Very odd idling issues

[Tim_MN]

Fix all known deficiencies and defects. You cannot properly diagnose problems if there are known faults/defects/missing parts.

Is or was the CHECK ENGINE LIGHT on ? If there are, or were, any stored CEL trouble codes, your Jeep is trying to tell you what is wrong. Trouble shoot and diagnose based upon the trouble trouble codes.

What were the results of the Load Test on the battery ?

 

[Czjeeper]

The computer will never let it look for more codes with that O2 missing. Also, you may not be reaching closed loop.

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[8Mud]

The wiring and connector for the rear O2 are notorious for cooking on the exhaust pipe. The wiring holder has a flat press-on nut that is really hard to get off in one piece. Many break the nut off and never bother to tie the wire up out of the way and safe. The stud for that flat nut has M10 threads, use a regular old M10 nut for a cable holder. More than a few have blown the O2 heater fuse when that wire melts.

 

[McQue]

directly from the 1997 Factory Service Manual regarding fuel pressure...

"Normal operating pressure should be
339 kPa +/- 34 kPa (49.2 psi +/- psi)

The fuel pressure should not drop while motor is idling. There are no sensors that control the fuel pressure. It is simply a pump.

Your first post says the pressure drops to 30.

 

[Ahvicha]

directly from the 1997 Factory Service Manual regarding fuel pressure...

"Normal operating pressure should be
339 kPa +/- 34 kPa (49.2 psi +/- psi)

The fuel pressure should not drop while motor is idling. There are no sensors that control the fuel pressure. It is simply a pump.

Your first post says the pressure drops to 30.

The pressure drops only when the engine is off. But fairly quickly.

 

[Ahvicha]

Fix all known deficiencies and defects. You cannot properly diagnose problems if there are known faults/defects/missing parts.

Is or was the CHECK ENGINE LIGHT on ? If there are, or were, any stored CEL trouble codes, your Jeep is trying to tell you what is wrong. Trouble shoot and diagnose based upon the trouble trouble codes.

What were the results of the Load Test on the battery ?

So the Jeep is just giving me the battery code and then end message code. Considering I’ve had the battery in and out. It would make sense. But I’ll be taking a little more detailed of a look her soon

 

[Ahvicha]

The computer will never let it look for more codes with that O2 missing. Also, you may not be reaching closed loop.

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I would guess after about 5-8 mins I’d hit closed loop unless the engine. Just never enters closed for some reason? I’m not sure. Again. I’ll be checking some more things today

 

[Ahvicha]

Fix all known deficiencies and defects. You cannot properly diagnose problems if there are known faults/defects/missing parts.

Is or was the CHECK ENGINE LIGHT on ? If there are, or were, any stored CEL trouble codes, your Jeep is trying to tell you what is wrong. Trouble shoot and diagnose based upon the trouble trouble codes.

What were the results of the Load Test on the battery ?

Oh and they never told me what it read. They just said that it was good. And wouldn’t say anything else. So I just took it and said whatever. I just bought the battery a month and a half ago and don’t really suspect it. There’s no way I can read a battery at home is there. With a multi meter.

 

[Czjeeper]

I would guess after about 5-8 mins I’d hit closed loop unless the engine. Just never enters closed for some reason? I’m not sure. Again. I’ll be checking some more things today

With a hard fault like a missing O2 sensor, the OBDII computer will stop running monitors. It may not be letting you reach closed loop. You WILL NOT know without getting live data. Buy a data enabled Bluetooth device for youe phone if you can't/won't get it hooked up to a scan tool. I've been a driveability tech for the last 10 years. I wouldn't suggest this without a reason.

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[Rob Mayercik]

Oh and they never told me what it read. They just said that it was good. And wouldn’t say anything else. So I just took it and said whatever. I just bought the battery a month and a half ago and don’t really suspect it. There’s no way I can read a battery at home is there. With a multi meter.

You can't really do a load test, but there's a couple simpler things you can do:

1. Put the voltmeter on the terminals and watch volt reading while cranking. If it drops below 10.5V while the starter is spinning the engine over, the battery is either bad or grossly undersized for the job

2. With engine running at idle, check voltage at terminals - if the alternator's working properly, you should see at least 13.5V. If you see less than 13V, the alternator is either not capable of charging or the ECU is not signaling it to do so. If you're not seeing evidence of charging, and while idling you see the voltage sag below 12V, the electronics are going to start shutting down - they're not generally tolerant of the supply voltage being too low.

Alternately, if you have a Harbor Freight nearby, they have a 100A battery load tester for $20 - might be worth a punt:

https://www.harborfreight.com/autom...ning/100a-612v-battery-load-tester-61747.html

 

[Ahvicha]

Soooooo yes the cat is missing as I thought. And luckily I instantly found the plug for the down stream tucked away unharmed. So needless to say next weekend is a cat and a 02. I’ll put updates when that happens. How silly of me to absolutely miss this. Wow. Anywho another question. Do you have a recommendation on a cat by chance. I’m going to buy the AP emissions part number 645327 for 163.79 on rock auto. It seems to be the favorite. Any emissions experts out there? My state doesn’t require any emission stuff. I just need a good one that won’t choke up the system.

 

[Unclewolverine]

Unless the 02 sensor is down stream of the cat, (can't remember on 97+) then the cat don't matter. And if you don't need one for inspections, (like kansas) don't waste your money.

 

[lawsoncl]

Same price on Amazon with free shipping. Rock Auto tends to be expensive on shipping, for me at least. Depending on how bodged up the exhaust is, you might still need a bit of customizing for a direct fit. If that's the case, might be able to find a generic that has the right input/output and O2 fitting and save some money.

Oh, and use the band clamps instead of the u-bolt style clamps. Makes taking it apart or adjusting the alignment much simpler, versus the ubolts that distort the pipe.

 

[Ahvicha]

Unless the 02 sensor is down stream of the cat, (can't remember on 97+) then the cat don't matter. And if you don't need one for inspections, (like kansas) don't waste your money.

It is down stream of the cat. To be completely honest. I don’t believe this will fix the issue I’m facing. If you think about it. If your having idling issues the first thing is to unplug your oz sensor (down or up depending) and see if the issue resolves it’s self. If it does. Then you have a bad o2 sensor of course. In this Situation I already don’t have a o2 sensor down stream so in actuality this issue would be none existent. Or perhaps I don’t fully understand how the pcm works. But like someone else had stated. The Jeep might not be hitting closed loop because it’s missing info. So all in all we’ll see what happens. I ordered the part. This weekend I’ll put it on and come back with more news. To be honest I’d rather have everything there than not you know?

 

[Ahvicha]

I would like to note for anyone still here of progress. After doing the injectors. It almost seemed to of gotten better. Maybe that’s just me looking for hope lol. But I did take it for a good drive and and it’s COMPLETELY operable just has a slight hiccup when at a stop light or stop sign. Another note. I noticed the interior light under the dash on the passenger side was dimming out every time the car would miss fire as if it was the first thing to die. Of course the engine never felt like it would die just ran poorly. Could this by chance be related to anything. Or am I looking to much into this. Maybe it’s me but that seems alternator or battery related. But of course I came back to it today after a night or two and driving it and starting it up off and on and the battery is still good. So I feel like those should be ruled out. But I’ll do a check on the battery this weekend as well.

 

[Ahvicha]

alright. for anyone whos still here.
heres a note for this weekend.
i put in the new cat and the new downstream 02 sensor but still no dice. it is how ever running ''healthier''. but still just has a slight hiccup. it doesn't seem like it wants to die anymore. but just misfires every so often. runs fine. just wish it ran better. i did put a full tank of gas in it and some techron to help maybe clear out some of the fuel system and some build up in the chamber. but im still just so baffled by whats going on. maybe its just old but i just beg to differ. especially after looking at the compression on her. it seems like the first 1 of running we have no issue at all, but once we get warmed up and going it has a misfire, so it has to be something electrical. but what could it be?

 

[Unclewolverine]

Do you have much wobble in the distributor? the bushing can get worn so the rotor doesn't stay true. Check the coil for heat cracks too.

 

[Ahvicha]

Do you have much wobble in the distributor? the bushing can get worn so the rotor doesn't stay true. Check the coil for heat cracks too.

The dizzy has a 8th of a inch give each way. It’s wobbly but nothing id put a red flag on I guess. And the coil had a crack so I replaced it.

 

[Rob Mayercik]

That seems like a lot, but I'm not an expert on distributor tolerances...