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would you buy a '99 4.0 4x4 140k?

sometimes things are not too good to be true, example I scored a 89 xj 4.0 4x4 with only 128000 on the clock for $350 and the factory air still works no issues what so ever, best money I have ever spent. As far as the misfire it sounds like possibly injectors due to low idle and stalling, hook up a fuel pressure tester and see what your fuel pressure is, should be 338 ±14 kPa (49.2 ±5 psi) at idle and shold not fall below 30 psi for 5 minutes with pump off.
 
I do have a multimeter, not sure how 'good' it is got it about 15 yrs. Ago from Radioshack. Dug it up out of the garage last night. Today i'll do some seafoam and sensor testing.
 
Some analog meters do not work well for this kind of thing, but for free, it's worth checking. You might also plug the sensor back in, and try reading the voltages if it doesn't work well for resistance. The pinout and specs for testing most of the sensors are posted around here somewhere as well.
 
i would clear the codes and go drive it! then you can see which codes come back. i think you have multiple drivability problems. and i think you just cured one of them! mike

p.s. i believe you got a good deal! mike
 
Picked-up an inexpensive digital multimeter and some nice vinyl fabric 'for the headliner today.

Question- I noticed yesterday, when I fisished the tune-up, that the distributor isnt positioned like all the diagrams i've seen. Number 1 'distributer-cap' is at about 5-o'clock not 6-o'clock like the pictures show relative to viewing perpendicular to the engine. Does yours sit a 6-o'clock?

I dissmissed this yesterday but now i'm wondering if this is normal?
 
So I haven't even opened the new multimeter. Decided to use a little bit of seafoam in the gas and drive her around a bit to see if she was still missing. No misses around the neighborhood and check engine light went out. Got a little braver and went out to the service drive and got her up to 55mph and she started missing again. Ran around a little while longer just to run the seafoam through. Stopped and got a little more gas to dilute the foam. Left the gas station and the check engine came back on. Headed straight to autozone and had the codes checked again.

Only threw 1 code P1391 CMP sensor. Hope thats the culprit.
 
Unfortunately the cam sensor is inside the distributor and is not intended to be a serviceable part. Might check the wires and clean the connector with some CRC electronics cleaner from autozone (probably ought to do all of them judging by the pictures). Otherwise you might have to replace the distributor.
 
ehall said:
Unfortunately the cam sensor is inside the distributor and is not intended to be a serviceable part. Might check the wires and clean the connector with some CRC electronics cleaner from autozone (probably ought to do all of them judging by the pictures). Otherwise you might have to replace the distributor.
Click to expand...
Not so. Cam position sensor on a 99 is replaceable. ON earlier models (my experience with a 93) you had to take the distributor out and apart to replace it, but on later models (95 and up) it comes off the top. I did it on my 95. A five minute job.

But I would not replace that sensor unless you have reason to believe it's bad. A bad one will usually throw a code, and on the 93 and 95 it wouldn't start at all. (edit to add, I didn't see above where you say you got the code. Should read more carefully, shouldn't I?)

I second the suggestion to clear all the codes and run it again first. Sometimes a single fault will trip multiple codes. For example, if you have a bad cam sensor, and trick it into starting and running, it will then throw a false crank sensor code. (edit to add, may not be the case on a 99 if it starts without trickery).
 
A little late here as well, but even if it is a distributor that's not too bad. About $150 and easy to install.

Btw I love my '99. Picked her up for $750 with 157,000 on the clock in PRISTINE condition. Owner said she had a blown head gasket. My compression tests disagreed. Turned out to need a new water pump, and she's running like a champ 10k miles later. Third Jeep to me, about the 15th to go through my family. Once you get the hang of these vehicles, they really do become addicting.
 
gradon said:
If you still have a P1391 after the new parts, you're gonna have to index the cam sensor in the dizzy.
Click to expand...

What does that mean exactly? You might be on to something.

Going to test the CMP tomorrow before I replace.

Found a thread where the CMP was replaced and still threw P1391 code. Ended up being the Distributer.

How much play should the rotor have if I wiggle it?
 
So to be clear. Low idle, hesitating from stop, occasionaly dying at low RPM and shifting to N & P "not always". Misfiring above 50mph. Throwing code P1391.

Like I said I will test the "CMP-CPS-CKP" whatever it's called tomorrow based on this procedure I found:



TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C "2nd & 3rd terminal inside connector". Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.
 
DO THE FUEL FILTER!!!


Seriously, it seems like that was the original Wires and cap and such I'm SURE its the Original fuel filter and those things can make a HELL of a difference. Old Ford my grandpa had made the car not start even.


Its like a few bucks and maybe half an hour to change. If it were me, I'd do it first thing in the morning.


Defiantly blow through the old one to feel if its clogged. I would have got that in a heart beat.
 
DO THE FUEL FILTER!!!


Seriously, it seems like that was the original Wires and cap and such I'm SURE its the Original fuel filter and those things can make a HELL of a difference. Old Ford my grandpa had made the car not start even.


Its like a few bucks and maybe half an hour to change. If it were me, I'd do it first thing in the morning.


Defiantly blow through the old one to feel if its clogged. I would have got that in a heart beat.
 
collkid said:
DO THE FUEL FILTER!!!


Seriously, it seems like that was the original Wires and cap and such I'm SURE its the Original fuel filter and those things can make a HELL of a difference. Old Ford my grandpa had made the car not start even.


Its like a few bucks and maybe half an hour to change. If it were me, I'd do it first thing in the morning.


Defiantly blow through the old one to feel if its clogged. I would have got that in a heart beat.
Click to expand...

On a 1999, the fuel filter is part of the "fuel pump assembly", located inside of the gas tank. Not like the older models where it was easily accessed along the fuel rail.

It is generally not replaced preventively, but only when testing and symptoms point directly to it.

So while testing fuel pressure is never a bad idea with a gauge, replacing the fuel pump without some verification of failure isn't recommended.
 
Just tested the cpm. Not sure if im doing it correctly, not very good with electrical, but it looks like the cmp sensor is reading 45 ohms, is that considered low? Faulty? Anyone ever test theirs?

Test performed with engine off. No Key in or anything.
 
Last edited:
Got the cpm sensor off. Sure is a difficult litte bugger to get to. Cleaned it up with electronic cleaner. Tested again. Still at 45ohms. Heading to Napa to get a new one.

Please someone stop me if you know better! Don't have a $100 to waste.
 
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