I have a 1990 f150 with the 5.0 142,000 miles. The truck was running great, stopped at a stop sign went to accel through the intersection and the truck began to chug and pop as if running out of gas. I let go of the throttle ans it'd even out idle smooth. Go to accelerate and it begins too miss spit and sputter. Ran codes and got EGR and map sensor changed both with no change in running. When cold it can't idle on its own it wants to stall out. Strange knocks coming from the engine block occasionally. I know the truck is old but it's all I got. Any help, any direction I should go?? Thanks in advance.

 

Chris -- no reason to be close to stumped as there are tons of videos, info on the internet to help diagnose -- plenty right here on this site too. I don't like swapping parts into any vehicle as many come bad OUT OF THE BOX. Rather, I try to isolate to the specific problem (or problems) -- all vehicles have or develop problems (irrespective of brand) --- your truck (due to the fact it is the best selling vehicle out there) has one advantage over most, if not all others === reasonable parts costs given the sheer size of the market. Typically, F-150 parts are 1/3rd to 1/2 the cost of parts for other vehicles, especially imports where owners often get gouged on parts (I drive a 20-yr old 911 and get rip'd off badly when I purchase items for it)

I'd start with fuel pressure checks at idle, then increased RPM and if it turns out your in-tank pump is bad, I'd look for a Motorcraft (Ford), Bosch or Denso pump first and avoid the low cost pumps as they may last a year, but usually not much longer. Here's a great site with plenty of relevant info to help your diagnosis..........best to stick with basics and eliminate one source of the problem (e.g. distributor/ignition, sensor) at a time.............the section on "Troubleshooting EFI Problems" is very useful and the order to follow very logical:

Fuel Injection Technical Library

 

last time fuel filter changed, last time tune-up, if you cleared codes, when you fixed last issue, you could try running them again, see if new come up,

 

Thanks for your interest. I put a fuel gauge on it and got 29 psi with key on engine off. With engine running it stayed at 29 psi. While revving it dropped as low as 20 psi. It took me a few times turning the key to get it to 29 with engine off. Is that normal??

 

Fuel filter hasn't been changed but removed it and can blow through it. Tune up at 141,000 miles. With oil change new plugs and wires and air filter. Pcv valve was has also been changed within last year. Used my father's computer to clear the codes.

 

should be 31-32 idle, and when rev/blip throttle it should go up in pressure(35-40), with truck off, on the fuel pressure regulator if you remove the vacuum line, does the vacuum line have gas running out, or smell, gas in line? if it does could be bad regulator, before assuming fuel pump, do you have 2 tanks? check what pressure is on both if you do,