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Help! 2003 ford taurus ruff idle

In need of some help. I recently replaced my thermostat and housing, battery out of car for 1 day. After putting everything back together the car runs extremely ruff, brakes not working, no engine codes as of yet afraid to run it to long. i have only own the car for less than a year but i know it was well maintained. 24v dohc 6c 3.0… any help would be greatly appreciated.

It may be that the computer needs a little time to re-learn the idle parameters. When you disconnected the battery, it lost that info, got erased. Since you’ve done some work on the cooling system, make sure the coolant level is correct , not just in the overflow bottle, but in the radiator too. And keep an eye on the dash temp gauge to make sure it isn’t overheating. The problem with the brakes may be that you aren’t developing enough vacuum to power the brake booster. Presumably that could happen if the engine were not idling well. Try pushing on the gas pedal to raise the idle rpm temporarily, see if that corrects the brake problem. If not you may have accidentally disconnected the brake booster vacuum hose, which would cause both no brake and poor idle. That hose goes from the intake manifold to the brake booster and is a thick sturdy rubber or plastic hose. Make sure it is in place and isn’t leaking.

Great thanks! Should i let the car idle? It sure seems to be a vacuum issue. So far i haven’t let the car run to long because of the very ruff idle was alittle concerned. The brake booster vacuum hose is it a smaller hose in diameter?

On my Corolla anyway, it is a pretty thick and sturdy hose. Maybe 3/8 inch or 7/16 inch diameter. It takes a lot of vacuum to power the brake booster, so it needs a big hose. Suggest to do a visual check of the entire vacuum system, b/c if something else is leaking vacuum, you’d get both those symptoms too. If you can’t see anything wrong, then start it up and measure the intake manifold vacuum at idle. It should be in the 17-21 inch range, and hold steady at idle.

You didn’t remove any spark plug/coil connections when doing the thermostat job, right? Connecting those in the wrong order could cause this.

No only the thermostat and the housing which has 4 hoses going into it, as well as a sensor. Could a bad sensor cause this problem? I ran the heater and still not blowing out hot air after the replacement, so I’m guessing its got to be bad.

If you aren’t getting heat, you have air in the system after opening up the cooling system. You need to purge the air first. Then re-check your work for vacuum hoses off. Rough idle can be caused by the computer having to re-learn its settings after disconnecting the battery but if you screwed something up like plug wires or something causing a misfire, that could impact the cat. Hard to tell from cyber space but it appears you are not clearly thinking this through.

This is why you should take photos of the part you work on before you start. You can be sure you put the vacuum hoses on right. Also, it’s possible the thermostat is in upside down, but probably not. You definitely have to burp the air out of the cooling system.

thanks for the reply. none of the wires were removed. in this car the thermostat housing is like none i have ever seen. none of the auto stores around even carried the replacement housing. ford had one but for $277 so i got one from a junk yard. the thermostat goes into a housing unit w 4 hoses going into it. not sure how to think it thru i thought this would be a simple thermostat replacement and has turned into quite abit more.

Thanks! How do i go about that? I did take some photos and everything looks ok.

Burping the air out of the lines?

Side note, I misspell brakes, breaks occasionally, but ruff idle vs rough idle cracks me up,

Hee hee. Take a bite out of crime. They probably put the sign through spell check and it came out OK.

1 Like

got your attention…hopefully this isnt all you do on this site and you actually add some value.

Only when I think I have a real answer to the problem presented, sure i could say the computer needs to relearn, sure I could say the new thermostat is stuck open, sure I could say you might have broken or disconnected a vacuum hose, No engine codes, sure I could say I think your fuel pump has failed, my final answer, fuel pump. (ps did you ever change the fuel filter?) Pretty snarky for a newby responding to a guy who has been here since, oh you look it up. Was adding humor, if that is ok about ruff

Barky thanks for your input! Sorry. By the way i love the word snarky. The reason for “ruff” my golden retriever was barking while writing this and my son thought it would be funny to put that in. This thermostat replacement has turn into a nightmare.Appreciate your help!!

If the heater worked before the t-stat replacement, most likely the problem lies with that job, not the heater. Either

  • air remaining in the cooling system
  • new t-stat is faulty
  • t-state is installed backwards (a not uncommon thing that we hear here)

The heater is one of the lowest points in the cooling system, and if there’s an air bubble in the coolant line going from the engine down to the heater, the pump often isn’t able to present enough force to push that air bubble down far enough so it moves through the heater core, thereby blocking the heater core of its coolant flow. It take a lot of force, more than you might think, to push an air bubble downward in water. Have you ever tried to push an inflated rubber ball under water at the pool? It depends on the specific design, but on many cars a diy’er can get the air out of the coolant by elevating the front wheels (like on a ramp), opening the radiator cap, and idling the engine until it reaches operating temperature and the thermostat opens.

George again thanks for your help! in this model and year 24v dohc 3.0l no rad cap the water pump is ran by a seperate belt not the serp belt. t-stat can only go into the housing unit one way. could a bad water pump cause the engine to run so rough as if there is little fluid getting to the engine 2 there is a fuel shut off switch i just discovered in the trunk researching how it works may be an issue, how do you get the air out of the line other than ramping it and no radiator cap. thanks.

It may not have a radiator cap, but it must have some kind of spring loaded valve to set the cooling system pressure, just not on the radiator. You have a some kind of shop manual right? At least a Haynes or Chilton I presume. It should say in those where that function is located, and should provide the procedure to get the air out of the cooling system too. On some cars this can be pretty complicated, but I doubt it is very complicated for a Ford Taurus.

The switch you found in the trunk, I think what that does is shut off the fuel pump if you get into an accident. It triggers if it feels a big pump presumably. Same as when you play pinball and you push the table too hard and it tilts the game and shuts it off. A bad water pump wouldn’t normally cause rough running, but if the engine is overheating b/c the water pump is bad, that certainly would. But you have a dashboard engine coolant temperature gauge right? So you can tell if the engine is overheating just by looking at that gauge.

In your OP you say the problem is the engine runs poorly and you have no brakes. Changing the thermostat wouldn’t cause both those symptoms to occur at the same time in any way I can think of. Unless you inadvertently disconnected something or such as that. Of course it could all be coincidence, and the thermostat job has nothing to do with the new symptoms, which would have appeared anyway. But those symptoms are consistent with a vacuum system problem or brake booster problem , so suggest you focus there rather than the water pump as long as the dash gauges are normal. .

Bring the engine speed up to 3000 RPMs for 15 seconds, coolant will be pushed through the heater core. I don’t do that in the shop, it pollutes the air, coolant begins flowing through he heater core as soon as I pull onto the road and accelerate. After the engine cools for 30 minutes top off the cooling system.

no manual just the internet. the reason i brought up the fuel switch is because it is pressed in but yet the car will still start and idle but very rough almost to the point of dying. the car runs in this manor even if cold. every video or write up is not like my type of car. it sounds like air in the cooling line can cause the rough idling.