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No answers in the MWC section, can anyone help over here??

xCOYOTEx

NAXJA Forum User
Location
Indianapolis, IN
OK, I am a little confused right now. Gave my motor the Seafoam treatment today. Pulled the Vacuum line off the Power brake booster and poured the seafoam into that hose. Now on most cars I have had, pulling the vacuum line would normally make the idle drop and the car want to die. But on the Jeep, I had the total opposite effect. It revved up and ran a little bit better. So is my memory foggy, or do I have another problem? I have put new plugs in the jeep for a small miss, but have not replaced wires, cap and rotor yet. The Seafoam seems to have helped a little bit, but it is still there. It also gives a small backfire from time to time when shifting from 2nd to 3rd gear. And as I have said in a previous post, I have some lifter/rocker noise. Plan to replace cap/rotor/wires, timing chain,give it a oil change plus bottom end gaskets/seals. (Well maybe not the rear main, it seems to be the only one not leaking. But front seal definitely needs replaced.) Also will pull valve cover and try to adjust the valves. But for right now, my biggest question is why did the motor rev up instead of stumble? Motor is the 2.5 4 cyl with the 5 speed. Thanks!
 
If the vacuum leak is not a large one, like though a metered orfice, the immediate affect is an increase in RPM due to a slightly leaner mixture. This implies that the original mixture is a bit rich.
 
So on a fuel injected motor, what causes a rich condition?

A bad O2 sensor could cause a rich mix, on a renix 4.0 a bad coolant temp sensor could also but on your 4 cyl., no other clue.

Every time I have Seafoamed my Jeeps, they have almost died when I sucked the stuff in.
 
Well I am gonna take it to the Vato Zone and see what pops up when it is plugged into the computer. I will check the O2 sensor and see what it looks like as well, make sure there are no broken wires or whatnot. I at least have a couple avenues to check. Thanks for the feedback so far.
 
Ok, OBD 1 can not be plugged in to the computer. Anyone know how to get the codes?? Also, I drove the Jeep today without the vacuum line hooked to the brake booster. Ran way better, but still has a miss. And now for what is making me wonder if I didnt screw myself on this Jeep. When the engine is running and I pull the oil cap off, it is almost like the exhaust is coming from the valve cover. I get a puff of air coming out where the oil cap was. WTF?? Bad valve? Stuck Valve? I have NEVER had that problem, nor have I heard of this happening. So what would cause that??
 
There's a sequence of key-on, key-off that should flash the CEL light to get the codes. Don't remember the trick off the top of my head, though.

Is your crankcase getting pressurized? Check the PCV valves on top of the valve cover.
 
It's supposed to idle up when the vacuum line is removed because you're basically just letting more air into the engine, like opening the throttle. Maybe you should clean the throttle body, maybe it's covered in junk. Is there a lot of air blowing out of the valve cover while it's running? Maybe you have blow-by caused by bad piston rings. You can do a compression check to verify that. And I thought the lifters would be nonajustable on the 4 bangers as well. Maybe throw some marvel mystery oil into crankcase to free them up. And than change the oil.
 
For OBDI: Key on, then off, then on, then off, then on and leave it. Engine is not running. The Check Engine Light should now begin sending two-digit codes in the form of flashes. A "5-5" will always occur to signal the end of the sequence. Some will flash the "1-2" code indicating a recent battery disconnect even if you haven't done it. Ignore these, and mark down all others. You can find a list of the codes on line, or repost here for help.

I regularly ran top engine cleaner into my 95 to conquer a recurring knock. Never had to do so with the 99, for some reason, in something around 275 thousand miles. I could never quite make the 95 stall. It's a very forgiving system.

You'll get some blowby even in a fairly healthy old engine, but yours sounds like a bit more. A compression check would probably be a good idea. You should also make sure that there is no buildup of crud in the little vacuum line that powers the crankcase ventilation. Oil junk builds up and eventually fouls up the ventilation. There's no PCV valve as such, and the whole system operates by a fairly delicate balance (and probably a little bit of black magic).
 
Will check all that this weekend. Thanks everyone for the help so far. I really hope I dont have to rebuild the motor, as I was planning a 4.0 swap later next year. Guess I will try the marvels treatment and a little prayer. Will also remove valve cover and make sure it is all cleaned out. Thanks again!!
 
OK, I am a little confused right now. Gave my motor the Seafoam treatment today. Pulled the Vacuum line off the Power brake booster and poured the seafoam into that hose. Now on most cars I have had, pulling the vacuum line would normally make the idle drop and the car want to die.
Don't know what else you have worked on but on a speed density fuel system (MAP based) it will take into account the extra air and adjust fuel accordingly. The opposite is true on a mass air system. Not a problem
I have put new plugs in the jeep for a small miss, but have not replaced wires, cap and rotor yet.
Depending on how many miles I would replace those as well. Also consider the fuel filter and air filter.
The Seafoam seems to have helped a little bit, but it is still there. It also gives a small backfire from time to time when shifting from 2nd to 3rd gear.
i would take a look at the distributor indexing and maybe the MAP sensor. TPS is also a common suspect.
Also will pull valve cover and try to adjust the valves.
Your valve train is non adjustable. Best you can do is give a good hard, high reving, hot run to clean off the valves and remove varnish from the lifters.
 
OK. Been having another problem with the Jeep. Driving to work the Jeep would sputter then would run normal, kinda acted like the key was turned on and off sometimes. Then it stopped doing that and was running fine, then died on me after it sputtered and ran rough before finally quitting. Then i went back to it later and it started right up. Got it home, changed cap/rotor/wires/coil and took it for a test drive. Ran better but still had a small miss that I have been fighting for a little while. But then it quit again. So I let it cool and it refired but ran rough. So questions are:1) Crank positioning sensor cause this problem? I got codes 11,12,14,54,and55. 2)if it is the CPS, could that cause the miss I am fighting? 3) am hearing that the CPS is a hard item to get through Mopar. Is that true, and if it is does anyone think NAPA would have a decent part or is there an aftermarket CPS that someone would suggest?
 
Typically CPS issues show themselves by not allowing the vehicle to start... at all. Rough running is usually related to O2 sensor and fuel map issues, however TPS and IAC are not above suspicion in these instances. I would start with the O2 sensor, and pull out your IAC and clean it with break cleaner, powder solvent (hoppes #9), or a combination of both. Also, if you havn't already done so, you might want to put the seafoam in the gas tank as it does a bang up job of cleaning the injectors which could also be a problem. I have never had to replace an injector because of a clog, but I do notice some gas additives do a bang up job of cleaning that system out.
 
There's a sequence of key-on, key-off that should flash the CEL light to get the codes. Don't remember the trick off the top of my head, though.

Is your crankcase getting pressurized? Check the PCV valves on top of the valve cover.

There is no PCV valve on XJs, it is a CCV tube-hose network. His rear CCV tube and orifice may be plugged and its purpose is to scrub the blow by gasses from the crank case. Very common. I suggest a new CCV tube kit, NAPA seems to keep them. Also pulling the brake booster vacuum line off added to the problem IMHO.

A bad TPS, sticky IAC, and a vacuum hose leak from the throttle body to the MAP sensor are all likely culprits now, especially the MAP sensor vac line leak for the 203 gear shift back fire!!!!!! Then the TPS is second on that same list, and last the O2 sensor or its the wires to it for the backfire.
 
OK. Been having another problem with the Jeep. Driving to work the Jeep would sputter then would run normal, kinda acted like the key was turned on and off sometimes. Then it stopped doing that and was running fine, then died on me after it sputtered and ran rough before finally quitting. Then i went back to it later and it started right up. Got it home, changed cap/rotor/wires/coil and took it for a test drive. Ran better but still had a small miss that I have been fighting for a little while. But then it quit again. So I let it cool and it refired but ran rough. So questions are:1) Crank positioning sensor cause this problem? I got codes 11,12,14,54,and55. 2)if it is the CPS, could that cause the miss I am fighting? 3) am hearing that the CPS is a hard item to get through Mopar. Is that true, and if it is does anyone think NAPA would have a decent part or is there an aftermarket CPS that someone would suggest?

Code 14: is MAP sensor voltage complaint, so the vacuum line first to the MAP, check it, then Voltages......

Code 12: Is loss of battery power, did you disconnect the battery recently, if not there is contact problem there, ground or + post

Code 11: Is loss of CPM signal!!!!

Code 54: is loss of the Distributor signal (It tells the PCM where the Camshaft is, similar to the PCM).

So many signal loss codes looks like a battery connector post-clamp problem, but be sure to check the MAP sensor vacuum line too!!!!

IIRC 11 and 55 is a begin and end message to the string, nothing more.
 
As I recall, only 55 is normal, but 12 is common sometimes even if you can find nothing wrong. However, it's always a good idea to check your battery connections, because a bad connection can cause all sorts of odd problems. Mopar fuel injection systems are notorious for running badly if the battery is not good enough to buffer the system. It's a common problem when jump starting a Jeep or similar vehicle with a dead battery. It will run but the unfiltered over-voltage will screw up the electronics.

When the distributor (cam position) sensor went bad on my 95, it sent that code, but also, when I managed to get it running enough to get home with a bad cam sensor, it sent a bad CPS code which was a red herring.
 
The 11 code is real, CPS code, out of range. Not sure why I posted two different things last time for 11, must have been tired.
 
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Ok, replaced the CPS and it runs and has not died since I replaced that. I will replace the MAP sensor and the TPS. But what is IAC? I am sure after someone posts what it is I will feel like a idiot, but that one I can not figure out. Thanks for everyones help yet again, hope to get these problems ironed out before winter. And I dont want to keep spending money on all this stuff, there is a 4 1/2 inch Zone offroad lift kit that is calling my name, along with a set of 32 BF Goodrich KM2's. That will be the spring project.
 
the IAC is the Idle Air Control

It's the other doomahickey on the trottlebody around the corner from the TPS
 
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