[nameless]

1989 fully loaded limited xj

4.0L


idles alright, go to drive it, throw it in gear, drive about 20 feet, motor just throws to like 200 rpms and they stay down, i'll play with the gas and it seems like it wont go over 500 rpms


then after maybe 30 seconds it will drive again for about another 20 feet


i hate these stupid renix motors hah

[robdoggydog1]

test fuel preasure with a guage sounds like a good place to start , i think yours has a ceramic resistor type of thing on the drivers side fender this regulates fuel pump presure or something to do with fuel pump,you can jump a wire across to test for now, also if that checks out try disconnecting your egr and plug the vaccum line to test.

[tjwalker]

1. Test fuel pressure at the schrader valve on the fuel rail WITH A GAUGE. Your target is 31 psi at idle.

2. Test AND adjust your throttle position sensor. Yours IS adjustable.

[BrunoS]

lack of power is a fuel related issue.

check and replace:

1) $12 fuel filter in the back area. good thing do to every 30-50k miles on vehicles where it's accesible. on yours, it may even be the original!

2) broken/cracked vaccum hose or brake power booster check valve is leaking. how to check? pump brakes a few times after parking overnite. you should have a few pumps of power boost if the check valve is holding. if pedal is firm on first attempt to push...your $10 check valve on the booster going to intake manifold is shot.

3) rare one here...but check air filter if much of your driving is on dusty dirt roads. a plugged filter can cause same issue.

4) as far as tps...try unplugging it and drive it. it will work, but mpg will hurt until you replace it.

5) are all plugs firing? any really rough idling/missing? if so, pull and replace all spark plugs.

6) check oil level to see if it's too low.

7) battery old/shot> alternator is pulling every amp it can to try and charge dead battery, check voltage. should be 12 volts motor off, 14 or so idling, and no less than around 10 volts during cranking to start.

8) last option...fuel pump may be on it's way out. check pressure at fuel rail with gauge AFTER changing fuel filter. should be close to 40-50 psi if all is well, when motor is running. you need pressure and volume for the injectors to do their job. listen for a "click" at each injector when motor is running using a piece of fuel line hose or such, touching each injector during the process. or, use a fingertip to feel each click. one that's missing has other issues.