Timing on 98 tj?

kcub · #1 (**permalink**) 10-23-2009, 06:48 PM

What should the timing be at idle on a 98 tj 4.0L. I have a timing light and want to check the advance. Still chasing down the miss at 1500 rpm.

Bounty__Hunter · #2 (**permalink**) 10-25-2009, 09:32 PM

It's not adjustable on the TJ, and doubt it has timing marks because of it.

SteelHeadz · #3 (**permalink**) 10-26-2009, 06:47 AM

That's correct .All 2.5L 4-cylinder and 4.0L-6 cylinder engines are equipped with a camshaft driven mechanical distributor containing a shaft driven distributor rotor. These distributors are equipped with an internal camshaft position (fuel sync) sensor . This sensor provides fuel injection synchronization and cylinder identification.
The distributors on 2.5L or 4.0L engines do not have built in centrifugal or vacuum assisted advance. Base ignition timing and all timing advance is controlled by the powertrain control module (PCM) Because ignition timing is controlled by the PCM, base ignition timing is not adjustable on any of these engines.
The distributor is locked in place by a fork with a slot located on the distributor housing base. The distributor hold-down clamp bolt passes through this slot when installed. Because the distributor position is locked when installed, its rotational position can not be changed. Do not attempt to modify the distributor housing to get distributor rotation. Distributor position will have no effect on ignition timing. The position of the distributor will determine fuel synchronization only.
All distributors contain an internal oil seal that prevents oil from entering the distributor housing. The seal is not serviceable.

kcub · #4 (**permalink**) 10-26-2009, 07:12 AM

Thanks guys. This ended up being my problem with the missing off idle. The same distributer fits the 4 and 6 cyl. engines. You have to line up a hole in the sync ring with a hole in the dist. housing to set which engine you are using it for. I didnt use a pin to hold the ring in place and miss-allined the dist. Close enough to run but not close enough when you gave it gas. Thats what i get being in a hurry. Payed my stupid tax of two weeks of head scratching. Runs great now. thanks for the replies, the info was useful and appreciated. Now on to the next item to fix.

Bounty__Hunter · #5 (**permalink**) 10-26-2009, 10:32 AM

The alignment pin is an easy requirement to miss, I got lucky and used the FSM during installation or I would have missed it also.