brittmeister

Hello all,

This is my first time posting to this forum, but this site has been so helpful when diagnosing/fixing issues even without posting.

I have my '96 XJ 4x4, 274,000ish miles. I don't know what was done to it before I bought it 20-30,000 miles ago and I'm trying to fix it up and keep it going as long as I can.

So, here are my current problems:

1. I keep getting a code 11. I don't have a code reader (checking by turning key 3x) but according to my manual it has to do with the Crankshaft Position Sensor...which I've replaced. I've disconnected the negative terminal on my battery a few times and it's reset the code and my CEL has gone off...only to come back on again after about 10-15 mins of driving. I've tried to associate what is causing the CEL to come back on...and I can't figure it out. The CPS is a duralast...which I've read aren't as reliable as the Mopar ones...but why would it come on after 15 or so minutes? Is that how long it takes for the computer to reboot and check everything? I'm not really experiencing any starting/stalling/idling issues, but I just want the CEL to go off. I've added some dielectric grease as suggested in some forums, but still no luck.
   
   
2. My second issue is what I think is a heat soak issue...but I'm not entirely sure. If I try to start my Jeep after it's been hot (could be after 15 mins or it could be overnight) it will stutter and spit and I hear a knocking sound under the front driver's side floorboard which I can only assume is a backfire? I see a small crack in the exhaust manifold...but I don't know if that would cause it. It's not an everyday occurrence, but it happens enough that it's frustrating and I'd like to fix it before it becomes the norm (as I have read it can, sometimes). I'm not sure what's causing it since I'm not getting any codes for it. It goes away after I "give it some gas" for a minute or two which I realize probably isn't the best thing for it.

Any help would be greatly appreciated. I'm new to auto repair (aside from oil changes, etc.) but I really like this XJ because it's pretty straightforward when you look under the hood...and there are so many resources for fixing them.

Thanks!

aj2494

I'm not sure why that code is coming back after a CPS swap, but I have a couple ideas. First thing you should do is reset the adaptive memory. Pretty easy process that is well documented on the google machine. This should be done IMO after any major sensor change. Second, if the first doesn't work, is have it scanned at a parts store. There may be more/different codes available that way. The reason your CEL is returning after a short drive is because of the three stages for codes. Certain codes behave differently, but generally each is "stored" until it reaches a certain occurrence number, and then becomes "active". There's also a "pending" stage, but it's not important. Active codes are the only ones that cause a CEL.

You are correct in assuming that exhaust leaks get worse when the engine is hot. I wouldn't expect the symptoms to go away after giving it gas though, since the temperature of the exhaust certainly isn't dropping at that point. I'm not sure what's going on here, but is there any chance that your manifolds have been upgraded to the 99+ versions?

Radi

Yeah, Duralast sensors.... this is one that should come from Chrysler.
Flaky CPS's often act up when they heat up or cool off. That might be why yours is setting a code after it's run a while. It's hit the magic temperature.
"I can't re-start my Jeep until it cools off" is a common CPS thing for that reason.

Were you getting the code before you changed the CPS? What prompted you to change it?

#2 issue could be related to the first, or something else. I'd fix the code before deciding.
If #2 problem remains after fixing the first issue, check the fuel pressure, could be low pressure, or could be a leaky injector flooding you out.
Also check for good spark, good plug and coil wires, cap, rotor, plugs...etc.

You can rule out heat soak quickly by parking it with the hood open.

Don't worry about a minor crack in the exhaust manifold for now. Some believe it may affect the O2 sensor, but that isn't in play on a cold start.

Since you have a '96, walk over to the passenger side and give the cat converter a good kick. I bet it rattles. It shouldn't.
'96 had a problem where the cat breaks up internally and sometimes blocks the exhaust. There is a lifetime recall. If you still have the OEM cat and it's rattling, call the dealer for a free replacement.

aj2494

^This. I had a similar issue with a bricked cat on another car. It didn't click until Radi posted this. A disintegrated cat will usually run fine when it's cold, but they block everything after heating up. This, combined with that small exhaust leak, makes for a very poor hot start.

brittmeister

Thanks for the suggestions! I banged on the cat conv. with no rattle. Could it be an o2 sensor? It seems like there's some kind of gas/condensation/clog that gets in after I cut the engine off when it's hot. It happens sometimes in the morning too, with no real rhyme or reason. I reset the computer and though the jeep seems to be running a little better, and the CEL stayed off the entere 30-45 min drive to the grocery store and then home...the CEL came on the next day before I even left the little neighborhood I live in. I ordered the mopar CPS since I've read so much about the aftermarket parts failing. I'll see if that helps and in the meantime I'm going to go by AutoZone to get the codes pulled...but would you all recommend a good code reader to buy? I'd like to have one so I don't have to run to AZ every time my CEL comes on. Are the bluetooth/wifi readers you can connect your phone to on Amazon worth anything? Thanks again for your help.

Turbo X_J

Wait until you install the new CPS and erase the codes and go from there. It's really rare for a cataclysmic converter to fail. One way to really hasten the process is pretending you are throwing a rave and putting on a show for the neighborhood using that seafoam jazz. Real easy to determine if the converter is clogged using a simple vacuum gauge.

aj2494

A code reader is a code reader, they pretty much all tell you the same thing. Any one that reads OBDII codes will be fine. Just check Amazon for the more popular ones, and pick a reader with good reviews. The bluetooth ones are cool. I personally don't see that much of a need for them, but everyone I know who has one is happy with their purchase. More of a gadget than an actual tool, but you get the added benefit of probably never breaking the thing, whereas a cheap reader could break if you dropped it. As a side note, keep in mind that a cat can be too restrictive without breaking into pieces. They just generally break before anyone notices. Check it like Turbo said.

Radi

I bought this one out of curiosity, lol:

$12 including shipping plus the free version of "torque" app, it' tough to go wrong. It reads and erases codes and shows live data just fine...at least until it doesn't anymore. I don't expect long life for $10.

brittmeister

So, there has been a development...I think. A little backstory: the previous owner of my xj had removed the front driveshaft for reasons still unknown to me. The only thing she said was that it kept "falling out" which didin't really make sense to me. Anyway, this weekend I put the front driveshaft in and *poof*, no more CEL. No more code 11. I still have the spare parts handy just in case, and maybe it's because I'm new to wrenching and the like, but was the solution really that simple? Thank you all again for your suggestions!

brittmeister

And thanks Radi for the suggestion. I think I found one similar to that I've ordered and I'm gonna try that and hope it works! Amazon, ftw.

aj2494

This is weird. I have absolutely no clue why that fixed it unless you just bumped something that was loose, but you weren't really near the CPS that much. Drive it and consider yourself lucky? I don't know what else you could do.