Car shuts off when warm, white smoke from exhaust

I know, sounds like blown head gasket. However oil looks fine, no coolant leaking and coolant looks fine. It also does not overheat (that I can see, it dies first). This all started a few weeks ago. I changed spark plugs, oil and undercoated the car with primer. I did get some paint on the radiator. I also put techron in the fuel tank and changed fuel filter. The car ran fine before, now here is what is happening step for step.

Car starts fine, idle is a bit rough (it was before too) but nothing drastic. I rev car at 2500 RPM until it is warm. The thermostat stays in the middle yet I begin to see a good amount of white smoke coming from the exhaust. If I take foot off the accelerator the car will shut off at this point. If the car is not warm yet, it won’t shut off. When it does shut off, I cannot restart it even with gas pedal down. It just cranks and cranks. When I let it cool down it starts up fine and the same thing occurs. I cannot tell if the radiator fans are turning on as the car dies before they turn on (it’s cool outside). The thermostat never indicates overheating.

The entire radiator is smoking white (not from cap) but I assume that is from my paint overspray burning off. Could this be getting sucked in and stalling the car out when the car warms up enough to start burning off the paint? Could I have painted something inappropriate? What could this be? I know a decent amount about cars.

If I let the car warm up just by idling it will run until it gets warm then it stalls and again, won’t start until it cools. It seems to keep running if I keep RPMS up but right when I take foot off accelerator when warm it shuts off. Ideas?

Check your IAC and see if it is clean. Also, your temp sensor may be bad. The one that feeds the computer. If it is bad the engine will think it is still cold.

I can’t get the radiator fans to turn on, the car shuts off before they turn on but thermostat is still no higher than middle. It also seems like coolant is not circulating although the heat works fine.

Ok well the “white smoke from radiator” is just steam from spilled antifreeze. The coolant DOES seem to be flowing but I radiator fans are not turning on. The car still reads that it’s not overheating though so maybe they shouldn’t be turning on yet. Right when I don’t keep throttle at a decent rev the car cuts out and can’t be started until cooled down for 5-10 minutes (although it’s still warm as it’s only 10 minutes?). I did clean the IAC and throttle body already and checked pcv valve.

Could all of this be the crank angle sensor? I have no check engine light and no codes in code reader though.

This doesn’t make sense to me. If I keep the car throttled the engine will not die and it is not overheating yet right when I de-trottle the engine sputters and dies IF it is warm. If I rev and then idle when car is not up to temp everything is fine.

That is why i mentioned the temp sensor, not the one that feeds the gauge. When the engine is cold it is in open loop mode and when warm it is in closed loop mode. That is when the O2 sensors and the emissions all come into play.

Also, I will mention this is a 2003 hyundai accent. Wouldn’t that sensor throw a code if it went faulty?

Are you referring to ambient air temp sensor?

No. the coolant temp sensor that feeds the PCM.

Alright will check this out first. Any chances my symptoms sound like a bad engine to body ground? Maybe I painted on one and screwed up connection. It is just uncanny, the car will not start when temp on panel is mid-range. It starts fine when it cools slightly below this. Keep replies coming I appreciate this a lot.

What does the exhaust smoke smell like? Check your oil for the smell of gasoline too.

Smells normal to me… car doesn’t spit smoke when idling. I am going to replace the temp sensor tomorrow and see what happens.

To play devil’s advocate on the ECT being the culprit… when I start the car in this cold weather it begins at 1200 rpm then as it heats up drops to 750 rpm. Isn’t that what the ECT does and wouldn’t this indicate it is working?

Well I finally got it to through a code although no check engine light. P0121 which is a TPS.

White smoke out the exhaust does make one suspicious of coolant getting into the combustion chambers. A head gasket leak in other words. But not necessarily. White smoke coming from the exhaust pipe when first starting the car, especially when it is cold outside, is completely normal.

Edit: I think a rich mixture can cause white smoke too.

Since you get a code for the TPS, and that is a common thing to break on modern cars, definitely the first priority is to have it tested, or just replace it w/a new one maybe, if that is the less expensive alternative.

If that doesn’t fix the problem, my first idea when reading your post is fuel injection system contamination. I had a VW Rabbit one time and every time I replaced the fuel filter, somehow the fuel injection system got dirt and sand in it. The result was that the engine would stall and die on acceleration, especially after it was warm. My theory is that there was dirt and sand on the inflow to the fuel filter, but it didn’t cause a problem as it never went beyond the fuel filter, but somehow the dirt and sand got into the outflow line during the filter removal process. If so in your case, Techron won’t solve it. The fuel injector system, maybe just the injectors, will have to be removed, inspected, tested, and cleaned.

You might get lucky, inspect the fuel pressure regulator. If there is a hose from it running to the intake manifold, pull that hose, see if there is any fuel in side of it. There shouldn’t be. If there is, have the regulator tested, or just replace the pressure regulator.

As you suggest, the fact that the idle speed is dropping as the engine warms up is consistent with the CTS working. However, checking its resistance at ambient temp and comparing that to the chart for what it is supposed to be is an easy enough thing for a mechanic to do, so it I worthwhile doing that before considering to replace it. (Note: Many cars have two coolant temp sensors. One is just for the dash gauge. Make sure you are testing the one used by the computer.)

When I unplug the TPS and MAP sensors I get no codes. Shouldn’t I be getting a code for the MAP sensor? In any case, disconnecting them both results in the same problem, the car when warm will only run with throttle. Once I let it idle it instantly dies and will not start until temp starts to drop below middle on dash gauge, then it can be started immediately.

When I disconnect the coolant temp sensor that’s the symptom I get on my early 90’s Corolla, the car will barely idle. But the check engine light comes on immediately. Disconnecting the MAP should turn on the CEL, but it might take some time before it does. When the MAP fails, the car’s computer probably uses a default setting, so it should still run, maybe just not so good as before. You’d notice it more during acceleration. That’s when the intake manifold vacuum changes the most. I’d think disconnecting the TPS would turn on the CEL, but again it might take some time before it does. The software designers may think it is worthwhile to just be hoping it is a fluke, and will start working again.

Edit: one idea to consider, when the engine becomes warm the O2 sensors start working. Before that the engine runs in open-loop mode, that’s how cars of yesteryear worked. When the O2 sensor heats up, then the mixture is determined by the O2 sensor reading. There could be something wrong with a that, with the closed loop operation, since it seems to occur only when the engine is warm

The more I read this really sounds like vapor lock.

My impression from your posts is that it’s cold where you are. Since the engine never really warms up the exhaust, the white smoke from the tailpipe might just be normal condensation. If you’re not losing coolant and not hearing horrendous noises from the cold engine, as you would if it were drawing coolant into the cylinder, that’s probably all it is.

But the best way to find out is to do a cylinder leakdown test. And I’d recommend it. Or, alternatiely, you can get a “lab strip” that’ll detect hydrocarbons in the coolant and change color. Either test is simple, easy, and will tell you if you’re getting coolant in the chambers (if a cylinder is drawing coolant into the chamber, it’ll also be blowing hydrocarbons…exhaust gasses… into the coolant. I’m betting you do NOT have a headgasket leak, but I recommend that you check.

You might have painted something inappropriate. If overspray got drawn into the air cleaner box, some of it might get past the air cleaner and coat the mass airflow sensor. That’d definitely trash the sensor. And that would mess up your fuel metering signals.

I can confirm spray didnt go near the air intake box. Also my car does not have a MAF sensor although same point.