I have an 89 xj 4.0 180000 miles bought for 300 had damage to the passenger fender and headlight headet panel
Problems
1) it cranks for about 10 seconds before it starts
2) it has a rough idle it will idle fine then about every 3 seconds drop 200 rpms
3) when the jeep goes to upshift at around 40 mph it jerks really bad till I hit about 48
4) I can spin the front driveshaft easily with no resistance or grinding in 2h with the wheels on the ground
Please help o and everthing is bone stock has new plugs and the temp sensor is relocated to airbox

 

1) try turning the key to "on". Wait 5 seconds. Turn it back off. Now start engine. See if that helps. (fuel system may be losing pressure..bad check valve).

2) 3) This could be so many things.. esp. with a Jeep you don't have a history with. I'd start with the free stuff. Clean up your grounds and battery connections. Clean up all sensor connectors. Check your plugs, wires, cap, rotor, replace as necessary. Check fuel pressure, see if it's low or unstable. Check vacuum lines, esp. the one to the MAP sensor.

 

+1 to all of Radi's suggestions. I'm sure Cruiser or Flintstone will be along to post directions for ground refreshing or you can search this forum using those key words. There's also a great write-up for testing and adjusting virtually all Renix sensors, I don't have the link handy but someone will.

 

Start by refreshing all of your grounds! The Renix does not like marginal ground connections. As the previous comments have suggested, start with the free stuff. I would also add a ground from the negative battery to the radiator support. With some tlc, the renix will be a fantastic running machine. Just tell her that she looks good in that dress and that she's not fat. The renix can get upset if you say the wrong thing to her.

 

Good advice so far. These will help. Free and easy.

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals, and adding dielectric grease before plugging it back together. Be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.
ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then dielectric grease should be added before plugging them back in. I do this on every Renix era Jeep I purchase or work on for someone else.
Revised 03/15/2012

 

This is why I love this forum everyone is so nice and eager to help I am absolutely in love with xjs this is my second one but I'm only 18 so not real experience with them but I do have one advantage I work at napa auto parts so with the grounding could that really be all my issues? It seems so simple and I'm definately going to get some electrical cleaner some dielectric grease and some purple power and clean all my terminals and connections and completely clean my throttle body

 

As for #4 that may be normal if you have a vacume disconnect front axle. If you do be sure to check that it's working correctly

 

Start with the ground refreshing. Don't skip any steps. It's super important. In the write-up, note how many very important things rely on good grounds.Since you work at Napa, buy those cables noted in the write-up at your employee cost. Buy a multimeter while you're at it. You'll need it. Let us know when you've done the ground refreshing and other stuff I've posted for you and we'll give you another homework assignment.

And BTW, you're right that this is the best forum.

 

Will do ill keep everyone posted and as for turning my key on for 5 seconds then starting it it makes no change and how do I know if I have a vaccum disconnect front axle

 

http://www.jpmagazine.com/techarticl...ect/index.html

 

On the backside of the front axle on the passenger side there will be a vacuum shift motor mounted there with 4 bolts and 3 vacuum lines going to it.

Do the grounds including adding the cables noted and then we'll address your crank times. Renix requires a few seconds even with everything perfect.

 

Should I see any significant gains from the cleaning of the connectors and cables and grounds

 

You could. Do them and report back. We've got more for you after you've completed those given you.

 

all I have done so far was clean the grounds behind the dipstick tube and the cable on firewall and wow the rough idle is almost gone already!!! Thank you all

 

Get to work and finish it.