P0133, P0171, Black Exhaust, Rough Idle, Poor MPG, Loss of Power Up Hill
I had a stalling problem and various engine codes. I did the screw fix to the computer and cleaned the connectors since it would stall when I pulled gently on the connectors and since the connectors were zinc and had oxidation. I also replaced the catalytic convertor because it was gutted.
2 months later, I'm now getting P0133 (upstream o2 sensor) and P0171 (lean condition). It is obviously running rich from black smoke and soot from the exhaust.
All plugs had black soot. I checked, gapped, and cleaned the plugs twice. Since all plugs looked the same, I figured it wasn't a bad fuel injector. Nonetheless, I added a bottle of fuel injector cleaner to the gas. I added a can Sea Foam with the previous problem as well.
I checked and cleaned the O2 sensors twice with an air compressor. Both were covered in black soot. The downstream had some physical damage to the exterior, likely from the backfires and gutted catalytic convertor from the previous problems 2 months ago.
Air lines, intake manifold, exhaust pipe from engine to catalytic convertor and such seem to be fine without leaks. I checked the suction on the hose running to the PCV. Seemed to have good suction though suction faded when it started to idle rough.
There is a power steering fluid leak. I cleaned power steering fluid off the connector of the upstream O2 sensor. I also sealed the connector wires with silicon to help stop oil from leaking into the plug.
When the problem started, it would idle rough like it was going to stall, but it would never stall. The black exhaust was also obvious since it would stain the ground. It gets really bad gas mileage as well.
The performance started to get worse where it wouldn't run well on the interstate or up hill. The instant mpg feedback seems to indicate very poor mpg (3-11 mpg) though sometimes it will temporarily obtain better mpg, typically after running a wide open throttle and cruising. I figure this might be from the catalytic convertor getting clogged.
I've tapped and cleaned the MAP sensor. Seems to be fine.
I haven't checked or cleaned the IAC or TPS though I plan to do that today. It does seem to idle high and back off slowly when pressing and releasing the gas.
The EVAC seems to click when the engine starts to idle rough. The engine seems to do ok for a few minutes before it starts to idle rough.
I am also considering soaking the O2 sensors in gasoline today.
Is it the upstream or both O2 sensors? My next course of action would be to replace the upstream O2 sensor and to go ahead and fix the power steering fluid leak.
I had fuel leaking from the tank one day when it was over-filled. This was about a month ago. I've backed off from topping it off. Haven't seen fuel leaking again.
Am I headed on the right track? I'm just sick of resolving these types of problems and hate blindly throwing parts at it. I have an 85 dodge truck with worse problems. I don't mind checking ohms and volts, I'm just not too comfortable with it since I fear crossing something up or not knowing if I'm doing something right.
Since you are already getting the O2 sensor CEL, go ahead and replace it. I would also do the downstream since the Jeep ran with a busted up cat for a while. To save yourself some headache, get either Mopar or NGK/NTK O2 sensors. Our Jeeps don't seem to like the parts store brands very much. This should clear up the codes that you have.
If you have fluids on your O2 sensors, I doubt that it is power steering fluid. That would be one amazing journey for that leak to take. If it looks/smells like power steering fluid, it might be a trans fluid leak. Check around the trans fluid pan for any leaks, or try to trace where the leak is coming from.
According to the Haynes manual, the soot on the plugs could also be related to the O2 sensors not functioning properly and giving you a bad fuel/air mixture. It also says to look for a clogged air filter or fuel delivery problems.
1995 ZJ 5.2L V8 318. 220,000 miles and still rollin.
the ps fluid leak is bad and is everywhere the fan blows it and gravity pulls it, and the upstream o2 sensor wire harness is directly in that path. i'm going to replace it tomorrow. it is $60 for the pump and reservoir at autozone.
the air filter is clean, like a brand new giant honda mower air filter. i'll go ahead and clean the aic with throttle body cleaner and check the tps as suggested by other threads. i'll check the volts on the temp sensors and clean the map sensor with electronics cleaner too. the plugs looks all the same and i've used fuel injector cleaner and sea foam on it, so i doubt there is a fuel injector problem. it could be a problem with the fuel tank leaking when it was over-filled, but i think that would just cause the jeep to really just run too lean rather than run too rich.
autozone has the bosche o2 sensors. advance auto parts has the ngk. i'll go to advance auto parts for the sensors. i think they're the same price on the sensors.
i have the old o2 sensors soaking in gasoline now. i'm going to remove them now from the gas to dry them to put on tomorrow morning. i get the feeling both need to be replaced due to the gutted cat, but i'll see if soaking them in gas will work. i felt like i was panning for platinum. i wish they did a core discount on the o2 sensors.
i'm tempted to crank it without the sensors to help get some of the soot out of the system before i put them back in cleaned. i fear that the new cat is full of soot now and is part of the reason why i'm getting such sluggish performance though under good running conditions it should clean itself.
i'll clean the aic and map sensor, though from what i've read, those things wouldn't have the drastic effect i'm having.
i've owned several jeeps. this is the first lemon. it was bought from an auction back in june. i've fixed so many things on it and still have more to do. i still have to fix the ac leak in the passenger floor. i already sponged out a ton of water. i'm a bit confused if unclogging it will cause it to drain in the floor or out the floor. i need to fix the infinity gold speakers with the repair kits where the rubber rings deteriorated (not sure where to find the repair kits for cheap) or get new cheap speakers from autozone. the automatic door locks on the drivers side aren't working. i connected the switch for the alarm on the driver's side backwards too. you have to lock the door with the key to unset the alarm. the driver's side back window doesn't work either. i did fix the driver's side window. don't have a clicker. was lucky to find a spare key under the steering wheel. only had the valet key. need to get some tires for it too. already replaced the brakes. seems to have a noise, like a worn bearing noise, in the passenger back area. replaced the liftgate struts but not the liftgate glass struts. did the usual tune up stuff and even had to replace the check engine light bulb. need to fix the noise with the driver's side door, fix the torn vinyl better, though the gorilla tape is doing well, and fix the headliner better than where the last owner stapled it. it will all be worth it if the transmission lasts in it. that is my biggest fear with a gc.
my first jeep was a cherokee sport, and the only thing i did to it in 4 years was change the oil and glue back on the shift knob.
Last edited by henrygeorge; 11-25-2011 at 12:08 AM..
I replaced the upstream and downstream sensor today. I'm getting no check engine light and the mpg doubled from 3-22 mpg to 6-44 mpg (upwards to 60 mpg). It also idles very smooth. Before I did the fix, the muffler blew out a cloud of thick black smoke, which I'm glad happened before replacing the O2 sensors.
I also cleaned the IAC. It was really dirty and clogged. I also cleaned the black soot out of the throttle body. My dad thought I was crazy that there would be carbon built-up in the throttle body until he saw it. He finally concluded it was coming from the PCV.
FYI, Autozone does sell a MAP sensor cleaner.
Next on the list are cleaning the MAP sensor, new tires, unclogging the A/C drain under the passenger floorboard, and getting a repair kit for the dry-rotted infinity gold speakers.
The previous owner was such a jacka$$, I had to replace all 4 brake rotors because they never had them turned or replaced. The pads weren't even worn though I still replaced them. Thankfully rotors are a lot cheaper than they use to be. I even got a few dollars recycling the old rotors.
There is a noise coming from the rear of the Jeep. I'm not sure if it are the drum parking dragging. It could be something else. I didn't even realize the rear had disc and drum brakes.
This forum has been a life-saver helping me troubleshoot all these problems on the 1998 Jeep GC. It isn't even mine. I'm trying to help my ex-girlfriend fix it. The computer connectors being oxidized and the screw-fix for the computer was a life-saver.
I'm missing the 1999 Jeep Grand Cherokee and the 1996 Jeep Cherokee Sport. I'm not missing my 1998 Jeep Grand Cherokee. I had a transmission go out on it and traded it for a Liberty. One of these days I'm going do the smart thing and get a Wrangler. I did live with a girl who I helped negotiate a great deal on a 1999 Wrangler.
The car had a couple of random stalls for no reason, once going 70 mph on the interstate and another time while stopped. Drove fine without a problem for a couple of days after that. There are no engine codes. Not sure if there is just carbon built-up that is still cleaning out, fuel injector problem (I'll add more fuel injector cleaner and use throttle body cleaner), or something else. I still have not cleaned the MAP sensor. The only thing accomplished on the former to-do-list was getting new tires.
Window dropped and key lock stopped working on the driver door. I fixed the door lock with just reconnecting a linkage. The window regulator had a torn nylon bushing so I made a new one out of nylon.
I drained the battery while fixing the window because I left the key in the ignition while crafting a new bushing for the window regulator. I recharged the battery, and the idle was rough when I first cranked it because it was trying to idle too low. I tightened the negative battery connector and added a washer because it seemed a little loose. Seemed to get better once the battery got a better charge. The next day there was a back-fire. I'll need to fix the muffler tonight because it is loud. Still no engine codes but it hasn't stalled either.
Two stalls and a back-fire over several days with the jeep being driven everyday for a 1 hour commute each way in Atlanta. No engine codes. I've replaced the O2 sensors and catalytic convertor. I've also fixed oxidized connectors and the gc torx screw fix with the computer. I've cleaned the AIC valve, replaced and recleaned spark plugs, replaced the dist cap, and replaced spark plug wires. I've ran sea foam, enzyme fuel injector cleaner, and regular fuel injector cleaner.
the automatic door locks on the driver's side have never worked. the rear window on the driver's side doesn't work either. it would be nice to resolve those issues. i'd probably need an electrical schematic or guide on determining the cause of that issue since it doesn't seem like a mechanical failure but an electrical one.
i have no idea where to find a speaker repair kit for the infinity gold speakers. the factory cd player ate a cd too. it would be nice to get a cd player. i'd put a new cheap system in it, but it would be nice to stay with the factory stereo system because the factory system does sound good when it works.
old jeep gc are such a pain. i'd recommend to never buy an old gc unless you know everything works. if there are just 1 or 2 problems, there are probably a lot more problems you haven't noticed.
yes, 60 mpg when the car is coasting at a decent speed. that is what the jeep computer indicates anyway.
Last edited by henrygeorge; 12-13-2011 at 05:46 AM..
It's possible it's the 02 sensors IMO , new -yes , Mopar OEM , no . It's been said some aftermarket stuff causes issues . You could try what I said , unplug the upstream (close to engine) 02 sensor and drive a few days with a CEL . If it runs w/o issue , buy a Mopar replacement .
Mopar sensors are highly recomended for the 96 and up OBDII systems .
If your 02 checks out , you should confirm good fuel pressure . Followed by a crank sensor check and possibly a new coil . Maybe that PCM connector needs better cleaning Maybe the battery connection is not so great . That would be my check list .
MPG's are a touchy subject with jeeps , if you get better than 15 , no one believes you . Overhead consoles guages are no very accurate , some are , some aren't .
looks like i'll have to go through and clean the plugs, clean the battery terminal and replace the battery connector though voltage seems good on it, and deoxidize the computer connectors again, though tests seem good. d/c devices are sensitive. didn't know if a very infrequent back-fire or stall would be something like a tps.
i saw an 84 mpg reading today on the instant feedback while coasting around 45 mph. mpg does seem to have dropped back down in the 16 mpg range. it was running in the 18 mpg range. i'm guessing carbon clogging the cat. i assume the o2 sensors and plugs would self-clean. i'm use to seeing 18-22 mpg in a 99 gc, depending on highway traffic. lucky to get 14 mpg in a wrangler. worse than a chevy truck.
she would probably be happier with a working stereo than anything. pulled the muffler back together tonight so she could hear one. i might just pick up 4 cheap speakers at autozone if i can't find a speaker repair kit at the audio stores. it would be nice to find an oem replacement cd player.
i need to search the threads for the automatic door lock problems and rear automatic window not working on the driver's side and to fix the horrible noise the door makes when opening and closing it. i hate that her first jeep experience is this lemon, because i'm sure it will be her last jeep experience.
Last edited by henrygeorge; 12-14-2011 at 12:07 AM..
I have just went through all your problems I put new plugs,wires,dist.cap rotor, IAC, cleaned T-body, new up & down stream 02 senors(bosch are also good ones) new CAT and muffler. Dont bother with the PCM anymore just buy a NEW PCM that fixed all my problems purrrs like a kitten now. But I recommend fixing the CAT,muffler and 02 sensors after the NEW PCM, the old PCM isn't working right sending bad fuel/air mixtures it can destroy 02 sensors and CATS overtime. If you just replace them and leave the old PCM they could destory new parts. All these people say clean the connectors or wiggle the wires or do the screw trick its all bullsh^%. You are just rigging it for awhile if you want to get runover on the road doing 70 in the left lane trying to get over because your jeep died fine. Dont be cheap like most of the others buy a NEW PCM only $200 to $300 you have already spent that much aleast a bet. GOOD LUCK
there was another stall and then backfire today. i'm suspecting fuel pressure. there was a time when the gas tank was topped off, and there was a leak from the gas tank. with the really high mpg when coasting i'm suspecting the fuel pump at the tank is bad and has a leak, causing low fuel pressure. the 4.0 i-6 does seem to lack some power. some "mechanic who knows everything about cars" from the step-family did put some miracle fuel additive for passing emission tests in the fuel tank to try to get it to pass emissions when i wasn't around. i'm guessing the snake oil damaged the fuel pump gaskets. a fuel pressure check would be in order before dropping the fuel tank.
if it was the computer, i'd think the problems would be much worse and more erratic. the jeep would probably not run if there was damage to the computer. the stalling was much more frequent when the connectors were oxidized. the torx screw fix might be bull crap. i just did it because it is mentioned as a common problem. the zinc connectors manufactured from japan was a big headache for xerox. the service technicians had to use deoxy on them all the time. spraying the connectors made that original problem disappear. you're better off cleaning the connectors than replacing the computer. replacing the computer only cleans off half the oxidization. replacing the computer costs $200-300. a can of electronics cleaner or bottle of deoxy costs $5-10.
i might want to check and clean the o2 sensors and plugs again. cleaning the map sensor, throttle body, and adding more fuel injector cleaner probably wouldn't hurt because of all the carbon the bad o2 sensors created. it could be just left-over carbon entering the system and being burned off causing the problems. cleaning the pcv valve probably hurt either. i should also double check the battery, clean the terminals, and clean the connectors to the computer again. the low idle when the battery died did have me concerned. unfortunately, i'm not driving the jeep when the backfires and stalls are happening to really tell what is going on. if i'm really motivated, i could do a test on the ignition coil or cps, but i doubt those are the problems. the symptoms don't seem to indicate those things.
Last edited by henrygeorge; 12-14-2011 at 06:57 PM..
Trust me, you need a PCM. I went through the all the same troubles you have gone through. What is happening is that the electrolytic capacitors in the PCM are going out....and the solder joints on the harness plugs in the circuit board just plain suck. The entire unit lives in an extremely hot and dirty environment and the discreet components arent the best quality to begin with. It will throw all kinds of codes at different times. This is all assuming you have a good CPS and GOOD battery, a clean ground to the body and tight, clean PCM plugs. Jeeps like clean power. What you'll be getting in codes will be a "12" ( using the odomoeter codes), a 43, sometimes an 11 and a 55. The 12 is a B+ disconnected state.
The 43 is a misfire. ( duh)...the occasional 11 is a CPS as I recall and the 55 is end of codes. Mine threw every code in the book at different times....but the constant was the 12. I replaced the PCM and it was fine for a year....but guess what? My $249 lifetime warranty PCM is beginning to do it again, so I'll order another one from another place and return the lifetime warranty one for a backup replacement. These PCMs are the weakest link on these models and for the life of me I dont know why they located them in the engine compartment.
i ordered a new computer tonight. i also replaced the map sensor and went ahead and replaced the power steering pump in case the leak was shorting the o2 sensor. what a pain. i checked and cleaned the carbon off the o2 sensors (and cleaned the power steering fluid off the connector of the upstream o2 sensor with electronics cleaner and the air compressor). the rear one was blown out so i replaced it. i'm hoping i haven't blown out the new cat convertor too. i cleaned the throttle body with throttle body cleaner and the tube for the map sensor and housing for the iac (i had previously cleaned the iac itself). i hope i haven't damaged the iac. i cleaned the computer connectors. i can mess with the computer when it is idling and sometimes it will cause the engine to sputter and drop idle, but can't reproduce in a reliable way and is probably just a coincidence. i haven't touched the tps or cps though it sounds like the tps would cause a dead spot rather than rough idle and the cps would cause it to stall when it got warm or not crank at all.
i had a shop diagnose the jeep. the mechanic suggested new plugs (misfire on cylinder 6) and a new computer (bad signals from the computer) and suggested to go ahead and replace the map sensor. he tested for vacuum leaks and tested the fuel pressure which was all fine. he also suggested a new muffler though i pulled it back together again. he didn't seem too confident he knew what was causing the problem, but i'm trying a new computer. i ordered one for $179 from auto computer exchange in davie, florida. i think they ship local to me out of atlanta.
i'm getting a lean condition code and sometimes an ignition coil code. it cranks and idles smooth, then, the idle drops to around 800 rpm and starts to idle rough with a sputter. when coming to a stop, the idle will drop to 400 rpm and then back up to around 800 rpm. the engine is smooth otherwise. there is still some black soot coming out the exhaust and the mpg is in the tank.
no backfires lately. i taught her how to drop it into neutral to rev the engine when she comes to a stop.
would like to solve this problem so i can fix the speakers and rear driver side window and driver side automatic door locks. i might replace the stereo and speakers with a cheap auto zone system since the cd player ate a cd too. would be nice to fix the stock stereo system and find a speaker repair kit.
Last edited by henrygeorge; 01-10-2012 at 05:23 AM..