Warm weather issues

[bruisedreed]

I have a bit of a puzzle with my Ranger (1993 4x4 3.0L). It only crops up when the weather gets hot (like over 80 degrees). It will run as smooth as silk UNTIL I shut the engine down. After that it when you start it up it develops a pretty bad miss and runs rough. The miss does not seem to be consistent to one particular cylinder when I have pulled codes. If you let the engine cool completely, it will run perfect again and once it's running you can run it all day long like that without a single hiccup. Once it is shut down the same thing will happen. In cooler weather it never happens. As far as engine temp it does not seem to be out of the ordinary. Thermostat opens and closes, coolant flows and maintains a normal operating temp.

I have done the basic, cleaned MAF sensor, IAC, plugs and wires, checked for vacuum leaks and nothing seemed to make any difference. I wondered head/head gasket issues, but when I checked there was no combustion gas in the coolant (and I'm not loosing coolant) and I haven't had any of the classic symptoms. I compression tested each cylinder and had nearly even 150psi on each cylinder so again I don't see any indicators of anything amiss in one particular cylinder. I have read a bunch of issues related to fuel pumps but I wouldn't think that would be a repeatable thing that doesn't seem to get worse and only happens in a certain setting. I am thinking the next step is to start checking fuel pressure and maybe injectors and other fuel system components but I was just curious if this is sounding familiar to anyone. Thanks in advance!

 

[superj]

if it was a vw, i would say vapor lock but thats not so much an issue since fuel injection came out with return lines to the tank

 

[RonD]

When you shut down a warmed up engine the cooling fan stops, so no air circulation, and engine bay starts to heat up, and if its also warm outside then it will get pretty hot under the hood
So what you are describing is a "heat soak" issue

Try this test
After you get home and engine is all warmed up, shut off engine
Open the hood
Let it sit for...........??? and then try a restart and see if there is less of an issue or no issue at all

This would confirm heat soak is the issue

Possible culprits in 1993 3.0l
The ignition coil itself, these can get heat sensitive

The 1993 3.0l has a remote mounted TFI module(spark module), its on the rad support, engine bay side, usually on drivers side under the battery
TFI modules were known to get heat sensitive which is why the 3.0l had a remote mounted one, these used to be on the distributor(2.9l) and heat soak was a common issue

You could cool either of these with a bag of ice held against them to see if the extra cooling allowed for a better restart, if so replace that unit

Vapor lock wouldn't be common issue on fuel injection engines since it runs 30psi fuel pressure, and fuel under pressure won't boil/vaporize
BUT...........if you are losing pressure with key off so it drops to 0psi then the fuel in the engines fuel rail could vaporize, cause your symptom
So you may want to test fuel pressure, there is a test port on the engine, and see if its dropping to 0psi with key off, it should hold above 15psi for MONTHS and MONTHS
The test port is a shrader valve, exact same type of valve thats on a tire
So you could test if there is fuel pressure in the system in the morning, COLD ENGINE, by press in on the center pin, should have a squirt of fuel out, which could be dangerous on a warm engine, lol

 

[bruisedreed]

When you shut down a warmed up engine the cooling fan stops, so no air circulation, and engine bay starts to heat up, and if its also warm outside then it will get pretty hot under the hood
So what you are describing is a "heat soak" issue

Try this test
After you get home and engine is all warmed up, shut off engine
Open the hood
Let it sit for...........??? and then try a restart and see if there is less of an issue or no issue at all

This would confirm heat soak is the issue

Possible culprits in 1993 3.0l
The ignition coil itself, these can get heat sensitive

The 1993 3.0l has a remote mounted TFI module(spark module), its on the rad support, engine bay side, usually on drivers side under the battery
TFI modules were known to get heat sensitive which is why the 3.0l had a remote mounted one, these used to be on the distributor(2.9l) and heat soak was a common issue

You could cool either of these with a bag of ice held against them to see if the extra cooling allowed for a better restart, if so replace that unit

Vapor lock wouldn't be common issue on fuel injection engines since it runs 30psi fuel pressure, and fuel under pressure won't boil/vaporize
BUT...........if you are losing pressure with key off so it drops to 0psi then the fuel in the engines fuel rail could vaporize, cause your symptom
So you may want to test fuel pressure, there is a test port on the engine, and see if its dropping to 0psi with key off, it should hold above 15psi for MONTHS and MONTHS
The test port is a shrader valve, exact same type of valve thats on a tire
So you could test if there is fuel pressure in the system in the morning, COLD ENGINE, by press in on the center pin, should have a squirt of fuel out, which could be dangerous on a warm engine, lol

Thanks for the great info. All good suggestions.The interesting thing is that the missing starts The second it is shut down and restarted. It isn't like it sits and heats up a bunch. I will chase some of the fuel/fuel pressure stuff around and see if I learn anything

 

[RonD]

If its instant then the coil or TFI module would be my first guess

 

[bruisedreed]

If its instant then the coil or TFI module would be my first guess

Dead on...I did the TFI module and so far so good. Hot week coming this week so we'll see. I appreciate the input and help on this one!