I have an 87 f150 with efi 5.0, it recently started running rich, so I pulled the codes, that didn't help. Replaced the EGR valve and sensor, O2 sensor, IAC, Plugs, PCV valve, valve on brake booster, Rotor and cap, fairly new plug wires, and I cleaned the throttle body. I also checked for vacuum leaks, by spraying windex on all the vacuum lines. it still runs up and down at idle, from 300-1200 rpms, and it is running rich, I usually get 10-12 miles per gallon, now I'm getting 5. I also shoot dark smoke out when I rev it up. can anyone help.

 

Check the fuel pressure regulator, the diaphram may have ruptured, causing fuel to be sucked into the intake manifold. Pull the vacuum line off of it and see if there's gas in it. If that happened, change the regulator and change your oil, it'll have gas in it.

 

hey thanks I'll check it and tell you what happens. hopefully your right.

 

no luck, I use a vacuum pump and suck on the regulator, but didn't get any liquid gas. I dont know what else to check. but hey thanks anyway

 

Sounds like it could have a bad head gasket. If the problem keeps up, your engine may blow so you might want to get it taken care of pretty quick

 

reconrider40.......sounds like the same thing i went through...put a fuel pressure gage on the fuel rail (looks like a tire valve) and check perssure..check at idle then rev it and take a reading...mine would show normal pressure at idle but shoot up over 100 lbs when i reved it...pressure regulator goes on these fords....one more thing, if it is the regulator and u keep driveing arround like that u stand a chance of blowing out one or more injectors from over pressure...hope this helps...91 f150 5.0..

 

to fix the black smoke problem, a quick fix would be not to rev up the engine... heh heh... sorry, had to say it. this problem's outa my league. keep up the good work boys.

 

check to see if you have vacume at the egr the way the lines are run they are easy to melt. my tuck has a 351w and it is in cherry condition it is a 90 f150 and the reason he sold it was because nobody could figure out why it was running rich and I found all the vack lines were melted together and my fuel pres reg was bypassing on a load now the truck runs like a new one now...

 

hey did u guys ever find out the problem?? i got the exact problem and its gettin worse

 

I have the same problem too - have you tried what was suggested? Have you found anything that has worked?

 

hey thanks, I just bought a new map sensor, but no good. I ll try the pressure regulator and get back to you.

 

I haven't had a chance to check fuel pressure, but I had a question. One of my friends dads owns a shop, and he said to check my ECT sensor, and my dfpe sensor. what are the symptoms of a bad ect sensor, and the DFPE. I check the vacuum on the DFPE, but it didn't hold out of either inlet. I think it is a one way valve and it is leaking. if anyone can give me any info it would help.

 

Just as a heads up - I pulled the codes from my EEC last night and found a code 22 - MAP sensor out of range. I tried doing some tests on it with a volt meter but it wasn't working to well - does anyone know if the 87 f150 302 MAP sensor uses a voltage signal or a frequency signal?
Anyway I went out and bought a new MAP sensor and installed it, and so far it has completly solved the problem. At first it didn't seem to work but then I reset the computer by pulling the battery for 10 min (after the truck was warm) then let it sit and idle for 2 min in park, N, R and drive. Now when I come to a stop light I can't even tell if the engine is running it's so smooth. I'm going to pull the codes again tonight and see if the code 22 has gone away - I figure if the truck continues to run well for 2 days the problem is solved!
Sorry but I can't help out on your last post - I don't know what those things are!

HAZA!

 

I ran a code check on mine and got a 34 and 42, o2 reads rich, and too much voltage on my evapo system. I am not sure what that means. it said high voltage at closed limit. I found too more vacuum leaks today, and replaced the hoses, and it is running a little better, but still rich and every once in a while it runs up and down at idle.

 

can anyone help with Evap diagnosis, that is the code I got and I am not sure what to do. I ve never heard of it before. thanks