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2005 Pontiac Montana loses power, then can’t exceed 30-40 mph

When this vehicle overheats, I lose power and it will only go 30 - 40 mph. I know you are going yell at me for not pulling over and investigating why the overheat problem but I will offer you the following:

  1. 200,000 miles on engine. Lots of little problems that I refuse to attend to. I am tired of this vehicle, but it has served me well for many years.
  2. I had problems with a freeze plug but $30 worth of bars leak helped.
  3. I m trying to get one more winter out of this vehicle and this is my 3rd winter using this tactic.

Now for more info. After the car loses power, I drive for approx 5 more minutes and it regains the prior speed. When I do check the fluids, the radiator is full so low anti-freeze is not the problem. Perhaps with all the Bars Leak in it, other portions of the cooling system are plugged.

My question is not how to keep this vehicle running (because I do not care when it quits for good), I want to know why the lose of power with the overheating situation . It usually take awhile for this to happen after I notice the warning light coming on.

My GUESS is it is going into a fail safe mode to prevent destroying the engine.

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montana has 3.4. no leaks now. coolant level is good. motor is hot. fans are running? temp gauge says hot? perhaps flush radiator? do both upper/lower hoses feel hot?

Take it to a junkyard now and stop the craziness.

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Agree with @Purebred, it is going into limp-home mode. The only solution is to Drive it 'til it pops… won’t be long now. You’ve clogged it up so badly with stop leak, there is no fixing it, IMHO.

Does the check engine light turn on? Any diagnostic codes in the computer’s memory?

An overheated engine could lose power b/c the pistons/bores are warping and sticking, but it doesn’t appear that’s the problem given what you say. If it’s caused by the computer going into limp mode (definitely a possibility) there should be some diagnostic codes stored. That’s where I’d check first.

Otherwise, poor engine power can be

  • restricted air intake
  • restricted exhaust or clogged cat
  • problematic fuel pressure
  • ignition system problems

For the latter, if you want to make a guess of a part to replace, replace the crank position sensor. Those often show heat related failures. When that part fails you often get misfires or misfire codes.

George, the OP said he’s done with the car. He doesn’t intend on fixing it. He should simply junk it now.