Chrysler Repair: Chrysler 3.3 liter engine quits in hot weather, plymouth grand voyager, fuel pressure regulator

Question
QUESTION: Hi:

Own a 1990 Plymouth Grand Voyager with the 3.3 liter engine. For
several years, I have experienced a nuisance problem that appears to be temperature related.  I live in Colorado at 7200 feet.  

In the summer months late in the afternoon I will experience a condition where the car quits.  It almost seems as though it is vacuum locked but since this a multi-point EFI system, you would not think the car can vacuum lock.  When in this condition, I don't belive it is getting fuel.    

The first time it happened, I was convinced it was the fuel pump.  In the end I think I replaced a perfectly good pump.   

The only way the condition will clear itself to wait a few hours until things cool down and the car will start right up.  

Car shows a code 34 - speed control circuit issue.  

Any experience with this kind of problem.  Fuel pressure regulator?

Randy


ANSWER: Hi Randy,
You may have a sensor that is inaccurate but not so badly as to set a code. The coolant temp sensor should read across its terminals 700-1000 ohms (2-wire plug disconnected) when the engine is at operating temperature, so check that out. It is located near the thermostat housing and the coil pack plug. If it reads much more than 1,000 with the engine hot, that would cause a too rich mixture.
Another item that can lean out the engine is the egr valve should it begin to get stuck ajar rather than closing when you are at idle. It is located very close to the throttle body in a horizontal conficuration (the valve stem is horizontal, located between the vacuum actuator on the top and the body of the valve that is mounted in the small branch-off exhaust pipe from the rear exhaust manifold. The valve stem is hidden behind a flange between the actuator and the vody of the valve.) Put the tip of a screwdriver in the slot of the valve stem so as to be able to move it back and forth, against spring-action trying to close it. Make sure it mover freely and the spring closes it to a dead stop. If not, spray some WD-40 on the stem where it enters the body, and work it back and forth.
The MAP sensor too could be inaccurate but no so badly as to set a code, but I don't see that as being temperature dependent.
Because of the 34 code it would be good too to check the vacuum lines that connect to that system's vacuum reservoir and the intake manifold and from there to the control module for the cruise control. If a hose was detached or leaking due to a crack that would explain the 34 and also cause a too lean mixture.
So there are 3 possibilities to look into that are mixture-related. Also, you might verify when it shuts down that you have spark as another possibility is that the cam or crank sensor can fail when it heats up, only to recover with cooldown. It should cause a 54 or an 11 code, however, were that the case.
Roland

---------- FOLLOW-UP ----------

QUESTION: Hi Roland.

Thanks for the detailed response.

I think the code 34, which could be vacuum related is a good line of inquiry for me to follow.

I forgot to mention that I have also seen a code 17 - Engine runs cold too long.  You brought up the coolant temp sensor....

I am wondering what the failure mode of that sensor is.

You brought up the notion of the sensor causing the car to run too rich: "If it reads much more than 1,000 with the engine hot, that would cause a too rich mixture."

In my case, I keep thinking something is starving the fuel supply or causing a very lean mixture.  Can that temp sesnor fail in a manner to cause the mixture to be too lean?  Could that code 17 also point to the coolant temp sensor?   If the computer thinks the temp is really cold, would it cause the mixture to lean out?

Thanks

Randy

Answer
Hi Randy,
The failure of the sensor (voltage too low or too high) is 22, but 17 may mean failing, or thermostat stuck open.
If pcm thinks the engine is colder than it really is, it will enrich the mixture more than it should be.
I am unaware of whether if it reads 500 ohms it will make it too lean, but why not measure it when the engine is hot and find out.
I believe that too rich/too lean if not extreme could be similar symptomatically in terms of poor/no start, no idle.
17 certainly could point to the sensor. When cold it should be 7,000-13,000 ohms.
But also, I believe that just because it is multi-point injection doesn't mean that it can't vapor lock, so you might try cooling down the incoming fuel line when this happens and see.

Roland