1999 Saturn SL2 Engine Stalls

What is the atct sensor?Never heard of that before. Do u mean the coolant temp sensor?Have u had the codes read yet?If not go see what codes u have and bring the codes back to me the numbers of them. Let me know what u find.

If u don't live in California u can go to a auto parts store like autozone let me know what codes u have.

Ok no codes that was no help.U said it runs ok when it's warmed up so it's not a exhaust problem because those usually happen or get worse when the engine is hotter. When the car runs 5 mins and stalls and doesn't Start does it just turn over the engine and not try to start or does it try to start but doesn't fire up?When u changed the coolant temp sensor did u check the connector to see if it's corroded if it is u will have to replace it. It will cause a miss reading of engine temp back to the computer. Pretty common for them to corrod and do that. Let me know what u find.

It's really hard to say what it is because it happens for such a short time when its cold then it runs fine when it's hot. That is usually caused by the coolant temp sensor flooding the engine when it's cold.I something similar with another guy who change the coolant sensor and the car still ran bad. Turned out he got a defective new coolant from the store he got a differnt one and the car ran great something to keep in mind. Another thing that sucks is u can't see the readings on a scan tool of all the values of what the temp sensor is showing compared to actual temp. What the rpm is reading when trying to start cold u may have a crank sensor going bad and loosing rpm signal they don't set codes usually when they go bad. They do all kinds of differnt fail times I have seen them go fail at all differnt times even when cold.I was doing a tune up one time on a guys car and when I was done the car wouldn't start was puzzled they didn't mention this problem found out it was a bad crank sensor that had been giving them trouble for months. Also doubt it's this but we don't know what fuel pressure is when this is happening ethier. If we could see what the coolant temp sensor was reading we could say if that was a issue or what the rpms were doing if the crank sensor was doing. What I usually recomend on the crank sensor is when the car stops running and won't start to check for spark if it doesn't spark for a period of time then remove the crank sensor and give it a ohm check and see what value it reads. They usually read open when they fail no value. Did u ever take ur spark plug wires off the coils if u did are u sure u got the wire order correct when u did that. Does it run any differnt at all since u changed the coolant temp sensor. Was ur old coolant temp sensor cracked. Is ur new coolant temp sensor plastic tip or brass tipped. Do u still have ur old coolant temp sensor to try to see if it runs any different then ur new one. Let me know.

I honestly doubt it's the fuel filter without doing a fuel pressure test can't tell for sure. If the filter hasn't been changed it should be though they get changed every 100,000 miles and betime it gets to 100,000 miles they get pretty restricted. They also have the fuel pressure regulator in them so when they go bad they affect fuel pressure. There expensive too average price is like 75 but I got mine at autozone for my 99 sl2 for 30 which is the cheapest I have seen. Sorry we couldn't figure this out together but in ur case with a fuel gauge or atleast a scan tool we could read engine it makes it hard. Let me know what u find though.