I've got a 92 f150 with the 4.9 I6, About 2 days ago my truck began to have a lot of hesitation when you hit the gas. The engine would bog down and you wouldnt go anywhere. Today the problem is much worse and I also had difficulty getting it started when the engine was cold this morning. When I got up to about 65-70 on the highway and maintained a steady speed I didnt have any trouble at all, It was only during acceleration. At first I thought it was some bad gas but I switched over the the second tank which was filled at a different station and same problem. I changed the filter just a couple months ago. What I don't get is that these trucks do have a pump for each tank right? If that is the case I wouldnt think they would both go bad at the same times.

What else could be causing this?

Any help is greatly appreciated



any advice is appreciated

 

You said hesitation and not a steady miss. I would expect it to be fuel related. Ignition problems normally result in a miss. Hard starting cold also points to fuel starvation. You should have pumps in both tanks and another pump used to pressurize the fuel rail. The pumps in the tanks are to keep the pressure pump fed with enough volume. I would suspect that the pressure pump is going bad and that as long as you don't have a big demand for fuel ( crusing or warm starts) that the in tank pump are picking up the slack.
Just a thought

 

I agree it's most likely fuel related. Check fuel pressure at the fuel rail it should read 50-60 psi for the I-6. if the fuel pressure tests OK, then you should have the Map sensor tested, since your '92 uses speed density to contoll the fuel injection. Ford Map sensors are frequency type sensors you'll need a Map sensor tester to check it. It should read about 156 HZ at sea level. Anything less than that will cause starting problems & hesitation. BTW, the '92 F150 does not use a high pressure fuel pump on the frame. Ford done away with those after the '89 model year. hope this helps.

 

thanks for the help guys, that helps a lot. I'll go ahead and check the fuel pressure and then the Map sensor.

 

Also Check the air side of the equation. Is you air filter clean? Do you think that your cats are clogged? Check your Vaccuum readings and compare to normal from a Chiltons.
Jes

 

ttt

 

I still havent figured this out yet. my computer isnt returning any codes. I have replaced the fuel filter, air filter, and the MAP sensor and I'm still having the same problems. hard start when cold, hesitation while accelerating. i've also been told the O2 sensor could cause this You guys think this could be?? It sucks when you dont even know what the problem is.

Any suggestions you guys have are appreciated

 

I'm thinking your fuel filter might be clogged again.Change that out,see what happens.If that dont do it look into the fuel pressure regulator.

 

I just replaced the fuel filter again today and the fuel pressure checks out where its supposed to be. The computer is now giving me a code for a bad EGR, would that cause the symptoms that i described?? Couldn't I remove the EGR all together and put a block off plate there? Have any of you done this before and if so what problems did it cause? I really dont care about emissions i just need to make this run right and avoid future problems with a part that really isnt necessary.

 

The EGR valve might cause hesitation problems, but I've never seen one cause a starting problem. You can disconnect the vaccumn line from it & plug it off to see if the hesitation problems go away. Do you notice any black smoke from the exhaust when the starting & hesitation occurs? If so,I had a '93 F150 do this once, the problem was raw fuel was getting drawn into the throttle body through the fuel tank vapor purge hoses from the fuel tanks. Ford had a TSB on this. Try disconnecting the fuel vapor hoses from the thottle(there is 2 of them) & plugging them off & see if the problem goes away.

 

ttt

 

Well it looks like im going to be heading to the mechanic in the morning So far Iv replaced the egr, O2 sensor, fuel filter, air filter, and iv cut out the cat. i've also check the fuel pressure and it looked good. Still have the same problem hard starting and bad hesitation while accelerating. Its frustrating as hell when you cant even find what the problem is. I was thinking for a while it may be a bad coil but im tired of spending money on **** that doesnt fix it.

 

Not sure if you have a throttle positiion sensor but if you do that may be the problem it is located on the throttle body I had that exact same problem on my 88 F150 howeveer i had the 5.8 so I am not sure about the I6.

Richard D.

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