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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Hello, everyone,
I am still really excited to get my XJ up and running but of course, things never go perfectly to plan and that's alright. My jeep is running really rich and won't rev past 3000 RPMs. These are the codes I'm seeing right now
12
35
33
22
13
15
24
I have checked my throttle position sensor and it is not over 4.96V in any position of the throttle and my MAP sensor didn't have a vacuum line connected to it for the first hour I was running it.... I have checked continuity and checked for any open or shorted wires to the air intake temperature sensor and coolant sensor. I have additionally replaced the MAP sensor and the throttle position sensor just in case I was missing something but I put the old ones back in because nothing changed. I have even visually inspected the PCM and check the grounds on it everything seemed to line up but I'm not great with protocol when it comes to PCM diagnosis. I have done an interesting test and that is that when I unplug the O2 sensor nothing changes and additionally no check engine light comes on, I don't know if that means I am having O2 problems or whatever. I very much feel like I am chasing my tail and am completely open to buying or testing whatever it takes to get this thing good and running.
I have 4 hole injectors and a cam if you guys need the lobe I will send it over. I have also tested the fuel pressure and it was in the 39 range at idle and rose as I gave it gas.
My father insists that it needs to go through its cycles and be ran but I think that is crazy talk because whenever I run it past idle for to long the exhaust gets bright red (he says it is because it is stainless steel) and I don't want to burn a hole in my brand new motor.
My personal conclusion is that I need to get an adjustable fuel pressure regulator because of the cam but I've always been told on here that the computer will adapt to these things just fine so I'm lost lol.
Let me know what you guys think, for god sake if I have to pull the whole darn motor out I will I am completely open to figuring this out and fixing the darn thing.
Few extra notes, I have checked the spark plugs. They were pitch black, no oil though so I don't think I have ruined my rings or anything really catastrophic while I was breaking in the motor as much as I could.
Running with the MAP disconnected will dump a lot of fuel into the cylinders and run really rich. As will a leaking injector. Are they the chinese knock-offs, and are they the right ones for your Jeep? Stainless will discolor in rainbow colors as it heats, but if it's glowing red you need to stop and find out why before you melt down and plug up the cat converter. If the temp sensor isn't working, it won't go into closed mode and use the O2 sensor.
Given how many codes you have, I'd suspect bad grounds and/or broken wiring. Most of the sensor grounds connect on the engine block under the bolt that holds the dipstick. Also look carefully at the harness where it crosses from the firewall to the engine, take the loom off and look at the wires.
Running with the MAP disconnected will dump a lot of fuel into the cylinders and run really rich. As will a leaking injector. Are they the chinese knock-offs, and are they the right ones for your Jeep? Stainless will discolor in rainbow colors as it heats, but if it's glowing red you need to stop and find out why before you melt down and plug up the cat converter. If the temp sensor isn't working, it won't go into closed mode and use the O2 sensor.
Given how many codes you have, I'd suspect bad grounds and/or broken wiring. Most of the sensor grounds connect on the engine block under the bolt that holds the dipstick. Also look carefully at the harness where it crosses from the firewall to the engine, take the loom off and look at the wires.
The grounds should be good but in going to inspect them again and confirm because those grounds are the only ones I didn't replace and just strapped back on the motor. I'm also going to purchase a Mopar temperature sensor right now as well. I have already inspected the loom that is closest to the fuel injectors and the wires to the PCM and surprisingly it was good. The fuel injectors are bosch 703’s that I got from a pick a part and refurbished myself, I think I'll send them out to someone to get them professionally cleaned if after all of these other things I still have problems. Keep in mind I did test them properly and they seemed perfectly fine.
Thank you so much for the help, I will get back to you once I've checked these things, I'm getting this damn thing fixed.
With all those codes the only thing running it will do is teach the ECU bad habits. And the ECU will learn everything about the current conditions, good or bad, in well under 5 minutes.
Running it with the MAP disconnected will have fooled the ECU into thinking it is floored so instead of 2% injector duty cycle it would have been somewhere over 20% or TEN TIMES more fuel than correct. That would account for the black plugs, a gallon of fuel in your oil and for the glowing exhaust.
If you are saying now that you ran it like that for an hour I would expect your cylinder bores are polished smooth from fuel washing. This will make a crap ton of wear and it will use a lot of oil. If it ran for an hour with a gallon of fuel in the oil I expect all your bearings and your lifters and cam lobes are damaged. If it ran for an hour glowing like that then your cat is certainly ruined and I would be concerned about your manifold and heads cracking from the thermal stress. I would also be concerned about your exhaust valves being burned out at the seats and the oil seals being baked brittle. You should also inspect any wires that are within a foot of that glowing metal. The heat will wreck the insulation and they will be brittle going forward.
The exhaust should only glow like that in a turbo application making 600+ HP., and you only want to do that for a few seconds at a time. There is a reason we drive around for years on an engine, but dragsters typically do a full engine rebuild at least every few runs.
You've got to get your sensors and codes solved before you run this engine to death. Short starts and runs are needed to check progress and such, but there are hundreds of ways to kill an engine running it wrong and one way to run it right, with very narrow margins surrounding that right way.
I hope you can pull this one back from the edge or that I've misunderstood the operating conditions. Good luck.
With all those codes the only thing running it will do is teach the ECU bad habits. And the ECU will learn everything about the current conditions, good or bad, in well under 5 minutes.
Running it with the MAP disconnected will have fooled the ECU into thinking it is floored so instead of 2% injector duty cycle it would have been somewhere over 20% or TEN TIMES more fuel than correct. That would account for the black plugs, a gallon of fuel in your oil and for the glowing exhaust.
If you are saying now that you ran it like that for an hour I would expect your cylinder bores are polished smooth from fuel washing. This will make a crap ton of wear and it will use a lot of oil. If it ran for an hour with a gallon of fuel in the oil I expect all your bearings and your lifters and cam lobes are damaged. If it ran for an hour glowing like that then your cat is certainly ruined and I would be concerned about your manifold and heads cracking from the thermal stress. I would also be concerned about your exhaust valves being burned out at the seats and the oil seals being baked brittle. You should also inspect any wires that are within a foot of that glowing metal. The heat will wreck the insulation and they will be brittle going forward.
The exhaust should only glow like that in a turbo application making 600+ HP., and you only want to do that for a few seconds at a time. There is a reason we drive around for years on an engine, but dragsters typically do a full engine rebuild at least every few runs.
You've got to get your sensors and codes solved before you run this engine to death. Short starts and runs are needed to check progress and such, but there are hundreds of ways to kill an engine running it wrong and one way to run it right, with very narrow margins surrounding that right way.
I hope you can pull this one back from the edge or that I've misunderstood the operating conditions. Good luck.
Honestly, I'm sure it's fine lol. Its a motor if it is broken ill get it rebuilt again but jumping to such extreme conclusions that the entire motor is blown when I just rebuilt it is going to put nothing but worry in my head and with my OCD just reading your message is giving me a headache haha. I'm not saying I'm a little ***** but be gentle on me Chaz I spent a lot of time and money on this
I appreciate your concern by the way. My dad is the one who told me the exhaust wasn't a big deal and I'm starting to trust him a little less when it comes to these things... I will pray to the gods up above that the motor is fine and I will be gentle on it.
Last edited by Griffyorcono; 01-26-2021 at 10:50 PM.
no way the exhaust should be bright red...are you sure the Cat isnt plugged ?..would stop it revving to...but it should throw a rear O2 code if it is (in an OBD2 vehicle anyway)
it might help us a bit if you converted those Jeep codes to OBD codes
realistically you have to be able to start the vehicle and have no codes, once cleared...if you cant something is still wrong
no way the exhaust should be bright red...are you sure the Cat isnt plugged ?..would stop it revving to...but it should throw a rear O2 code if it is (in an OBD2 vehicle anyway)
it might help us a bit if you converted those Jeep codes to OBD codes
realistically you have to be able to start the vehicle and have no codes, once cleared...if you cant something is still wrong
Well I have good news. I have no cat so we are good in that department. I don't want to backtrack and act like I haven't done something pretty stupid, so I'm just going to stick with I ran it for an hour but I have a feeling that is a strong exaggeration of how long I actually ran it. I have a mopar temp sensor and new manifold air temp sensor coming in tomorrow. For now it will sit and wait for those new parts.
I want to note though that the motor showed no other signs of trouble besides the exhaust being red and the fact that because it was getting so much fuel it would sputter and spit flames out the exhaust at 3000 rpm's and never go over that rev range. Chaz is not wrong fuel was as rich as it could be. My question is though don't I have to run it for awhile for the codes to clear on a OBD1 system? I have the computer unplugged to reset right now so we will see.
The reason I bring up the codes taking a moment to clear is because many of the sensors that are coming up with issues are ones that I have unplugged while the motor is running trying to test things And figure out what in the hell was wrong. I also don't get a check engine light when the vehicle is running, it is only when I do the key trick that I figure out that I even have codes lol.
Alright hoping maybe this was part of the issue. I went ahead and went over all the grounds I hadn’t touched and checked them. Me being an idiot I thought these grounds were fine they weren't, I believe this is the ground to the PCM which confuses me because when I checked the pcm for continuity in the ground port or whatever you wanna call it I was getting a reading which I always thought means that I have ground, I don't completely understand electricity yet though... Only like two or three of the copper strand in the wire were still connected so I assume that would create an issue when there is like 7 strands of copper total. Also none of these grounds were clean so they could've been creating an inconsistent connection. Replaced two of them and left one of them and cleaned it because it was completely intact. I also connected them to the original location cause that is where they belong lol I hadn't put them there previously.
Checked the loom that goes through the firewall since you guys told me to look at that and nothing was exposed so that should be good
Last edited by Griffyorcono; 01-30-2021 at 11:11 PM.
Additionally, I bought and installed a new air intake temp sensor and water temperature sensor.
I was planning on running it tomorrow but wanted to get your guys opinion. If there is no check engine light should I let it run and see if it learns a correct air to fuel ratio or only run it for a few minutes and then check the codes with the key trick?
I'm also going to buy an OBD1 sensor so I can get a clearer understanding of what is going on
For the grounds, what you found is one of the harder to catch problems. If you have the vehicle off and use the continuity or even the ohms mode it will test good. The problem is that when you actually load those wires while it is running all the flowing current can't fit through those bad connections and so you develop voltage at the frayed spot. That means the "ground" that the sensor sees is not actually ground, but a volt or 3 above ground. This tricks the sensor into making all kinds of lies depending on the sensor type. The test to catch this, that you don't usually need to do, is to probe in voltage mode the sensor on its ground terminal and the battery neg while things are running. If you get voltage you have high resistance somewhere in the ground that you'll have to bracket by testing at other points along that ground path.
Do you have the Factory Service Manual as a pdf? You really need it for doing the work you are doing. It is available. I think I paid $10 or $15 for the download of mine.
If I had to work on one as out of whack as yours seems to be I would go through the FSM to get the procedure to test and or calibrate each of the main sensors used to operate the engine. Crank position sensor, cam position sensor, O2 sensor, MAP sensor and verification of suitable oil pressure. Once you can trust those you should be able to run the engine steady without worrying about hurting it. Keep an eye on temperatures, exhaust smell and appearance while you are doing that and shut down and regroup if things are out of normal range. Then you can move on to the sensors that are more like tuneup items. Coolant temp, intake air temp, TPS, EGR, Tstat, fan activation...
Last edited by doublechaz; 01-31-2021 at 05:30 PM.
For the grounds, what you found is one of the harder to catch problems. If you have the vehicle off and use the continuity or even the ohms mode it will test good. The problem is that when you actually load those wires while it is running all the flowing current can't fit through those bad connections and so you develop voltage at the frayed spot. That means the "ground" that the sensor sees is not actually ground, but a volt or 3 above ground. This tricks the sensor into making all kinds of lies depending on the sensor type. The test to catch this, that you don't usually need to do, is to probe in voltage mode the sensor on its ground terminal and the battery neg while things are running. If you get voltage you have high resistance somewhere in the ground that you'll have to bracket by testing at other points along that ground path.
Do you have the Factory Service Manual as a pdf? You really need it for doing the work you are doing. It is available. I think I paid $10 or $15 for the download of mine.
If I had to work on one as out of whack as yours seems to be I would go through the FSM to get the procedure to test and or calibrate each of the main sensors used to operate the engine. Crank position sensor, cam position sensor, O2 sensor, MAP sensor and verification of suitable oil pressure. Once you can trust those you should be able to run the engine steady without worrying about hurting it. Keep an eye on temperatures, exhaust smell and appearance while you are doing that and shut down and regroup if things are out of normal range. Then you can move on to the sensors that are more like tuneup items. Coolant temp, intake air temp, TPS, EGR, Tstat, fan activation...
Well I have good news for you because I genuinely think I have fixed the problem. I have not run the vehicle yet but two of the grounds that connect to the alternator were not screwed down and simply barely touching the screw they bolt down on so again I AM CHECKING THE GROUNDS LIKE MY LIFE DEPENDS ON IT! Those grounds go to the ignition system so I am almost sure that is why I couldn't rev past 3000 we will see though I am not optimistic just determined to fix this damn thing.
Appreciate you Chaz you're a friend, don't know if I would've fixed this without you and everyone else’s help. Once I run it I will go ahead and follow the procedure of checking voltages like you're saying so I make sure that everything is working properly since based on what you said I have no more room for mistakes anymore and just need to pray that the motor isn't already toast in the first place... I also have an FSM from cruiser for my Jeep so I should be good I've been using my Haynes as well when I need it.
One question,
Should I change the oil.... I have oil and since you're saying there is a strong chance there is a bunch of gas in the oil I can drain it and add new oil?
Last edited by Griffyorcono; 01-31-2021 at 05:47 PM.
01-25-2021, 11:36 AM
Idle but wont rev past 3000 RPM
