1990 Ford F-150 Cold start stall

bobjd445

1990 f150 4.9 52,000 miles. First start in the morning starts hard then dies. Second start, and truck runs fine all day. Changed IAC, TPS, PCV valve, cleaned IAT sensor, throttle body mounting gasket, and checked for vacuum leaks. Still dies on cold start.

bobjd445

bobjd445 said:

1990 f150 4.9 52,000 miles. First start in the morning starts hard then dies. Second start, and truck runs fine all day. Changed IAC, TPS, PCV valve, cleaned IAT sensor, throttle body mounting gasket, and checked for vacuum leaks. Still dies on cold start.

bobjd445

Also cleaned throttle body and as much of intake as toothbrush would reach. Does not throw any codes

bobjd445

bobjd445 said:

bobjd445 said:

1990 f150 4.9 52,000 miles. First start in the morning starts hard then dies. Second start, and truck runs fine all day. Changed IAC, TPS, PCV valve, cleaned IAT sensor, throttle body mounting gasket, and checked for vacuum leaks. Still dies on cold start.

bobjd445

It,s my daughters truck, and I want to fix it. Any one had the same problem and found the fix?

thecardoc3

Are the fuel trims making a large correction at idle when warm in closed loop?

bobjd445

thecardoc3 said:

Are the fuel trims making a large correction at idle when warm in closed loop?

bobjd445

I don't have equipment to test that

Mr_Shiftright

Running too rich – High negative fuel trim corrections can be caused by MAF sensor problems, high fuel pressure, leaking fuel pressure regulator diaphragm, faulty evaporative emissions components, leaking injectors, defective O2 sensors, exhaust leaks before the O2 sensor, coolant temp sensor problems, and base engine issues such as low compression and incorrect camshaft timing.

Running too lean – High positive fuel trim corrections can be traced to MAF and O2 sensor faults, vacuum leaks from intake gaskets/hoses, unmetered air (intake snorkel leak), clogged or dirty fuel injectors, fuel delivery issues, and exhaust restrictions like a clogged catalytic converter.