1987 F150 rough idle, stalls, smells rich

There are several possibilities for this problem. A "cold start" sequence is suppose to activate based on water temperature and the signal from the water temperature sensor. This makes the fuel rich and adjusts timing to make the engine run better when cold. It works like a choke only it is electronic.

There may be 2 sensors with one making the dash gauges work and the other doing the engine controls. If not 2, then 1 sensor would do the whole job.

Another possibility is an air leak in the fuel system which makes the system bleed dry overnight. It is far less common on gas engines but happens a lot on diesels.

Some earlier Ford engines from 1984 to I don't know when they stopped on trucks, would use a step-up solenoid on the accelerator bracket that worked off water temperature. Sometimes a bad water thermostat would make the temperature controls malfunction the other way (High idle, clicking, low idle) that would stall and engine as the temperature vary.

This is a lean Code. What is happening is too much air is entering the engine and the O2 sensor is making the engine run rich to rebalance the fuel ratio.

You need to find the leak. Use a spray bottle of water while the engine is running. When you spray over the leak, the rpm will change or the engine may even stall. This is where repair is needed.

air sensor or fuel sensor it is mixing to rich

Maybe sensor is not for a bigger engine

If exhaust is rich, you may have excessive fuel getting dumped into cylinder(s). A sicking or leaking fuel injector can cause this. How many miles are on the engine? Improperly seating valves can cause this also. Or if timing is incorrect.

try replacing the throttle position sensor

What engine?

sounds like you are not geting the right amount of air to fuel system.Have you checked the air filter is clean.Change the air flow senser if it is clean.Good luck!!

1. change air filter. 2 check timing. 3 check all fuel lines and connections for leakage. 4. dirty or clogged injectors.

Check and clean the IAC valve. Idle Control Valve. Use brake cleaner or carburater cleaner . Remove the duct work from the air filter assembly. It is located just inside . Run the engine at 1200 rpms and spray the valve. The valve can also be removed and cleaned.