Help, Fuel or Ignition!!!

Ok, I am calling on you guys help once more. My Jeep is
seriously making me mad. It is a 1990, with the 4.0 and auto. I was on my way up to run the
pipeline trail north of Phoenix, Arizona when my Jeep was running perfectly fine then started lurching, just exactly as if it were missing. I was getting on the 17 and was on the on ramp from the 101 and it stalled out all
together. I coasted off the ramp onto the side of the freeway and tried starting it several times and all it would do was putter at a very low rpm for a couple seconds and then totally stall out, probabaly like 100 - maybe 200
rpm... (i have no tach). It happened like 15 or so times... Then I
let it cool from the normal temp of 210 degrees and it got down to around about 180 degrees and then it did its putter thing for about 2 - 3 seconds and then jumped imedietly up to its idle speed and so I turned around and came home. It didn't bother me again all the way home... Also at different times if I let it sit there and idle it will start to putter and if i give it any gas or "bleep" the throttle it will stall out. It only started doing this about a week ago. I changed the fuel filter about a week and a half ago so it's not that... I also put plugs, wires, a cap and rotor on about 5,000 miles ago so it couldn't be that. I am at a total loss! PLEASE HELP!!

Tom

When was the crankshaft position sensor (CPS) last changed?

It was changed about 4-6 months ago.

Tom

fuel pumps can give a lot of different problems. when was it last changes? checking the fuel pressure would be a good idea.

if you put an aftermarket cps on, i would change it and get a factory one.

Yeah as soon as I can get my hands on the guage I will do that, but as far as I can tell it is the original pump and I have 161,500 miles. I never thought that being electric, it would flucuate like that though.

Tom

Yeah it does have factory CPS on it.

the egr valve could be sticking open

along with the electric control the pump itself is still mechanical. if all of your electrical values are right and you cave taken care of the ignition.the pump might be your problem.

tchase said:

along with the electric control the pump itself is still mechanical. if all of your electrical values are right and you cave taken care of the ignition.the pump might be your problem.

Click to expand...

?

I would put a fuel pressure guage on it first off........ sounds like a classic example of a fuel pump about to die.
Doesn't really sound like a cps problem to me...... my experience with bad cps's are normaly no start or intermittant no start or just plain dead but cranks with no sign of life at all.... if you don't have a crank signal it won't run.

Im juat wondering if the O2 sensor or the coil could cuase this to happen intermitenly (sp) like this.

Tom

This is one of those problems you could throw lots of parts at and still not fix. You may be money ahead to take the rig to a mechanic who understands Renix XJs and explain to him the problem. He will hook up the test set and check over all the sensors to see if things are in range.

I was thinking you need the throttle body cleaned, but it could be a sticky EGR. It could also be a worn throttle position sensor. Like I said you could throw lots of money at it.

This sounds like one you need some professional help. I hope you have a Renix knowledgeable mechanic you can take it to. I had a problem like this which had me ready to replace parts I had changed already. I took it in and he found it was the EGR, they had a new one in stock and it was installed that day. The labor was free since I paid for 1 hour to diagnose and included in that 1 hour of labor to install new parts.

You may be at the beginning of a sensor replacement program if you want to keep the XJ.

Where is the EGR valve at on this thing??? Is it something I can clean myself to see if it helps??

Tom

The EGR is low on the intake manifiold, facing the driver's-side fender, below the throttle body. If it dies it usually sticks open, allowing too much exhaust back into the engine, which stalls (or nearly stalls and runs rough) at low rpm. The test is to pull the vacuum line off the transducer (the black vacuum line coming from a solenoid (switch) on the driver's -side fender, around the airbox, to the flying-saucer like thing attached to the EGR). If the low idle/stall goes away, then you need a new EGR. My 1990 with 4.0 I-6 engine is on its third EGR. To change it, remove the airbox for access. The mounting bolts go into the aluminum intake manifold so take it real easy on tightening them up. Use a bit of antiseize on the exhaust tube coming from the exhaust downpipe, so the next change will be easy. 1990 is the last year to have an EGR vale. The HO engines do the same thing via valve timing.

Ok, I checked the fuel pressure and it doesn't seem to be changing at all. It does seem like the pressure drops fast if I shut the engine off. I was thinking I heard that was bad if it drops fast like that. also the only vaccum lines that I could get off were the ones on the switch on the driver side fender. The line on the switch closest the the cab seemed to have no vaccum at all and the one closest the the nose end did have vaccum but seemed to not change the idle...

Tom