xjcherokee90

Have a 90 model xj 4.0 auto. I have replaced tps sensor idel air, o2 and map. Still having the same problem. Driving and when I let off the gas it acts like it wants to die and other times it's fine. But when I hit the brakes to slow down or stop it will die unless I keep one foot on gas. Any ideas where to start will help a lot. Possible vac leak or what? Love my jeep but can't enjoy driving it because of this

carstock

mine has a similar problem. its a 98 4.0 with lpg conversion runs lumpy as hell on petrol and on lpg runs nice until stopping and the idle just drops to zero.
ive changed HT leads and put new Iridium spark plugs no change, there is also a brown wire wraped around one of the HT leads so put it back on. any ideas????

xjcherokee90

Sorry to hear you have the same problem just glad I'm not the only one though

carstock

just hope someone else has had it and knows what it is. frustrating and embarrassing when i cuts out at the lights

freegdr

did you adjust tps ?

freegdr

have codes read step 1...

carstock

??? no codes. what is step 1.

cruiser54

Start by cleaning the throttle body and IAC thoroughly.
Did you adjust your TPS? It's absolutely necessary to do so.

Ever cleaned your sensor grounds?

xjcherokee90

No codes and I have cleaned everything and replaced all sensors. And took it to dodge dealer to have tps set correct

cruiser54

You don't have codes anyway. The guy with the 98 does though.

Read this and see if you think it may apply.

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

xjcherokee90

Has all been checked before. Had trans out and cleaned all connections and found new places for all grounds

cruiser54

Ever done this?

Cruiser’s Renix Sensor Ground Test
Set your meter to measure Ohms. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.

carstock

took air intake off to access throttle boddy and tps the hole throttle body inside is coated with carbon so removing to give a good clean down,

xjcherokee90

Few guys from pirate 4x4 is having the same problem. There has been several claim the cps could be the problem, either dirty bad connection or could be going bad. $25 for a new one I think I may try it