Cherokee wont idle/ dying/ tried lots of things

this is my first post on any jeep forum, so please let me know nicely if I posted in the wrong place or anything. I have a 97 cherokee country with 144,000 miles. Bought it stock, put a lot on it. Since the day I bought it, when I start it up, after about 10 seconds of driving, it will make a popping noise under hood, Its very predictable, has always done it. only does it for about 5 seconds. Dont think it has to do with my problem. New alternator, battery, starter, plugs, wires, cap, rotor, o2 sensor, air filter, lots of little stuff. put in 4:88 gears do to 35s about a month ago. Then put in dodge neon injectors. Put about 400 miles with those injectors. had about a quarter tank, Got off the highway, and as I was coming to about 10 mph, it started idling at about 200 rpms, then died. Took it home with two feet on pedals, Changed out the Idle control valve, Cleaned the body, Changed map sensor, Throttle position sensor, o2 sensor, cleaned dist. cap, checked for spark, Voltage is good, Never had a ground problem, so didnt bother, new CPS, (which actually caused a new problem- missing even worse at giving steady gas driving down the road). Havent checked pressure on fuel rail due to not having the tool. I have yet to figure out the exact characters of it. Ill start it up cold, it runs fine. I get in it, drive about 100 ft, come to a stop, then it dies. Takes about 2 minutes of sitting to start back up. Then runs like 1920s washer machine unless I can get it over 2000rpms. Jeep hasnt thrown any codes except downstream 02, but thats because I have no cat, so no sensor. Dont know what else it can be. It is my daily driver, please help.

Come on guys, help this young man out. I told my son to post this and the great guys from naxja would help him solve his mystery. Please don't disappoint him.

have you hooked it to an obdII scan?

The popping dose not sound normal.. and could be the cause of this problem.

Start with checking all your relays and fuses on the passenger side inner fender for broken/worn out fuses/relays

I appreciate the help. But yes, used obd tester, no codes. Besides 12, because I disconnected my battery for a few. And when it does that popping, it's just backfiring, and bucking. It's always predictable. Does it every time I start it up and take off. Always done it. Haven't checked my fuses or relays yet, but I will today.

Got me, I'm trying to think of something that would cause this and not throw code. Just thinking out loud, but if a single cylinder has a vacuum leak, it shows the O2 sensor too much oxygen. The PCM only has two choices cut down on oxygen (air) and the only way it has to do this is to close the IAC. A single cylinder air leak isn't going to idle you up much, the IAC controls air to all the cylinders at idle. It can also richen the mix some, add fuel, but it will try to keep the idle down to acceptable levels. I call them computer conundrums, a problem the programming has no answer for.

I'd likely start with the basics and do a compression test. A leaky intake valve might be involved. Re torque the intake/exhaust bolts, but be really leery of the end studs they break off easy.

Find TDC I and check the rotor position to make sure you aren't one tooth off.

Then I'd check the voltage at the sync sensor and do a volt meter sync sensor test. Some partial shorts to ground can screw up the 5 volt feed voltage to the CPS and the sync sensor and never throw a code. I've never had to time a sync sensor so I sure can't tell you how to do this. While you are in there, gently push the rotor shaft to the side and gently lift it, excess play is a cause for concern. The bushing wears and the thrust washer wears, could be one or the other is worn out. Not likely to be your problem, just something to check.

I'd also disconnect and plug the purge line from the purge solenoid to the intake, just for a test. I usually make a set of short pieces of appropriate size tubing with a screw in the end and plug off most all of the vacuum lines into the intake. One of my first checks for an idle issue. Takes less than half an hour. I keep the tubing set in my emergency (in Jeep) tool box.

Just some ideas, no real solutions. If it were easy it would already be fixed, .

You always have to check the front (and rear) O2 sensor wires and the CPS wires to make sure they aren't cooking on the exhaust.

That rear O2 sensor is more important than you think, it makes sure the CAT has enough O2 for a successful catalytic reaction. It is actually the baseline for whatever the front O2 sensor (PCM) decides to do with motor management. You are unlikely to ever have a good fuel air ratio without it.

Thank you for your response, that's a lot of good information. I checked for vaccum leaks, all that I saw are good. I'm gonna recheck and look up every vaccum and check for leaks on all of them. It has always run a little rich because of no cat and rear sensor, but lately it has been running really rich. Strong smell. I didn't think it could be my distributor. I thought it could maybe be a fuel pump? I used to run it on the gas light all the time before I had a lot of money. Every turn, it would cut out, because of slosh in the tank. I'm thinking maybe it's come back on me and the fuel pump is going out? When I turn the key, I hear the pump engage for about 2 seconds.

OHM your TPS ground. Ohm your block to firewall ground. An iffy ground can cause all sorts of grief. I just cured a rough idle (on my 96) by cleaning the block to firewall ground. I sure don't know why the ground made a rough idle, but it was rough before the ground cleaning and the idle was smooth afterwards.

Switch your meter over to the AC scale, make some volt tests and see what you get. Test someplace away from the battery. What is the DC volt reading at your battery with the motor running?

I've got an idea rolling around in my head, all of your issues can be explained by a bad diode in the alternator. You can sometimes pick up an indication using the AC scale on your meter for a test, depends on the meter and engine RPM. The battery acts like a big condenser and suppresses AC current. Computers don't like AC current or pulses, it tends to scramble the data.

8Mud said:

I've got an idea rolling around in my head, all of your issues can be explained by a bad diode in the alternator. You can sometimes pick up an indication using the AC scale on your meter for a test, depends on the meter and engine RPM. The battery acts like a big condenser and suppresses AC current. Computers don't like AC current or pulses, it tends to scramble the data.

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Well, bought a used Suzuki dual-sport back in the 70s, ran like cr*p, come to find out someone had removed the rectifier and it was running on A/C.

Definitely worth a look.

I will definitely recheck my grounds after work. Debating on doubling up the big three with a spare harness I have in my garage. With new battery on, idling at 700 rpms (when normal) and with my 32,000 lumens of lights and electric fan and ac off, voltage is at 14 volts. As for the alternator, I'll try and test it, I wasn't the on who bought it, owner before me did. But I'm guessing it has about 15,000 miles on it. You can see, it's very clean. Compared to everything else. But I've never had problems with my battery until 2 days ago. I don't know if messing with this, then starting it, messin with that, starting it, just expiereminting with it killed it, or just after a while running all the lights and junk I've got wired up, eventually wore out on me. But I'll see about the alternator, do some testing. It could be bad.

Double check your 02 sensor sounds similar to a problem I had a few month back.

distributor cap, rotor, wires, spark plugs?

EDIT

nevermind... reread your first post.

Doubled up my ground from battery to chassis, block to chassis, and positive from alternator to battery. Didn't make a difference. Also ran a fuel pump pressure tester in the fuel rail, about 48 psi. And measured when it was acting up also. I might go buy another new o2 sensor tomorrow. I don't care to spend, I just need my daily driver back. It runs halfway descent when in neutral, or park. It sounds like it has a big cam, bad off timing when warmed up, even in park or neutral.

The only time I've had similar issues was when I had a sensor short. The sensor voltage feeds are typically 5 volts, you get a partial short and you may get 2-3 volts in. I'm not familiar with a an OBD 2 tester and whether or not it checks sensor input voltage. I do know from experience the on board trouble codes only pop when the sensor is out of range (out of the design parameters), You can get seemingly good outputs from the sensor with low input voltage, but it is essentially garbage, garbage in garbage out.

Another time I saw something similar, I had a chattering ASD relay. Hard to explain, but best guess is it was a ASD relay power in problem for the actuator coil (inside the relay) that was interrupted and a partial ground fault was trying to power up the ASD relay in place of the normal power in for the actuator coil inside the relay. The main cause was my security module, which in my XJ is a dealer add on and not in the PCM. I never did find the ground fault, my door buzzer sometimes works and sometimes doesn't, my seat belt light stays on all the time. I jumped the security module and now have good power in to my ASD relay and only minor gremlins.

You may have to test your CPS wires all the way from the CPS plug to the PCM for resistance. If you are sure the CPS is good, it may be in the wiring. Make sure to clean the connectors with a good electrical contact cleaner. I had a TPS that gave me fits. I eventually figured out somebody had sprayed the inside of the connector (on the contacts) with WD 40 ( I could smell it). It never showed up on my ohm tests because I always back pinned for a test after the connector.

You eliminate the obvious and then move on to the exotic. When I get really stuck, I start over again with the basics, like I mentioned before, compression, initial setup, good spark etc.

Something I haven't seen, but it sounds feasible that the vacuum inlet for the MAP is plugged? MAP issues will make it run really crappy and rich.

TPS issues will make it idle really bad (too low too high) and messes with your timing (and shifts).

CPS issues make it miss pulses, the PCM will compensate to a point, but if you get too many missed or weak pulses it will run like somebody stuck a banana up your tailpipe.

I'm going to put my old cps back on today and get my $80 back from the new one. Test the old one and it was good. And the connector is clean. I guess all it could be with the sensors is a short somewhere. All of my relays are good. And I know all of the sensors on the throttle body are good. So I guess all it can lead down to is a short somewhere? I've made sure my housing where my butterfly is is all clean.

As I was driving it to the shop last night to work on it, I guess the coolant temperature sensor went out, and that was my problem in the first place. Because I thought the coolant was at 200. It died in me twice, and by the time I got there, smoke was coming from the engine, turns out, it was at about 300 degrees and oil cooking from inside of motor. Barely runs now and burns coolant. Time for new motor. I appreciate all the help guys.

sorry to hear this- good luck with your motor swap.

When you put a new motor in there and if you use the same harness, do a standing voltage check on the light blue wire coming from the temperature sensor. Do an ohm temperature check to make sure the failure was in the sensor itself. If you get any voltage between the ground wire light blue and the battery negative you have an issue.

I was looking through the schematics and a flaky ground path on that sensor and you can pump the 5 volt volt sensor feed voltage backwards through the system. I sure don't know what the outcome would be, but it could explain a lot.

What I'm trying to say is make sure it was a sensor issue and not a wiring harness issue or you may have the same problem with your new motor.

jacob13mtb said:

As I was driving it to the shop last night to work on it, I guess the coolant temperature sensor went out, and that was my problem in the first place. Because I thought the coolant was at 200. It died in me twice, and by the time I got there, smoke was coming from the engine, turns out, it was at about 300 degrees and oil cooking from inside of motor. Barely runs now and burns coolant. Time for new motor. I appreciate all the help guys.

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DARN.

Good luck with the swap--post up if we can help.