1998 Grand 4.0….Went through the whole fuel system. Replaced fuel pump assembly and filter (all one unit inside the tank in the rear). Replaced fuel injectors. Pulled the distributor and inspected it. Went through ignition system. Replaced ignition coil, distributor rotor cap, replaced wires, and installed new plugs. These exact symptoms were my issue and no matter what key words I typed or how much I searched I couldn’t figure this out! So I went step by step troubleshooting my way into oblivion! I even replaced worn parts of my vacuum hoses. Still the same symptoms persisted! My whole top end was rebuilt too early on to these symptoms 2 years ago. Head was removed, ported…polished…new gasket. Woke up today and took it to my local mechanic who rebuilt my cylinder head and had him throw his code reader on (even though no check engine light EVER came on). Code read “cylinder 4 misfire.” )Cylinder 4 is the last cylinder closest to the windshield). So I figured- A: it’s a bad plug by chance …even though it was replaced a year ago when my head was rebuilt. And even though I also physically checked ALL plugs were receiving a spark OR B: Oxygen sensor! Typed in “cylinder 4 misfire” and your video popped up. Dude the way you described the symptoms was SPOT ON and I immediately went to the parts store and got an “Upstream sensor 1” part I snipped the wires and threw on a 7/8 impact socket onto a long breaker bar. Hoses down the old O2 sensor with weasel piss (PB blaster) and kept the Jeep running. Blocked the back tires and had it up on ramps. Laid down from the front - end side and the sensor is right there! ( Be extra cautious if you do this because the tan blade is right there above you and will most definitely fuck your day up more. Wrenched down on her pushing away from me (lefty loosey) and she came right out with some hard effort. Brace your back against the passenger side front tire for leverage. Note*. Flash reset your computer by unhooking the ground wire from the battery with a 1/2 inch wrench. Do not let it touch the terminal and go turn on your light switch on and off a few times. I also go through the motions of turning the engine on and off and hit the blinkers. Basically you are discharging any remaining power in your electrical system. Hook the ground wire back up and you are golden! Any code should be wiped and the computer will relearn your driving behavior and will adjust to the new sensor readings. Giving your better fuel economy and peace of mind. Cheers

Dude, thank you for the tip. I have a 2004 wj with the 4 o2 sensors. It started running bad for a few days and tons of black smoke out of the exhaust and then over the course of a few minutes it would literally not move above an idle while in gear. I could put it in park and rev it to the limiter but once in gear the gas pedal literally did nothing. I received tons of advice from "mechanics" and they all said spark plugs, coils, injectors, IAC, TPS, clogged fuel filter and clogged cats. However none of them could explain why it idled fine and could be revved in park which wouldn't happen if they were the issue. But alas with no smoking gun I started with the spark plugs since I had never changed them in the 80k miles I've driven it and i bought it used with 99k miles and had no idea how old they were to begin with. The electrodes were severely worn down and the gap was easily twice the factory distance. So I thought that had to be it... Nope. No change. Then because of the completely dead gas pedal I thought maybe the TPS. Nope, replaced it and cleaned out the throttle body with no change. I knew from a previous check engine light that one of the downstream o2 sensors was failing and saw that they were a common problem on the 4.0 so I replaced both of them and the oil pressure sensor that was failing randomly. Still no change. I was defeated and ready to take it to a mechanic for the first time since I've owned it. But then going down the rabbit hole one more time I found your video and while it wasn't exactly the same symptoms it was pretty close and easy to test. I unplugged the 2 upstream sensors the next day and it finally drove down the road like normal. I replaced them both and it's running great now. Thank you!

Been struggling 3 months with this problem and today I found the problem. Great video 🙏🏽

Totally solved my 98 cherokee 4.0 misfire. Thanks man

I’ve been looking for a solution for my ‘98 Tj 4.0 for 6 months!! Your symptoms/diagnosis were literally word for word the same problems I was having. Couldn’t find anything on the internet about it until now. Thank you so much sir!

THANK YOU VERY MUCH ! Replaced the upstream (pre-Catalytic Converter) O2 sensor in my 1997 Jeep Straight 6 .... runs like a TOP !. No more intermittent BAD! misses like for the past few years with multiple expensive random parts replacements. Almost like getting a new car ! Also very good explanation of the function of the upstream O2 Sensor ! Thanks again!

I can not believe this is working so far. I have a 99 Cherokee XJ and it was cutting out, rough idle and very intermittent. I did the cap and rotor, it needed it, crank sensor, cause my scan tool showed it dropping out on the graph, and now I watch this and so far it runs fine. In COLLEGE, Associate in Automotive Science, the book says that a car will go into open loop when it throws an emissions code. SOOOO, in theory it should not effect the running of the engine because it is in open loop running a predetermined set of parameters. Followed your tips and so far so good. Thank you for posting this and now I can get my Jeep back on the trail.

Holy MOLY THAT'S WHAT'S HAPPENING. This is EXACTLY what I needed. You explained EXACTLY what I've been going through for months, but it would throw a Cam sensor code and then the code would shut off. I'll see what happens if I just unplug those O2 sensors tomorrow. DANG man I wish I would've watched this first. I thought it was a tranny problem with shifting.

Literally happening to me started smiling when you mentioned it goes away and comes back. Gonna go unplug my 02 sensor see how it goes. Thank you

I know it’s a couple months old but your videos are some of the best. Kudos

Hi Dan, I know I am very late to the party but you legend, you are the only one I have found to explain this with a good demonstration, keep up the good work, another Aussie happy to sub to your channel.

Dan you saved my wallet, been watching your vids for a while learning new things about my Cherokee and every time you make a video i learn something!!

Man thanks so much for this video. Had this changed in 15 minutes. This has been maddening for the last few months.

Dan H I owe you my thanks, this finally pointed me to my problem on my 98 XJ. Oddly my CEL wouldn't come on when I unplugged the sensor but it behaved just like you said and ran ok when forced to run in "Open Loop" fuel mode. One extra thing to be sure - I put my code reader on and used the setting to watch live data and there is was, the o2 was drunk ordering drinks haha and spiking wildly out of expected voltages and messing up the fuel trim % values. So I watched this video twice maybe 3 times then had my own battle with it today and won in the end. Bosch o2 in and finalllly behaving after hot starts. Much love from Ireland and keep up the good work!

Man you couldn't have been more perfect on your timing of this video. Just got a call yesterday from That Jeep Girl that got that lift kit and she is having this very problem in her 98 ZJ

Bro you're an absolute legend! Just pulled it out and she runs like a dream. Here's me thinking it was the cheap ignition cap

I believe your making these videos just for me lol. Thanks for the great tips

Hey Dan, Great help for our 98 XJ that I was beginning to believe was possessed. This is the third O2 sensor, tried Bosch, NGK and Mopar. Think I need to check the ground. Well done with the "seat belt PSA"!

Great video, your attitude is also great man!😊

I put my faith in the “o2 socket wrench”.... i got the o2 sensor out as well as all the threads 🥴 ripped out the threads and had to tap new ones...thank goodness it worked. haha the box end wrench is the way to go all day! This was years ago. Glad you got her going again ✌️

Retraction Please! Dan, I take it back. I left my battery disconnected overnight. My ‘97 ZJ ran GREAT all day long today and I’m looking forward to tomorrow and a trip to buy the new replacement O2 sensor. You were right all along ......I love your videos. Keep uploading...best, KS

Wow, thanks man! So I changed the transmission cooler lines on my 96 this past weekend. ( hard lines from the transmission all the way to the rad hoses). Not sure if you ever did that but it wasn’t fun. Anyway after I dropped the exhaust to put the new ones in, I noticed I had the same issue that you did in the beginning of your video along with a P0170 code. Turns out I must have messed up the o2 sensor working in that area. Fix one thing, break another. Sounds about right for me. Thanks for the helpful tips as always

Having similar issues with an 01 and this answered my questions. Thanks for the video. Liked and subbed.

Once again Project Dan H keeps a older Jeep on the road and out of the scrap yard 👍🏻

Dude I have a 99 tj doing exactly this, I’m so glad I seen this video. Thank you bro!

Dude. This video saved me a lot of time and money on my Ram. Thanks brother!!!

O2 sensors are a pain. Great video man

I had the same problem with the cheaply made 02 "wrench" I went and got the deepwell socket style now and man what a difference. Couldn't help but notice you have the "pre-cat" Y-pipe (CA/NY emission system) Take care not to damage that Y-pipe as there are none in existence any more and no aftermarket units exist. Had to use the "Federal Emissions" pipe (non-pre-cat) and had so many issues with BOTH the 02 sensors. Went through several different ones until we got the CEL to stop coming on. Go Grievous!

You the freakin man, Dan! Keep the ZJ alive!

Awsome vid. I have an 07 that is giving me the exact same problems that your vehicle was giving you. Changed plugs, no help. Changed coils, no help. Gonna try the O2 sensor next. But it looks as though getting to it is a bit harder than yours. Thanks.

😮 omg this is totally what’s happening to our 99 Sahara. Love the video and how in detail it is, thank you 😊

Hi Dan, I have a suggestion. Your videos have helped me with EVERY project I’ve undertaken so far (right down to re-soldering the driver-side master window switch!)with my ‘97 ZJ.....with one exception. Fueling my ZJ is a real chore due to the fact the pump nozzle shuts off every ten seconds. It might go a little longer if I adjust the angle, pull up or down, or back it out a little. After watching a few KZfaq vids it’s apparent there’s an obstruction somewhere but I won’t attempt tracking it down until I’ve seen you do it! Thanks! KS

Great video. This is exactly the problem on JGC

This is exactly what my zj is doing, going to try this. Thanks for the info.

Great video and helpful. I have an 1999 4.0 XJ.

U just saved my life bro my girls Miata is doing this ive spent so much I didn’t know this till now...lol I bet this is it nice vid man...

I had this exact same problem in my 97 ZG. I was 1000km from home when it started using double the normal fuel consumption and running poorly. Dropped it into the Jeep service centre when I was near home. Left it there for 2 months and no-one could figure out the problem. The scanner didn't show up the error. It was destined for the junk pile but I took it home and after weeks of trying everything, I eventually unplugged the oxygen sensor and it instantly started running normally. Nice vid, too bad this all happened to me a few years ago when this info was not available!

Great video my unk having the same problem and I love the here we go again instrumental

When that Oxygen Sensor wrench broke I was like bring out the heat! That wrench wasn't built for the power of Dan.

nice video - heat and a 6 pt wrench always are your friends ! May be anti seize is helpful before hooking up the new O2 sensor.

dan the video quality is amazing what are you using ?

Great video, about to do this on my 1997 ZJ Orvis here in the UK.

Love your videos brother, I see your from NY maybe run into you one day …just got 97 Zj and your videos help a ton.. my girl hates how our spare bedroom looks like your garage lol

Hey Dan,you use a deep well socket,crows foot wrench or the box end you used or a pipe wrench if all else fails you use the tool to install the new one!!!!

Your video helped me immensely....👍🏻👍🏻

Dude you explained my issues completely Ima tell ya of it did the trick for me 😀 . Thanks either way and good vid. I'm still subscribed

heat can be your best friend nice job Dan

Bro I replaced everything on here thank you so much it was the o2!!!🙏🏻🙏🏻

This is a awesome video bro thank you for sharing you help me out with my 1995 jeep 👍

Hi Dan, just letting you know changed the O2 sensor today. Needed a lot of heat, removed the front wheel for better access, used a long bar and it shifted. I also cut the old one down to get a six sided socket to fit. Had to use the old multi plug and solder it to the new wires but all good and running sweet from cold. Thanks for a great video.

Thanks. My 1997 is having exactly that problem. Had no clue.

You just earned a sub , SAVED ME SO MUCH $$$

Thank you Dan.

Worked on my 98 zj, thanks!

Awesome. you are only guy with my symptoms. Just unplugged, but no real runnjng time yet.But, you are spot on with fuel consumption. I lost over 1 mile per gallon when I noticed it.

Solved my problem! Thanks for the help!

Keep up the good work broo

Fantastic video brother

breakfast video with dan h...awesome...my breakfast consisted of potato chips! yum!

well got the o2 put in on Wednesday and no issues. the hesitation is gone runs better feels like more power, but we know that's not true. thanks for the video now im going to make a video of my 96 my channel is called project xj

Super good video!! great explanation !! im gonna disconnect mine tomorrow and see if it works 👍🏽👍🏽

Great Info! I hope they gave you your money back on that socket!

I just cut the wires off put my impact socket on it and spin it out 😂 I use the O2 sensor socket to reinstall the new one if it's a tight space an old pipe wrench works too . My old ZJ would run better with the O2 unplugged and it get better milage but I replaced the O2 sensor because of inspection was due . Great video DanH and a little heat goes a long way 👌

Project Dan,you da man!

Thanks for the tip👍🏻😆

Such lovely cars. Better than the newer stuff.

Great video!!! Thanks

Great content brother, helped a lot thanks dude

Good info thanks man!

Outstanding Thank you

Hi, I have been banging my had on fine starting poor running 91 XJ. Pulled out gas tank, done ultrasonics to injectors twice, flushed the fuel lines, measured fuel pressure, new ignition cap an cables, coil etc... Nothing bad since it is 15 years sitting barn find. Now - this is to be tried next! Thanks!

I'm tryin this next! I just swapped the TPS, slight improvement but still bump'n jump'n.

You're lucky. I've snapped the bung off before. Now I price compare and plan on replacing exhaust parts.

I believe my o2 sensor is drunk!! lol Great video. Thanks.

Great video I’m about to unplug my o2 and see what happens ...wish me luck. BTW that’s a sweet Jeep Mines a 99 XJ

Thanks Dan o...Dan h!

Another great job

Great vid,thanks

Nice job Dano.I just replaced all 4 of my O2 sensors.I had to use the torch and PB Blaster.I bought that same offset O2 wrench at HF and it worked just fine for me.You must have got a bad one or it was just your brute strength...lol...Take care brother.....

Good job....did you had any codes ?

Dan you're the only one that I would know who would know this. I ripped my downstream o two sensor out of my two thousand x j and it seems to have a three wire sensor I need to know which color wires go to which color wires

Bro. I've been trying everything. I'll try this out next.

Sure appreciate this video....... Thanx

Good video. My Astro van has multiple misfire I changed spark plugs and wires and distributor cap and roto. Scanner show now the oxygen sensor

My 97 Cherokee has been having a Cyl 1 misfire that does it with no rhyme or reason, randomly in all sorts of different conditions...I should give this a shot.

Noticed your rear main seal was leaking, I put that off forever on my TJ. Finally changed it over last winter... it now leaks worse than it ever has this summer lol some things are best not repaired

Hey Dan, quick question, did your MPG improve after plugging the new sensors? (I mean new/good sensors vs. fixed/open loop operation/unplugged sensor)

Great video, I have the same issue but my car fails on the interstate and then I have to sit for a long period of time. I never know how it is going to run. Thanks alot, I know I can unplug it until I can get another part and replace it.

Great video

Man thanks jeep dealership could not figure it out it out thanks to u my good woohoo lol

You are the best thaaaaank you so much my problem just solved

I'm having exact same issues. Only codes popping up. But I unplugged it and the check engine light never went off 🤣 I'm replacing it in a few days here.

Hey Dan! Yeah, I purchased the socket version of the O2 tool years ago. I found out the same as you, on the old sensor, cut the wire and use a tool that grips on the hex. You can use the tool to install the new sensor. So no luck on the power steering pump bracket? Thanks for looking any way. Guess I'll have to take the time for a yard trip. Should have done that in the first place. Does this problem also happen with pre OBDII Jeeps as well? (Bumble Jeep is a 95) She runs good now, but fuel economy is awful (10ish). God bless, stay well.

I would love to get a drink with some o2 sensors one day. They sound fun! Haha

Had the whole car moving trying to get that 02 sensor off 😂. Great video! Looking into get a Jeep Cherokee any suggestion on best place to buy one? I live in southern Utah(2hours from Las Vegas). Thank man!!

Hi. Mine 2000 wj starts up ok too but has a murmer little rough spot and idle only. Runs great street and Fwy. But that's cause I replaced the spark plugs, fuel injectors and fuel pressure regulator. That's how these Codes po172 and po175 showed up. So Bank 1 and bank 2 running rich per my OBD2 but don't show which sensors. Are these both up streams and where are they located. Thanks

Well I'll be dinged. Unpluged o2 and it stopped thank you it has been bugging me for 6 months. Thank you.

thanks, I'm having that issue only after i start it every time and now when i give it gas it does it thanks for the test. i have a 96 xj country.

I could not stop laughing when the harbor freight socket broke!😂😂 happened to me to!

Same story as in your video. So I went ahead and order a new O2 sensor Upstream. Replaced it and now I haven't even worse misfire. Maybe I damaged the O2 sensor during installation or maybe I just got a cheap brand from Amazon