Crazy trouble REstarting a warm car so I did


#1

All the other cars I had before started better after being warmed up. My 2005 Impala starts perfect when cold first thing in morning but if I go somewhere quick and try to start-up the engine warm it fights it’s self and car shakes and it’s super rough start . So I figured it’s the hot vapors in the engine so I Remove the oil cap and it starts better . I am no mechanic or know about engines . Please feel free to comment on my theory and post better thing to do to start a warm engine .


#2

I can’t imagine what removing the oil cap would do. I’m sure this is a coincidence and has no bearing on whether your car starts or not. When was the last time you had a tune up? Is your check engine light on? I’m thinking it probably is. Have you had the codes read?


#3

+1 to oblivion’s comments and questions.
However, I want to add another thought:
If there really are “hot vapors” that are trapped in your engine, that is extremely good evidence that the PCV valve/hose is gunked up, and that is not a good thing–for many reasons.

However, like oblivion, I believe that the OP’s theory is bogus, and that the hot start problems are more likely to be the result of either lax maintenance (that would include the PCV valve, of course) or leaking fuel injectors that are essentially flooding the hot engine.


#4

I like the leaking injector theory.


#5

Is your check engine light on?

There are several things that can be going on. There is a build up of heat under the hood when the engine and all of that gets hot. The oil cap is probably a red herring and “real” cause of easier starting (if that’s real and not just an impression) is probably just opening the hood - and whoosh - a whole bunch of that under hood heat takes off for the stratosphere.

A lot of ignition problems first show themselves because of heat so you’d worry about the ignition coils and wires.

If your fuel pump doesn’t hold pressure well the heat under the hood can vaporize the fuel in the fuel rail, especially with winter blend fuels. You could try cycling your key to run-off-run-off-run-off etc. (run is where the dash light all come on but before it cranks) whenever this is likely to happen and see if it helps. This repressurizes the fuel rail. Hitting the gas pedal after it fires a bit should also help clear it.

The hot injectors can also be getting leaky and flooding the engine (as noted). Holding the pedal to the floor while cranking is a flood clearing procedure.

EGR valves can stick open and act like a big fat vacuum leak.

There’s probably other stuff… I’d want to know what the fuel pressure does when the car is shut down hot, and what happens if you prime up the fuel pressure before restarting.


#6

I’d get a fuel pressure guage on it. If the pressure drops after shutting it down after a short run, the injectors are leaking or that ball valve in the pump. If the pressure is good, I’d be looking at a faulty engine temp sensor or air sensor. I had a Dodge Dart like that and was a choke issue which is essentially a fuel/air mixture issue at that in between temp. A diagnostic computer though would be able to see the readings from the sensors and see what it should be. They can also do the fuel pressure test. So you take it in the night before so they can replicate the conditions.


#7

hot injector leaking looks like the clear winner . I want to add I have no check engine lights and my sparkplugs and the wires are super premium and about 6months old and I have used the clean egine gunk before i changed the motor oil .


#8

@timekillweekly

“no check engine lights” doesn’t mean much, unfortunately

All it means is you don’t have any fault codes which are commanding the light on

You might have fault codes which don’t require the light to illuminate

Something to think about . . .


#9

If your car is shaking like crazy at startup, that’s a misfire, which would normally make the check engine light start flashing. Even if the CEL isn’t currently on, it would be worth having the codes read to see if there are any ‘pending’ codes, which would make troubleshooting the problem easier.


#10

Problems w/hot starts are not infrequent here, and in quite a few cases it has been the crank or cam sensor on the fritz.