I am at the end of my rope

I really am ready to sell my XJ and get something that will run right with out emptying my pockets. Today was just about all I can take. Most of the problems that I have had with my Jeep have been things like rust and worn out steering parts, bad springs, shocks and brakes. I can handle all of those things, but it is the lack of power that I had in my motor today that has almost pushed me over the edge. My Jeep is a 93 XJ 4.0 AW4 with approx 138,000 miles. I doesn't burn oil, and seems to be very mechanically sound. I own a 6x8 trailer that I use to pull my 4 wheeler, and sometimes my dads as well. I love my jeep because it has plenty of power to pull this no problem. Today, I decided to take my trailer, empty, to buy some tile for my counter top. I was driving from Logan Utah to Ogden Utah, through sardine canyon for those of you who are familiar with the area. For those of you who aren't, is is just your average canyon that goes from about 4500 feet to 6500 feet and then back down. It is nothing too intense, but I have always been able to hold a constant speed of 65 with 2 atvs on the trailer in 3rd gear. Today, with the empty trailer, I was only able to hold a speed of about 40mph in 3rd gear, to go any faster, I was unable to go any faster or hold a constant speed unless it kicked down to 2nd. My temp also was on the rise, which has never happened before. The motor never missed, but it seemed to ping excessivly. I limped along at about 25 with my hazards on until I got out of the canyon. I bought a new Dist cap and rotor, some octane boost, and toped the tank off with premium gas. I carried on my way to Ogden, slowly. But on the way home, I was crossing my fingers that I would be able to make it up the canyon, but I couldn't. I went about 4 miles up the canyon and the gauges read as follows. Temp, almost redline, oil, 50 psi, volts, 9.5. I have replaced almost everything sensor wise on the engine. I am also running a APN header, Rustys cat back with the 40 series flowmaster and a cat that only has about 15,000 miles on it. I am at a loss, I checked my fuel pressure at it holds steady between 38 and 45 psi, and I also hooked up a vacuum gauge and it reads a steady 14 inHg at idle. My house sits at about 4500 feet above sea level, so I think that is a pretty good reading. I don't know what else to do. I am sorry that this post is so long, but my Jeep is sucking my bank account dry. Everytime I get one problem fixed, there is another one that comes up. Any help would be great.

Maybe your injectors are clogged. You could SeaFoam it and see if that helps.

I have run some of that in the past, though I havn't done that for a while. I have even run a can of BG44K that old man is always raveing about.

Lots of possible causes, but I had one, a no power issue, that I chased for 2.5 years on my 87 Renix. Of course it had a good one to two dozen other problems when I bought it, so they added to the confusion.

Anyway it turned out the front ECU side of my TPS was working perfectly (the side I always cheked and calibrated), but the idle to WOT range on the TCU side of my TPS was gone, The TCU thought the TPS was in idle mode all the time, so it never downshifted even at WOT, and always upshifted way too early, so it had no power.

Other than that, I would start at square one with an ohm meter and check all the sensors.

Did the rest of the Vacuum tests look OK?

38 to 45 psi for the gas sounds a little high. Do the HO's run at higher pressure than the Renix 4.0's? The older Renix ones run at 30 to 39 psi as I recall.

I do know that if the catalyst got damaged, broke loose, or got too hot and melted, it can cause your power problem. So could a head gasket leak, bad MAP sensor, maybe a bad CTS, or bad IAT sensor.

Check your catalytic converter, It might be all clogged up

If you really only have 9.5 volts, something in your charging circuit is bad. Likely your alternator. That would explain it running bad as your fuel pump is electric, along with the injectors, and ecm, ignition, blah, blah, blah......
That could also explain your temp gauge problem too, as it works off of voltage too. I'd think somewhere there is a ground strap that goes from the engine to the body, this would be a good thing to check too.

I also had a problem with my jeep just like that towing in W.V. it truned out to be the TPS all i had to do was adjust it and just like that it's fixed

Yeah, I agree with mccastlexj, if your gauge reads 9.5 volts, that means something beyond is seriously wrong... even if your alternator quits on you you should still be getting around 11-12 volts because of the battery voltage, unless of course your alternator has been shot for awhile and your battery is depleting, but then you'd notice it cranking poorly.

This may sound stupid, but check your belt; I mean, if it's slipping badly it doesn't always sound like it, and that would affect your waterpump, fan, alternator, etc which could also be leading to overheating. And check your entire charging system because like mccastlexj said, at 9.5volts nothing is going to be running correctly.

I don't believe it would be a cat as those don't just all of a sudden clog up, it's a gradual thing, unless something physically broke in there and plugged something. Ecomike had good suggestions regarding the TPS, map sensor, etc, but before you buy any new sensors, figure out why your charging system isn't reading around 14 volts.

The jeep voltage meters are notorious for lying and reading as low as 9.5 volts when the battery tests at 14 volts with the engine running, so I ignored the 9.5 volt report. Besides, He would probably have starting and idling....etc., problems if the voltage was reallly that low. Just check the battery voltage at idle, should read 13 to 14 volts depending on other loads like headlights and AC blower.

The over heating plus low power really sounds like its running too lean, and the pinging sounds like timing advance, or overheating when it should be retarded for more power. So I would test that MAP sensor (considering your altitude), check the Cat for overheat damage that can result in a blocked exhaust, overheating, and low power, and check both sides of the TPS at WOT (engine off) to make sure it still has a full sweep from idle to WOT on both sides, especially the Tranny, TCU side as it can casue low power by causing early shifting, and keep the tranny in too high a gear, thus causing low power. Lastly check the CTS and O2 sensor as they can affect fuel, A/F ratio which affects engine temperature and power

, and timing. Once again all of these can be tested with a $10 - $20 ohm meter in less than hour, except for the Cat. The cat can be tested by having some one run the rpms up to 3000 rpm and then feel the exhaust pipe velocity with your hand to see if it feels restricted. Any rattingly sound from the Cat is dead givaway it is damaged and blocking the exhaust.

Just post your test results here, or search here for prior posts of proper sensor ohm/volt test readings if you do not have them handy.

Well, I have spent most of the day trying to hunt down my problems. I checked the cat this morning before I started the Jeep. I couldn't hear anything rattling around inside. I checked the CTS, cold it was 11,000 ohms, operating temperature 800 ohms. TPS closed .738v TPS wide open 3.6v. I have also done various tests with the vacuum gauge, and the motor seems to be funning just fine, with no problems. I also took it into Autozone and had them test the battery and alternator, and the guy said that it all checked out just fine. I guess I won't pay much attention to the gauge in the dash any more. I am starting to think that the problems I am having aren't engine related. But it doesn't seem like I am having any trans slippage. I am wondering if my brakes are grabbing, but I did a little test today. I got up to 25 and shifted into Neutral and coasted 1/2 a block to the next stop sign. I didn't really slow down, maybe a couple of miles per hour before I had to stop. But I did jack the front end up and tried to spin the tires. Both front tires spun, but they didn't spin freely like I thought they should. The back tires spun freely. I am not really sure how to check the brakes, but I don't think they should grab as hard as they do. I really appreciate all the replys that I have gotten in response to my problems.

Oops

I had the same problem going over sardine pass. My alternater went out as I was passing Mantua. It would run but would not go up the canyon. I had to jump the fence and use the phone at the nearest house on the north end of Mantua. Good luck!

Your CTS numbers OK.

You said "TPS closed .738v TPS wide open 3.6v." but which side of the TPS was this, if it was the four pin Tranny side I think that range is too narrow, and thus the TPS is bad and causing annemic power, but I am basing that on the correct Renix TPS values that I know, I do not have enough data on the '93 TPS.

I had to buy a new Renix TPS just to get the idle to WOT ohms data for a new one as it was not published. Perhaps someone else has the 93 (91-95 should be the same), TPS data. Now that I think about does the 93 TPS even have two connectors???? If not, then I would suspect the 3.6 volts is about .5 to 1.0 volts too low.

I don't see how kicking down to second gear while towing in the mountains is in any way unusual. But that's just me I guess.

Maybe you should run a compression test. Even if you aren't buring oil, your piston rings could be wearing prematurely causing a power loss. Or you could have a blown head gasket or crud on your valves.

I would not trust what Autozone is saying about the alt/battery, that voltage is way too low to carry the engine electrics without some power starvation.

Get a second "proffesional" opinion on the electrical system. Check the cables and their connections as well.

xjtrailrider said:

I would not trust what Autozone is saying about the alt/battery, that voltage is way too low to carry the engine electrics without some power starvation.

Get a second "proffesional" opinion on the electrical system. Check the cables and their connections as well.

Click to expand...

I'm just throwing this out there, but would checking/changing spark plugs help?

I had a simular problem with my 91, turned out to be the cat. You said yours only has 15K on it. Just take it off

Agreed with Ecomike, and all the others who said/thought the same thing. The voltage gauge in the XJ is notorious for lying. My 89 has a voltage reading of 9-12 volts, has for 6 months now. Doesn't matter if I'm on a trail, in the field, or pounding down the freeway. A few months ago, I rigged a multimeter directly to the battery, so I could watch the actual voltage. It read good across the board.....as well as alt. checks from 4 different shops.

Bottom line?? Don't trust it...unless it drops off to 0, or spikes all the way over. If you were really charging at 9.5 volts, you would have starting/accessory issues....

Well, here is an update. I took my Jeep into a local muffler shop. I had them check out the CAT. They said it was great. Plenty of flow and good pressure. So, I think that has been ruled out. I also changed my spark plugs. I am not sure if I gapped them wrong the last time that I put them in, but the gap on them was in the range of .042 to .050. Is it possible for the gap to get out that much. The plugs were champion truck plugs and were only in for about 5000 miles. I put in Autolite platinums. Seems to run good. I checked my front brakes again. With the wheel off, I could hardly turn the rotors by hand. I took the calipers off to make sure that the binding was actually the brakes and not something else. The hub spun freely. So, I cleaned up the rotors and the part where the brake pads slide. Greased everything up good, installed new pads. The old ones were worn on a weird angle. Everything seems good. Tomorrow I will recheck everything and make sure that the front wheels still spin freely. I hope that I have found, and fixed my problems.

Edit: I gapped my new plugs at .035, and I thought that is what I gapped the old ones at.

check the fuel filter