problem will still be there.

1913

I hope so too i just received my spare parts xj. so i am going to try the new one tomorrow. And keep you updated.

So an update! The sensor did not make anything! My tuner told me that it is not electrical or vacuum lines leak. I am disappointed i don't know where else to look!

one thing i noticed but i think its ok is that after installing a faster water pump and a 3 row cooler my electric fun does not start at all but the temp gauge is all the time at the first quarter! Might that be the problem?

Your looking for a mechanical issue when there isn't any.

I'll tell you again... It is a fuel map related issue (not map sensor). I can't tell you how many times I've seen a bouncing idle.

Your noticing it change when it get's hot simply because the engine will be using a different cell value than when it's cold.

Compressor Surge, No bypass valve used, Extreme Examples...

https://www.youtube.com/watch?v=LziDXhy2fxs

https://www.youtube.com/watch?v=9mQIG-e1how

Sound familiar??

Try pulling the vacuum hose off the Fuel Pressure Regulator and cap the hose, and see.

With the compressor surging, the intake is seeing fluctuating vacuum, up and down, and in turn the FPR is seeing fluctuating vacuum and fuel pressure is going up and down and 'richening/leaning' the mixture.

I have plugged to my laptop the AEM, the fuel map is normal.

I think that the problem is that. I will try to put the vacuum line before the sc and see what will happen!
I can not find find a by pass valve for my sc in greece!

I these two cases there is a response to the throttle in my case there is no response to my throttle. I cuts off fuel! Although the sc tries to increase RPM the engine is like draining from fuel.

IDK, This is the problem with a "Momentum Motorsports" Jeep SC Kit.

You need a bypass valve.
You need proper fueling.
You need boost timing retard.
You need a 'Tune', not just bigger injectors.
You need intercooling.
In short, you need a complete kit and not just a mounting plate and piping.

I have a vacuum leak on the evaporator canister. Would that be a problem?

I will not disagree! But j am from Greece and i love my xj so how can i do all of them while nobody in greece knows how to tune an xj. Evermore to supercharge an xj? I am doing my best to make my girl happy strong and beautifull although i do not have the means to do it.
If i were in the States believe me i would be on your list 5 years ago! I think that is when i first saw your site.

I tried to find a way to buy your ki but with the taxes and customs i would have paid more than 12.000 $ to get it. The point is that i am trying to make an xj for what i want it to be. Experimenting and doing my best, for the spare time i have.

The vacuum leak can cause the idle surging, but usually leaks cause a fast idle.


I feel your frustration.


If you barely crack the throttle does it still surge or does it smooth out?
Only when hot, it does it?

It idles fast cold and hot but it smooths out
When is hot is bouncing!
I have found some other staff that are installed incorrectly the vacuum hose that goes to the fuel pressure stabilizer is on the manifold and takes both pressure and vacuum, so i have to change all the vacuum lines and put them before the SC.
I will leave only the MAP and AEM vacuum lines on the intake manifold.

I am trying really hard to figure this out but there is no free time as i am working everyday 12-14 hours. even on weekends.

I have just changed all the vacuum lines i have just found out that the Intake Air Temperature sensor is dead! :-(