i have a 1990 f150 with the 4.9l straight six. my engine is sputtering and sometimes when i stop it will stall out and die. there are times it will run fine and times it runs like sh**. im just trying to see if it worth fixing it and what is wrong with it. PLEASE HELP. But there is a vacuum line i unpluged that goes to the fuel pressure regulater and the truck will run ok. but when i plug it back in it runs at a real low rpm and dies.

 

Fuel filter?

 

i replaced the fuel filter and now it stays running but it still sputters when i accelurate

 

My guess either a bad pressure regulator or the fuel pump is starting to go. Had a simliar problem with my truck, replaced fule pump, problem solved in my case.

 

not to steal your thread but i have a similar problem that maybe someone has an idea on... 91 f150 4.9L 18 gal. tank... couple weeks ago the truck began to start rough (usually the first time) (cold or hot) and run rough and stall, then when starting the second time would run just fine and usually drive and accelerate normal. Then it started having trouble clearing out and would run rough for a mile or so. Unfortunately I was unaware of the fuel level guage discrepancy and ran it out of fuel. Now it runs like crap all the time (chugs, spits and sputters) while still starting the same (off and on). Thought it was the filter too and changed it (had no flow problem when I poured it out in either direction). Could it be a sensor or do ya'll think it is just the pump goin out. I have not seen a pump last this long when it was goin out so I am a little confused on that solution.

 

im having the same problem in my 88 4.9 and im just as clueless codes came out clear can hear the fuel pump engaging and sparks good and new tps sensor and still doing it???????????? so glad im not the only one with this problem

 

Check running fuel pressure, probable pump and pick up mess in the tank. In tank level gauge also part of the equation as being malf.

 

another thread hijack, sorry I have an 87 4x4 4speed 300 with good spark, and no injector pulse, fuel pumps will not turn on from the computer, it sends no ground signal to trigger the F/P relay, this is a problem that is driving me crazy! I have replaced a computer that had visable water damage and a horrid smell! checked al the grounds and all are good clean and tight! can someone here possibly help me in this major problem! the truck ran before with the F/P diagnostic plug jumped to ground, and it ran good, then a week later the truck just died! fuel pumps running, and no pulse good spark though! Blue-purple spark

 

Hey LeRoy, yeah, you are a high jacker, but not the all time winner. With you having spark but no fuel as I understand you, look toward the Crankshaft Position Sensor. I think back in those days, it signalled the computor when to fire off the injectors.

Old shool troubleshooting, will the engine start with fluid sprayed into the intake? If so, then concentrate on the injectors or what controls them as being the issue.

 

Leroy you should have 12 volts at the fuel injectors with the key in the run position, if you don't check your relay.

4x4 check your fuel psi.

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