Hello all my nephew bought a 89 f150 with a 300 straight 6 motor a few months back. It had been sitting for couple years not started but motor and everything is in good repair. When he put gas in he flush the tank a couple times to clean out any old debris and such by changing fuel filters several times. He finally started it to run which it idles just fine, however he puts in gear and it dies. Any suggestions for what yo maybe check out? He feels like it’s something simple but not sure what. Any tips or advice appreciated thanks

 

Since it has sat for so long, I would suspect a fuel issue. Start by checking fuel pressure off the sharader valve on the fuel rail. The spec. for the 4.9 is 45-60 psi at idle.With the long inactive period, I would also check vacuum lines and replace the plugs if those haven't been done already. I would also pull the IAC solenoid to clean the throttle body bore and the pintle.

 

They did have problems with the original coils on those approx years.
The coils would break down internally under load.
Replacing with a new coil took care of the problem..

 

Thanks to both I will let him know, he was thinking maybe throttle position sensor. But unsure that make it act like that. Is there any kinda of way to access codes that it might have. I know it would be an obd1 but is there any other way to manually access codes on that particular motor where it might give hint to what’s maybe going on?

 

You might try ,
Tool Source--- 1-800-2202-8350

Ford ABS/EEC IV trouble code tool $20.75.

Used one of those for several years. Worked great, also performed Dynamic testing. The ECA in those years had internal programming that conducted running tests and provided codes for any faulty operations.

Those were the days when a tech had to rely on knowledge to conduct certain tests. Today you just plug in a tool and easily get any codes.

If you can obtain one , be glad to offer any assistance , they did come with directions.

 

Or you can just use a jumper wire in the diagnostic connector to read the codes.If you search "using paper clip to read Ford OBD 1" the procedure is described.
The probem is, the items mention above likely won't set a code which is probably a good thing. These systems were so vague, many change all kinds of items while chasing a particular code which was set, only to find the problem still remaining. Troubleshoot, test before replacing anything.