280 stroker tuning

Hello folks,
Recently purchased a 1998 xj. The motor (according to PO) is a 91 block bored 30 over and stroked. Runs dependably, but seems to lack a little power for what it is. Accelaration doesnt seem quite as smooth as it should be. Also, sometimes on startup, it will fire right up....other times, it take 4 or 5 revolutions and then "slowly" catches. It looks to me like everything is still stock under the hood (aside from that green motor block, lol.) My questions are:

1. Should i take this somewhere and get some adjustments made to the computer?
2. Can the stock computer be adjusted enough to handle the stroker and its requirements?
3. What would you recommend as a good running setup/program to ensure a long life from this motor with dependability and good performance?
4. Am i having air/fuel mixture problems with a stock computer?

I am very new to the xj...if one of my questions is a no brainer...flame me real good and teach me a lesson .
thanks in advance!
Hex

Little more info please?

What trans, axle gears, and tire size?

No matter what engine, if it has stock gears and 35"s, it's going to be a dog. On the other hand, if it's eared to match the tires etc, there may be a problem.

Trans, axels are stock. Tires are 31's.

I *think* the HO motors needed alittle mod to the MAP. I'm very new to the concept of stroking, and I'm planning out a 4.6 build. I believe I read on a site that the voltage needs to be modified to take full advantage.

Please forgive me if I am totally off base on this.

You will either need a Map adjuster of some sort (apexi, ftc1, home made, etc) and/or larger injectors. Also, make sure that your distributor is indexed correctly.

Thanks guys, i'll start looking into those.

Try to figure out what injectors you have(take pics and post if you don't know, get serial #). Follow Talyn's advice and get a wideband o2 to dial the WOT(wide open throttle) to 12.5-12.8:1afr for best power. Take a look at your spark plugs too. Oh yeah, here's my plate:

280XJ was against "the rules"(even though it was available)and forced me to put a number(not a letter!) after(so basically my 5th choice).

I'll see if i cant get some pics of injectors up this weekend. While working on the jeep, im trying to get a headgasket changed on a surplus 01 pt cruiser also. <--- what a peice of crap! So in addition to the map adjuster, ill need a new o2 sensor also? Awesome tag

Pics won't help on the injectors. Get the number off of it.

Alright, heres what i could get from the numbers on the injectors:
A N135 17121068
any suggestions?
17121068 - 20.85psi - 219.1 - HighVette v8-5.7l
am i good to stay with these?

Also, whats a good way to get the distributor indexing right?

Crank the engine over to 14 degrees BTDC on the compression stroke. Pull the distributor cap. The rotor should be pointing at the #1 cylinder contact.

Did they ever change the fuel injectors? Port the head? If the engine is stroked, then it usually requires larger injectors. The stock 4.0 comes with 19lb injectors, a stroked 4.7 needs something around the 23lb range. When you start up the XJ when it is cold, do you hear an audible "ticking" sound? You will have to step outside to hear it. What sometimes happens is when the engine is rebuilt and the exhaust and intake manifold is installed, the person with the new build forgets to re-torque the header and intake bolts. The gasket between the two at first leaks, then eventually burns out. Thus causing a hole. This is mostly noticeable when the engine is cold, but disappears when the engine warms up.

Other than this, you can try adding some "Seafoam" to your gas to clean out the fuel system (injectors, throttle body (TB), etc.). Sometimes just too much city driving causes excess carbon buildup in the system.

I have had these same problems and they are rather common.

Go with the easiest solution first---try the Seafoam or other injector cleaner to the gas.

Let us know how it goes.

KJ