Car will not restart on warm or hot humid days

pontiac
grandam

#1

2004 pontiac grand am, after driving and shutting off the car, it will not restart or stalls out while waiting at traffic lights. When I try to restart the car, all I get is clicking sounds, only does this on warm or hot humid days. The dealer told me to just hold down the gas pedal and crank the engine till it restarts. I have tried the turning on the key for a minute, wait, then turn the key back off, and then to restart, but that doesn’t work either. If I wait for a good ten minutes, the car usually starts. When I turn on the key I do hear the fuel pump kick in. I have replaced the fuel regulator, ignition switch, keys, computer chip in the ignition system, battery, and starter- twice. I have heard that it could be a crankshaft sensor but would like to know if anyone has any different ideas ? No codes are showing up when this happens. Thanks for your help.


#2

I was thinking coil/spark issues until you said you get a clicking sound. Clarify please. When it stalls your starter doesn’t work? That would indicate a battery/alternator/cable/ground problem.


#3
When I try to restart the car, all I get is clicking sounds
,

OP, your posting is a little unclear. You say after turning it off, it stalls out while waiting at lights. Do you mean after it has been sitting, then you start it, if it starts, it isn’t idling correctly and stalls out?

Also, those clicking sounds when you try to restart, is the engine cranking over, but it won’t catch and start? Or is the engine not even cranking at all?

You are right that given what people say here, both crank and cam sensors can be intolerant of heat build-up, and replacing one or the other can sometimes solve hot-soak problems.


#4

Not restarting because all that it does when you turn the key is click - and stalling out at lights are two entirely different thing. And no one can really help you until you clarify whether or not the “will not restart” is because there is only clicking rather than the engine actually turning over.


#5

I can drive 3 miles or longer and shut the car off, when I try to restart the car, it turns over but it won’t start up,wait 10 minutes or more and it will usually start back up.starter turns over but nothing else happens. In traffic, on a hot day, it just shuts itself off, if I wait 10 minutes, it always starts back up. all electrical connections and spark has been checked out. its only on hot humid days when it takes place.


#6

You need to check the fuel pressure. And turning the key on for a minute doesn’t do anything. The fuel pump only runs a few seconds either way. If the principle is trying to make sure the system is up to pressure you have to go on/pause - off - on/pause - off - on/pause - off etc. Do a static check of fuel pressure. Then check it under load. Then check its bleed-off and rise on a hit shut down and attempted restart.


#7

I’m thinking coil is going south when it heats up. Gonna have to check for spark though when it won’t start.


#8

If I understand the last description correctly, the starter motor is working normally but the engine won’t fire. I too am inclined to suspect a heat sensitivity problem. On a 10 year old Pontiac I’d suspect the coil pack or the igniter, only because they’re the most common items to become heat sensitive.


#9

A crank position sensor would be my guess.


#10

warm 70 degrees today in iowa,got off work today, drove 1 mile, shut car off for a few minutes, went to restart, won’t fire up, same thing again. the dealer says to fix my car, it just has to quit altogether and then maybe they can figure it out. a local mechanic installed a fuel pressure gauge and fuel pressure was all right. according to the pontiac website, there are a lot of these issues with these models. thank you for all the responses.


#11

It would seem that the dealer doesn’t want to be bothered.

If I understand correctly, you’ve found an independent and the car is there now? There’s nothing the dealer could do that an independent cannot. One thing they can do is put an analyzer on the engine and see what shows up when you try to start it. I’m guessing that you’re on good hands now. Checking the fuel pressure is a valid place to start.


#12

Was the fuel pressure just given a static test? Or tested under load?

In any case, hot and humid (or warm and humid) does point to a problem with an electrical component such as a crank position sensor or coils going south as mentioned by others above. GMs are particularly prone to the CkPS failures.

Heat and moisture can be “artificially” induced to test specific components. A heat gun and spritzer bottle of water can work wonders in pinpointing this kind of problem.

Either way, a check of anything while stuff is working right won’t tell you much. So if you want people to help you narrow stuff down, don’t just vaguely refer to things having been “checked.” Checked how, and under what conditions.

Here’s another one - loosen or remove your gas cap and see if that does anything. This will eventually set an error code, but that can just be cleared.


#13

mechanic checked the fuel pressure and can’t find anything wrong in that area. the thing that’s puzzling me is, why does holding down the gas pedal allow the car to start? on hot humid days, this is the only way to get the car started. winter time, no problem at all. this is what the dealer recommended in doing, instead of fixing the car. changing the ignition switch has stopped the car from stalling in traffic but for 700 bucks, i was hoping it would have taken care of the no-start problem. thanks


#14

I think ok4550 is likely correct, bad crank position sensor. These can be very temperamental in heat. That’s why the problem only shows up in warm weather.

It starts again when the crank position sensor cools off a little. By that time, you’ve flooded the engine by cranking it over and over. Flooring the gas pedal just clears the flooding. That’s why flooring the gas pedal helps restart the engine.


#15

I think I’m wrong. The new wrinkle is the starting with the pedal depressed. That often points to a vacuum leak or Idle Air Control valve problem; usually the latter.


#16

I have nothing to add to the possible causes, but for $700 he SHOULD have also fixed the no start problem! You need a new mechanic.


#17

@dave290, If you do get it started by holding the gas pedal down some, does it start up and run pretty smoothly? Or does it do some choking and sputtering? If the former it is how a bad IAC behaves, as noted. If the latter, it probably sends you back to fuel.

I was not kidding when I said that hot/humid can be artificially induced on various components, including the IAC. At the very least I would clean it.

You have also said twice now that your mechanic checked the fuel pressure, but provide no details. To some people testing fuel pressure means just putting the gauge on and energizing the fuel pump - a basic KOEO static test. But fuel pump problems are not always that simple. It might not be able to keep up under load. Its check valve may be preventing it from holding pressure. It might be so weak that it has trouble building pressure. Any of these can be affected by temperatures. I’m not saying that I think it is fuel. I’m just saying it’s got to be thoroughly investigated, and I don’t know anything about your shop so I don’t know what they do. I do know a lot of people are not very thorough and tend to be lazy.