Toyota Decelerates Suddenly

I have a 2005 Toyota Corolla with 312,000 miles. I was driving in extreme desert heat, uphill, ac off, and the car continuously stopped. Gauge did not show overheating. Engine light has been on because of the catalytic converter/exhaust system. Got some repairs. Now, it’s doing what it originally did. With my foot on the gas pedal, driving along smoothly, suddenly it feels like I’ve just braked – chugs a couple of times like it’s going to stop, slows, then goes back to normal for a while. Continually doing that. Especially when it is very hot outside. Already had the ECU replacement from the recall.

Does it stall with a full fuel tank? I ask because fuel pumps are located inside the tank and they are cooled by the fuel that surrounds them. The fuel pump could be not doing its job since it is overheating. If you have a full fuel tank, that’s less likely to happen so could buy you a clue as to what’s going on.

It, of course, could be many other things but driving around with a topped off tank for a while to see if the problem goes away is a cheap way of diagnosing this problem.

A couple of times it was about 3/4 full. This last time maybe over 1/2. Thanks for the suggestion. I’ll top it off and try.

Exhaust restrictions, faulty O2 sensors might cause this symptom. But those would usually turn on the CEL, and I’m assuming it is not on now, after you fixed the prior exhaust/cat problem. One question, if you replaced the cat, where did you get the replacement? There’s been some reports of non-OEM certified aftermarket cats causing problems within a few hundred miles of installation.

A dirty air filter could cause this too. Ignition system problems also, and it is common for those to be heat related. Again, usually those would turn on the CEL. Is all the routine maintenance up to date? If not, what’s behind schedule?

Fuel pressure problems should be considered also. Fuel pump, fuel pressure regulator, fuel filter. Might be a good idea to have the fuel pressure at the rail measured.

If you car has the variable valve timing, sometime it can get gummed up with oil sludge, especially if the oil changes have sometimes been deferred, or a non-recommended oil is used.

If all else fails, you may need to find a Toyota expert with the Toyota scan tool to do this diagnosis properly. Best of luck.

Thank you both! It started again leaving Death Valley at 117 degrees going the route to Death Valley Junction. Because of the catalytic converter making things better, I could clearly hear and feel the stall. It would almost stop, but I kept pushing it thinking when I got to the top of the hill, it would stop. NOT! It kept up on the flat. It was the fuel pump! Since then, $800 later, I’m doing ok. No problems. When I say I hate this Toyota they ask me how many miles. I say 314,000…then I feel really stupid. The 92 Honda with over 400,000 mi is purring better than the Toyota. How did I get so lucky? Thank you both very much. You basically had it right!

Glad you got the old beast fixed. 314K of your Toyota, and 400 K on your Honda. Terrific! Best of luck in passing the 500K mark on both of them @DrBonnie .