Hey guys, this problem has really been getting to me now I can't figure it out my truck is running rich very rich the plugs have a coating of carbon on them thick coating I can clean the edge of my rolled tips and drive it 50 some miles there black again.
Its a 92 F150 5.0 4x4 5speed, I put a new fuel pressure regulator on it, I have a set of hedman long tube headers on it with no cats. The only check engine code it throws is thermactor air always up stream-45. The truck some times runs decent, but sometimes it just runs like crap. I am in a loss after my new exhaust was done I was getting 16-17mpg now i'm down to 12 and the performance just isn't there like it use to be. Low compression for performance it isn't 185psi on all 8 and at idle its making 19psi of vacuum. Anybody have any ideas?

Thanks
Curtis

 

does it come up to operating temp? if not the computer could be detecting a cold start and richen up the mix to try to warm it up. im pretty sure thats what mine is doing, but i think the po took the thermostat out for the summer so i think thats the problem on mine.

 

Its coming out of the cold start cycle, I always start it and let it go through the cycle at 1500rpms then it drops down to idle, its reaching up to the N on normal for its highest temp now, had to replace the water pump last weekend high flow pump 180stat.

Thanks
Curtis

 

I'm assuming that you have O2 sensor still? even with the headers? Without it you will be in closed loop. did you do any other changes at the time that you noticed the drop in mileage/running rich? BTW, there is a temp sensor for your temp guage and another one for your computer.

 

Yes I have the o2 still its right in the collector for the header. I noticed it about 2 weeks or so after the headers and new exhaust were put on but now its getting worse like cold start up it will run at 1100rpms and run like it has a cam. Here latley with the cold it has been kind of worse on gas. I mean I'm getting 12mpg same as my friends 92 bronco with 6"s of lift and 35s with a 302 it dosent add up right.

Thanks
Curtis

 

Check your fuel pressure regualtor, same thing happened to me. The truck ran very rich, loped like it was running a high lift cam, and when at speed ran well sometimes. The fuel pressure reading on the fuel manifold was 108 psig per the mechanic, about two times too high. Just take the vacuum hose off the regualtro and see if fuel is evident.

 

Hello,
Dropping to idle does not indicate that your computer has switched to open loop and taken control. The OEM thermostat is 192 so you are at least 12 degrees too low and combine that with a high flowing pump it might just keep you in closed loop for the duration of the winter/ cooler weather. Try changing to a 192 t-stat.
Let us know if that helps,
Popa Tim

 

Well the fuel pressure regulator is brand new ford oem regulator, this whole thing was happening way before my water pump crapped out, it had a 195 thermostat in it and was still running like this, its like my check engine light it comes and goes with driving put the scanner on it and it comes with code 45 thermactor air always up stream and that is something that dosent set the light off.

Curtis

 

What kind of code scanner are you using?
It seems very strange that you are not getting a code for something that would set a CEL.
Also you could run the KOEO and KOER tests found on fordfuelinjection. They will hopefull reveal something.
Cheers,
Popa Tim

 

Im using the snap on scanner my friend lets me use it when ever I need to used it many times I can go through and clear the code and it will come right back code 45. But still that shoulden't make the truck run stupid rich. Im thinking my exhaust is the culprit the exhaust is flowing way to much for the speed density set up I have heard many times long tubes will do that. But havent heard that it will run this rich. Looking like its time to convert mine to mass air.

Thanks
Curtis

 

Hey guys, well I got a new o2 for it extended the wires due to my long tube headers. code 45 is gone after I moved my air tube that goes into the exhaust past the o2 now i get a code 42 always rich. Its getting bad my mileage is dropping horribly, runs terrible sometimes half throttle it seems like I have 4 dead cylinders, oil is getting black at 675miles on this change. Is my 5.0 on its way out to the dead land? I'm out of ideas checking my o2 all I get is the volt meter burying the needle one one wire and nothing else on the other 3 wires.

Thanks
Curtis

 

Hmmm....maybe some leaking injector(s)? You can get a fuel pressure gauge and see what it is. At idle, it should be ~35PSI with a very slow bleed-down.

 

ok, you said you were getting thermator always upstream and now always rich. if the air pump is always dumping air upstream (manifold) you will have too much air there. the oxygen sensor comes after that point and will sense too much air increasing the gas flow which is why you get a rich reading. you need to fix whatever is wrong with your thermactor system.....TAB, TAD solenoid, TAB, TAD valves or any vacuum lines to them

 

FPR is 3 months old from napa checked it last month was at 35. the Upstream code was due to my AIR tube dumping air into the exhaust before the o2 causing it to run rich now with it moved to past the o2 it gives the code 42. but runs decent sometimes like complete crap other no matter what the gas mileage is like a 460 with a 1.9 powering it when its at its worst point.

Thanks
Curtis

 

do you have your EGR hooked up?