bdcontraplayr

Hey guys,

So I'm not sure what else I can possibly do to my Laredo, so this is a finally Hail Mary before I sell it to a pick-n-pull.

For a while my XJ was giving me trouble off and on with a stalling/no start issue and now has gotten worse that I'm afraid to drive it down the street. Its a very inconsistent(frequency wise) issue I have been pumping money into to try and solve it. Whenever them XJ is warm, the idle becomes rough with a inconsistent popping/miss like feeling. And when it get warm, it's impossible to accelerate for a dead stop with out it choking till it stalls out. After it stalls, I have to wait anywhere between 5-30mins before it will start again. Sometimes I get lucky and it'll start and work fine a right away and I do not have to push to the side of the road to wait. But its inconsistent and comes here and there with days in between.

Here's what I have done to try and fix the problem:
New coil
New distributer
New plug wires
New plugs
New MAP sensor
New coolant temp sensor
New temp sending unit
New EGR valve and electrical unit
New/fixed vacuum lines
New fuel filter
New IAC
New TPS
New CPS
Cleaned the crap of of the throttle body
Seafoam treatment the engine, oil, and fuel
New air filter
And cleaned and made sure all contacts are made on that mass electrical connect on the driver side


I'm not a hot shot car wiz, I just love my XJ and I don't want to loss it. I'm just running low on funds.

I'm heading to bed now and will check this in the morning. I can give more info then.

Thanks.

Fred/N0AZZ

I would take it to a Jeep dealer and have them tell me "Exactly" what is causing the problem. Or a shop that is familiar with Jeeps like yours and either have them fix it or you can when you find out what it is.

I found out many years ago to know for sure what's wrong before you start throwing parts at it hoping you might get the right one down the line. Hell I'm too poor to do it that way, I take it and find out a lot cheaper in the long run.

Kingfisher

Yeah, Do what you should have done in the first place!

cruiser54

I would rent/borrow a fuel pressure gauge and check yours.

31 PSI at idle, rising to 39 PSI when the vacuum hose is removed from the fuel pressure regulator.

You may have a fuel pump on it's way out, which is aggravated by heating up .

bdcontraplayr

Yeah, I know I should have done this. I was just thinking it was going to be an easy fix since when I looked online it seemed like everyone else solved it with these sensor fixes and a tune up

bdcontraplayr

I'm going to do that this morning

bdcontraplayr

OK, so the Fuel pressure is at 31psi when in idle and 38\39 psi when I take off that vacuum line

knever3

So run it until it starts to run bad and your should see the fuel pressure drop off. It could also be the ballast resistor for the fuel pump. I have seen a ballast resistor fail on Grand Prix's that do the same thing.

bdcontraplayr

Ran it till it stalled, pressure was still the same. When it wouldn't start the pressure was at 37 psi.I was reading about the ballast resistor and a way to bypass it, might need to try this

knever3

I didn't see that you replaced the MAT sensor, or Manifold Air Temperature sensor. It's installed the the intake just behind and to the right of the throttle body. Here's what it can do if gone bad:

Basically - this sensor functions by providing a resistance-to-ground circuit that the computer (ECU) uses to determine how much fuel the engine requires. (The hotter the coolant - the lower the resistance.) The resistance of the sensor is read by the ECU which in turn adjusts the air/fuel ratio as close to 14.7:1 as possible. When a coolant temperature sensor fails (open circuit / no continuity) the high / infinite resisitance will cause the ECU to falsely read the max low temperature of -40 degrees F. The ECU then tells the injectors to enrichen the fuel mixture because it thinks the temp is really cold when it really isn't. A short to ground would cause a 'no-resistance' fault causing the ECU to think the coolant air temperature was extremely hot and lean out the fuel mix.

Read about it here:

http://www.lunghd.com/Tech_Articles/...iagnostics.htm

If the engine warms up and the sensor is shorted or open your engine will either dump a ton of fuel in and stall or lean out a ton. It will not return to the proper resistance until the time you say to start again. It's like a flooded engine kinda.

cruiser54

Ok, so maybe not fuel.

Click on the link in my signature below and do tips 1 through 5. Free and easy.

If you can solder, I would to 27 rather than 2.

bdcontraplayr

You know I was thinking of changing that. Might just go ahead and do it

cruiser54

NO!!!

Quit changing things!!!

IAT/MAT will not cause your issue.

Do the tips shown in my previous post BEFORE changing any other testable part.

knever3

I didn't expect him to just change it, the link shows what resistance it should test at.

cruiser54

Not YOU. HIM!!