I am wondering what it means when a tire is "cupped." As in, "One of your tire shows serious cupping." I had the tires rotated and balanced, and the mechanic said nothing was seriously wrong, but what exactly should I watch out for? Do I have a problem with the axles or the suspension? Something else? Any suggestions welcome for this one - I hope it isn't something I am doing to my vehicle.
By the way, when I had the "Check engine" light come on last year and took it through emissions inspection anyway and it failed inspection, my mechanic said that the computerized system was resetting itself and that I should have waited until the light went off before taking it through emissions inspection. Correct?

Tire cupping - Suspension -- specifically, ball joints. The axles MAY by a culprit; however, if you run through an alignment to they should check for ball joint play on the front. Front cupping can be balance; but more likely ball joint play.

Now, one check for alignment will also determine if you have and axle problem. Mostly, that is performed on the front as tat is where the most likely wear is experienced.

If your cupping is on the rear, there is a potential for the rear axle to be bent. The same gage check used on the front can be used on the rear to determine if the axle is bent.

IMHO, most mechanics will to the minimum of balancing and rotating tires. Few have an alignment rack to check for axle and/or ball joint issues.

On your other issue, if the computerized system is resetting itself, something is wrong. One or more sensors could be questionable.

Doing an emissions check while a check engine light is on is not a good move. It is a sure sign of failure pending....

Cupping is common from improperly balanced tores. Specially common with tire/wheel combos from small dealers that don't have the proper balancing equipment.
I always use either the Jeep dealer or a specialized name brand tire company for my balances.
A realy good original balance and rotated tires should last the lifetime of the tire.
Cupping from alignment can occur from axles way out of alignment.
It does take a while for the computer to reset itself.. Sometimes a month or more.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Thanks, John and Big Jim. Well, the problem is in the front so I should start there. It sounds like it could be an expensive problem and I have a feeling I probably caused it because, even though I bought the Jeep used in 2007, it really looked like it had never been driven anywhere and I had it checked by our local mechanic as soon as I bought it. On the other hand, it wasn't checked by a Jeep specialist. So I can't do a wait and see with this one?

The sensor issue seems to have gone away. Big Jim, I did ask about this one a while back and you had some fun with oxy sensors. I actually did go to the store and find them, I think someone posted pictures of them to help me out. I never took the next step and bought any, though.

Start with balancing the tires followed by an alignment.

Ball joints do wear; especially with constant pounding in potholes.

Also check the shocks.

Many times you will notice a vibration in the steering wheel at high speed that indicates a potential front-end problem.

If the tire is severely cupped, you might consider swapping it with the spare or replacing it. It probably is out of balance and the shock absorber is bad or weak at that position. If you've ever driven next to a vehicle with a bad balance and a bad shock and seen the wheel bouncing up and down, this is what causes the cupping.

The check engine light indicated a failure in the emissions system, not that it's "resetting itself"! If the light is off now, and you did not do any repairs, most likely you had a loose gas cap that caused a leak in the evaporative emissions system ('96+ Jeeps). This fault will take at least two good trips to turn the light off, but the code will still stay in the PCM for a long time. Depending on the year Jeep TJ you have, you can cycle the key three times from the off to the run position, leaving it in the run position the last time and the code will appear in the odometer. If your Jeep has this feature, it will either show a code starting with a P and four numbers, (ie: P0456) or it will say NoCodes. Some early models will only flash the check engine light and by counting the flashes you can read the codes. Others will not give any flash codes and you will need a scan tool to verify that there are none in stored status.

In Kalifornia, a stored emissions code will cause you to fail a smog test!

If I was you I would take your jeep to a local auto repair shop and have them pull codes for you. If you have no codes and no engine light you are good. You may not have an engine light on but still have some stored codes and depending on those codes you may want to look into having some repairs made.

Most of the time you need to have the codes cleared before you go to emissions. In alot of newer codes though you can't clear codes and go right through emissions because your computer will throw a P1000 code which means your computer hasn't had enough time to check for problems. You can reset your computer yourself by removing your positive battery wire from the battery and thouching it to the negative side of the battery for five seconds. Then drive the jeep for a full tank of gas to see if the light will come back on.

If your computer is resetting itself there is an issue that needs to be addressed. It should not do that. Too bad you aren't local, I would help you out for free pulling codes and such.

It's funny, I never noticed anything bouncing or pulling. Usually I notice everything, and I go a lot by listening. But there must be something going on with the front end. I do a lot of driving on Interstate 95 up and down Maryland and run into quite a few bumps and potholes, so I am blaming those for the problem, ha.
The Jeep computer thing is becoming very interesting. I do have something funny also with the gas cap. It does not seem to close very tightly and when I pump the gas the automatic shutoff doesn't work, not enough seal I suppose. So I have learned to listen and when the tank is just about full I shut off the gas so that I don't have the runover. So now I may try look into some of your tips, MartySoCal.

Well, Arizona isn't that far.

So maybe I can try the battery solution. It seems to me, though, that some folks (like my mechanic) think the computer resetting is a normal thing, and others think it is a problem. Can there be a normal resetting or not? I think the computers in general are a bit of a problem.

Try a new gas cap...