1986 ranger smokes and stalls

Cougarman · Nov 9, 2013

I have an 86 ranger that seems to smoke a bit and stalls quite often. I checked for codes and got code 21 and 95 for koeo. And codes 21 and 42 for koer. The truck starts right up but will only run for a few minutes and then it will stall. So the truck really never gets to a normal operating temp which is why I assume the code 21 comes up. I checked the fuel pressure and I get 20psi with key on, between 32-33 with engine running, 42 with vacuum line off and 40 when you give it gas. Anyone know if these are normal not sure where to get the specs from. Also when the vehicle is shut off it holds pressure. Any ideas would be great thanks.

RonD · Nov 9, 2013

Fuel pressure numbers are good.
30-40psi is expected.

Although 20psi with key on is low, but you should have also seen a pressure drop with key off after the running test, so not sure where the first 20psi would have come from???

Did you check the Fuel Pressure Regulator's(FPR) vacuum line, I know you removed it for the pressure test, but did you check it for fuel.
A leak in the FPR diaphragm will cause raw fuel to be sucked into the intake, flooding out the engine.

An injector may be stuck open.
You can often use a small hose to listen to each injector while engine is idling, you should get a steady "click, click, click" from each injector, if one sounds "funny" or doesn't "click" then it is stuck.

The ECT(engine coolant temp) sensor is the "choke" for a fuel injected engine, it is a 2 wire sensor used only by the computer.
There is a 1 wire Sender that looks similar but is for the dash board temp gauge.

The ECT tells the computer the engine temp, if cold the computer runs engine rich, raises idle and advances timing(choke mode), as ECT sensor warms up computer leans out the fuel mix, lowers idle and sets regular spark timing.
The computer has a timer that activates when engine is started, if ECT temp is not changing or not changing fast enough you will get code 21, timer is usually set for about 5 minutes, if you get the CEL before that ECT or the wires could be bad.
They are easy to test with OHM meter.
Good site here for Ford sensors:
http://oldfuelinjection.com/?p=28

Cougarman · Nov 9, 2013

Thanks for the response. When I first hooked up the fuel pressure tester and turned the key on it went to 20psi. The vacuum line to the fuel pressure regulator was dry. I will have to take a look into the injectors tomorrow.

RonD · Nov 9, 2013

The '86 should still be using a MAP sensor, this tells the computer what "load" is on the engine via Vacuum pressure in the intake, so this is part of setting the fuel/air mix.
The MAP sensor is usually located on the firewall toward passenger side of center.
It has a vacuum line and electrical connector.
Follow the vacuum line to find it, often hidden behind the wire harness.

Check to make sure it's vacuum line is not cracked or broken, and electrical connector is clean and dry
You can test it with a Meter that has a Hz setting, this sensor outputs a frequency not a voltage.
Some auto parts stores can check them.
MAP sensors rarely fail, but not never fail, so it is reasonable to test this sensor when fuel mix is an issue.

Cougarman · Nov 14, 2013

I found I may have a short in one of the coolant sensor wires. However when I traced the wires I found where they plug into the harness in the back of the engine bay on the drivers side the wires go into a connected and on the other side of the connector there isnt another wire coming from the same pins. Are they all like this?

1986 ranger smokes and stalls

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