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1995 Geo Prism stops moving every 50 miles

I was driving back from college for Spring Break on the I-80 when all of a sudden, about 50 miles out, the car starts bucking and losing speed and within a minute stopped moving entirely. The dashboard showed no indicator lights, and oil and transmission fluid seemed fine and there were no leaks of any kind coming from under the car. A highway patrol office stopped to help eventually, and advised me to drive so he could see the problem first hand. To my surprise, the car worked perfectly. At this point, I simply drove back to my college town to get the car fixed, as I didn’t want to risk driving 300 miles with a problematic car. The mechanic said it was because my catalytic converter was old and clogged up and switched it out for a total of $325. Unfortunately, about 60 miles of driving, the exact same thing happened. This time I drove all the way home, simply letting the car rest for 30 minutes every time it didn’t want to move anymore.

So two questions: Obviously, what is wrong with the car? And 2, how much of a refund is appropriated to ask of the mechanic who clearly had no idea what he was talking about?

If you need me to detail anything in particular, I’ll be happy to say as much as I can.

Well, you got a new Cat and it went 10 miles farther. Couldn’t resist. This does not mean that the mechanic wasn’t at least skirting the correct issue. Unfortunately, college student bank accounts and old cars with fixes don’t mix. It’s a Toyota so you do have more options then just a Chevy dealer. Until you get it properly diagnosed elsewhere, it may be tough to “ask” for anything back.

Sounds like a clogged fuel filter or failing fuel pump to me. The symptoms most closely match the fuel filter being clogged. When was the last time it was changed (date and mileage)?

Just because the car acts the same way doesn’t mean that the converter didn’t need to be replaced. You might go back to the mechanic, explain what happened and ask if s/he can explain the basis for diagnosis.

As bloody_knuckles noted, it does act like a fuel supply issue. While someone should just change out the fuel filter & take a careful look at fuel pressure under load, you might remove the gas cap and go for a long drive to see what happens.

Another possibility is overheating ignition components. E.g. an overheated coil that breaks down after a while. I’m much less inclined to go with this kind of idea since this would be more likely to show up after having stopped and sat for a while. I.e. this kind of thing would tend to get worse when you stopped to let it “rest”

I’ll switch out the fuel filter and see what happens. My dad says he can’t remember the last time he switched filters, so it’s probably been quite a few years.

I’d put a fuel pressure gauge on it first - check it under load. Then change to fuel filter and check it again. This will tell you whether the new filter makes any difference and will also tell you if the pump itself is suspect.

Your gas tank breaths out through a charcoal filter (bed) when it expands due to warming or due to agitation. Agitated fluid takes more space. The charcoal catches the hydrocarbon molecules, which are then ingested and burned via a “purge valve” when you start your engine.

It breaths in through the same filter when it contracts and when gas is pumped out by the pump.

If the charcoal gets saturated with fuel, it can hinder the ability to breath in, and when the pump moves gasoline out to the engine a vacuum can develop.It’s hard to breath through a fluid-soaked filter.That can make it difficult for the pump to supply fuel at the needed pressure, and can lead to premature pump failure. The vacuum can dissipate by itself with a short rest, depending on how saturated the charcoal is.

On some vehicles saturation can happen from “topping off” the tank after the pump handle shuts off. If you do this, I recommend discomtinuing the practice.

…and all of what mountainbike just so eloquently laid out is why I said to try a drive with the gas cap removed (or at least loose. So now I’m curious as to whether or not that’s been tried. If can’t “fix” anything - its just a simple “diagnostic.”

So we took the car to CarX today to get it diagnosed. They basically came back empty handed. They said they checked the fuel pressure and the fuel lines and they checked out and the fuel filter didn’t look very old either. The only possibility they came up with was that the battery needed to be replaced, but that made no sense to us because the car wouldn’t start if the battery was bad. I’ll take it to a different mechanic tomorrow, but in the mean time any other possibilities anyone can think of?

Yes. Drive around with the gas cap off or what? If they think this would have shown during a fuel pressure check, then I have to ask if they subjected the car to the equivalent of a 50 mile drive while watching the fuel pressure. You can do a static key on engine off check the fuel pressure which tells you a little bit. You can do an engine running, at idle check of fuel pressure and that tells you a little more. Or you can get the car under the load conditions that produce the problem and see if that tells you even more.

I’m not saying that’s it. But its about the easiest thing to rule out.

Plus a Fuel Filter can “LOOK” clean on the outside and be full-o-crap on the inside… Its cheap and should be done any way…