Dear Tom and Ray:
I have a 1997 Jeep Wrangler, 4-cylinder, automatic, with 51,000 miles. It runs like new until you go over 60 mph for about 10 or 15 minutes. At that point, it seems to not be getting fuel. It sputters like it is going to die. To keep it from shutting off, I have to keep tapping the gas pedal as I come to a stop, or it will stall. I recently tried some fuel-injector additive, thinking that might help. It didn't. I've also tried using 91-octane fuel to see if that made a difference. It didn't. The fuel filter was changed a year ago. What else should I look at? Thanks.
RAY: The 2015 Wranglers?
TOM: My first thought is that if it seems like it isn't getting fuel ... maybe it isn't getting fuel? Maybe your fuel pump is weak.
RAY: That's easy to test. Your mechanic can put a gauge right on the fuel rail to see if the pump is delivering enough fuel pressure.
TOM: Another possibility is a clogged catalytic converter. If the exhaust can't get out of the cylinders when you're running at high speeds, then your fresh charge of gasoline and air can't come into the cylinders. That could cause the engine to stall. And that would tend to rear its ugly head after you've driven it for a while.
RAY: Or it could be unrelated to the fuel system. It could be your spark that's failing. A bad crank-angle sensor could interrupt the spark, as could a failure of any part of the secondary ignition system, like the distributor cap, rotor, coil wire or coil.
TOM: So you know what you really need, Phil? A mechanic.
RAY: Yeah. You're guessing. But the guessing is going to start getting expensive soon. So find someone who can actually test these parts for you, and you'll have a better chance of homing in on the problem. Good luck.