engine troubles

on an 1989 xj 4.0 4x4 is there a way to check if the knock sensor is bad or is there a way to by pass the sensor temperarly so that i'm not throwing parts at this

Describe your symptoms.

very rough idle sounds like it is missing somthin bad and it won't go over idle.

Is there visual evidence of damage to the sensor? A bad knock sensor "can" retard timing intermittently if my memory serves me correctly, but from your description, the problem could be about a dozen things. The fact that it doesn't go over idle makes it sound like something other than the knock sensor IMHO.

I would start by checking fuel pressure at the schrader valve on the fuel rail. Takes just a few minutes with a fuel pressure gauge. Compare your reading to factory spec. You may have a fuel delivery problem. Testing and adjusting the throttle position sensor would also be a good idea.

This is a process of elimination and you need to start with the absolute basics in your situation. Also, what is the status of tuneup hardware? Meaning plugs/wires/distributor cap/ rotor/air filter. Don't want to be chasing your tail when it's something simple.

all tune up hardware is brand new

rebelcherokee said:

on an 1989 xj 4.0 4x4 is there a way to check if the knock sensor is bad or is there a way to by pass the sensor temperarly so that i'm not throwing parts at this

Click to expand...

Just unplug it and try it. I don't use mine, don't need it on most 4.0s.

Doesn't sound like knock sensor. What about firing order of wires on cap?

winterbeater said:

Doesn't sound like knock sensor. What about firing order of wires on cap?

Click to expand...

x2,

or the vacuum line to the map sensor got knocked off.

I got the knock sensor fixed it didnt help, I put my timming light on each plug wire and found the #1 and #6 are not firing but 2,3,4,5 are firing. Does any body know what would cause this problem?

Too much resistance in the wires? have you checked the wires, by gorund the end, to see if you get spark?

YOU GOT TWO POSTS GOING ON THIS????????????

rebelcherokee said:

all tune up hardware is brand new

Click to expand...

did that include new spark plug wires?

are the plug wires making good contact on the cap and to the plugs?

did you have this problem before the tune-up?


here is some info i got from the "4.0 liter multi-port fuel injection" manual i down loaded. dont know where i downloaded it from but i know you can find it on WWW.lunghd.com

i would test/inspect/clean the cps and the sync signal generator in the distributer(i believe its also called the startor) because its 1 and 6 not firing. the cps uses notches(3 of them) on the flywheel as reference points. the cps uses the same notch for cylinder 1 and 6 as a reference point, if it doesnt see this notch it wont send a signal to fire. if not the cps, its most likely the sync signal generator in the distributer. if this doesnt work proporly, then it wont send a signal to either 1 or 6, 2 or 5, 3 or 4.

how do i sync the signal generator

rebelcherokee said:

how do i sync the signal generator

Click to expand...

you need to test the sync signal generator.

you should download a fsm or the manual i referenced in my other post. or go here for the testing of it.

http://www.lunghd.com/Tech_Articles/Engine/Cam_Position_Sensor_and_Sync_Pulse_Stator.htm