My 1996 Grand Caravan (3.8L V6) does not like hot (> 85F) weather. The failure does not occur at the initial start when the engine is cold. In that case it starts and runs fine. The failure does not occur in cooler weather either.
The problem is that, in warm weather, it does not start up and run well when I RESTART it after it has throughly warmed up. In this case it will start and try to run, but very roughly. It will barely keep running, idles slowly and roughly and often dies. I can sometimes qoose the accelerator for a few seconds and get it to “clear its throat”; then it runs fine. Other times, It dies when I goose it and eventually won’t start at all. I don’t smell anything unusual under the hood. Cranking with the accelator on the floor does nothing. It cranks fine, no issues with the starting circuit. It does heal itself if I let it sit for a while (an hour) and then runs fine.
I have had this problem before but I cannot clearly remember the fix. It may have been new plug wires although that makes no sense to me.
Any Ideas? Fuel system? Vapor lock?
Thanks,
Jerome
In order to cma, I will say I am NOT a tech.
You MAY have answered your own question concerning a possible fuel vapor lock.
It has been noted in other previous posts here that when the ambient temp climbs into the 90s and upwards, the fuel tends to “boil”. This can contribute to (or cause) vapor locks.
It also may be possible the fuel pump can’t handle the excessive heat either. (?)
You said the engine turns over fine so that eliminates the suggestion of a possible heat soaked starter or a weak battery.
Without carrying tools around all the time in order to check things like a possible lack of fuel when the engine dies (stutters to a stop), spray a little bit of starting fluid into the air intake and crank the engine over.
If it starts then dies, a lack of fuel is the problem. (Whether due to a vapor lock or something else)
One way to test for fuel pressure to the injectors when hot (or any other time) is to remove the cap from the Schrader valve, cover with a rag (to prevent fuel from spraying all over you and the engine) and depress the valve.
This valve is incorporated into the fuel rail and looks exactly like a bicycle tube air valve. There may or may not be a shroud covering this (upper) area of the engine.
If there is lots of fuel, you’ll next need to check for spark.
Vapor lock is unlikely. A failing camshaft position sensor or MAP sensor can cause this problem. You need to determine if the engine lacks fuel, spark, or both when this happens.
Holding the gas pedal to the floor does the opposite of what you might think. It CUTS the fuel injection signal from the engine computer. It’s a technique to un-flood an engine.
Cars used to vapor lock on the “draw” side of the engine mounted fuel pump. Then, the fuel pump couldn’t “draw” the fuel and push it to the engine. Today’s fuel pumps push only, from the fuel tank. Pressurized fuel won’t vaporize except in very extreme conditions.
You need to do some sleuthing. You need a couple of simple tools: a spray can of Starting Fluid (or, similar name), and a spark tester. Some auto parts stores (and ebay) have a pencil size inductive light that you lay along the spark plug wire while the engine is being cranked. If the light doesn’t flash, the spark plugs aren’t, either. Practice with this light on a cool engine.
If there seems to be adequate spark, use the Starting Fluid in the engine air intake tube. If it starts, and runs for a few seconds, there is a fuel problem. “Fuel problem” includes the action (or, inaction) of the fuel injectors.
There’s more stuff, but, this will be a start. You can get the troubleshooting charts from www.alldata.com. If your public library has a subscription to alldata, this would be free to you. Call and ask.