P0171/P0174 - Already replaced almost everything

[snoranger]

Any suggestions for dropping a full tank without killing myself

Yes.... Dont do it.


Fuel pump thread

 

[joe doe]

those codes are usually caused by an air leak somewhere .
when you done the upper and lower gaskets did you replace the plenum gaskets?
they would look something like this here

if not then you need to do so .
if you did replace these then your leak is elsewhere .since you have both codes i would suspect a large leak ,like an emissions hose on the upper intake somewhere .i have seen this on the v-8 before as well .
i am not familiar with the ohc engine much as i have the pushrod ohv engine but the codes mean the same thing and i been there done that .
replacing you fuel pump will not rid you of these codes . not that it isnt good maintenance but dont expect those codes to go away .

good luck.

 

[blue89bird]

those codes are usually caused by an air leak somewhere .
when you done the upper and lower gaskets did you replace the plenum gaskets?
they would look something like this here

if not then you need to do so .
if you did replace these then your leak is elsewhere .since you have both codes i would suspect a large leak ,like an emissions hose on the upper intake somewhere .i have seen this on the v-8 before as well .
i am not familiar with the ohc engine much as i have the pushrod ohv engine but the codes mean the same thing and i been there done that .
replacing you fuel pump will not rid you of these codes . not that it isnt good maintenance but dont expect those codes to go away .

good luck.

What you're showing besides the tensioner part are the upper and lower gasket, and yes they've been replaced.

The codes are for running lean. Usually the simple answer is an air leak, because theres too much air mixed in with the fuel mixture and the MAF can't adjust it enough. In my case, the car's running lean because it's not getting enough fuel. The fuel pump is only putting out 35psi instead of 65 and it's not holding pressure.

I'm not sure how you can say it doesn't need a fuel pump. Are you saying that the engine receiving about 50% of the fuel it needs isn't going to make it run lean?

 

[joe doe]

what i was saying is "if you have an air leak "replacing the pump wont help .

glad to see you replaced all the correct parts .as far as fuel pressure goes there are 2 different systems and pressures to look at .
there is a return type system and a returnless system and each one runs a different pressure .

 

[blue89bird]

what i was saying is "if you have an air leak "replacing the pump wont help .

glad to see you replaced all the correct parts .as far as fuel pressure goes there are 2 different systems and pressures to look at .
there is a return type system and a returnless system and each one runs a different pressure .

From what I can gather in 99 they were all returnless fuel systems and the regulator is built into the in-tank pump.

 

[blue89bird]

So I finally replaced the fuel pump. Hard starting is gone and the truck runs great.

The dreaded P0171/P0174 codes popped back up however. Car starts right up and idles great until it warms up. After it warms up however, the idle quality drops and it seems to bounce around 5-700rpm causing the steering wheel to shake. If I give it a little gas to hold it steady at 6-700 it smooths out and runs great.

Am I correct in thinking O2 sensors? It already has new intake gaskets, new fuel pump, cleaned maf and iac and a recent tune up.

 

[blue89bird]

Replaced the iac today, its probably 50% better. It only bounces/shakes when warm and in gear. If you put it in nuetral or park it runs great. When driving around its great, its iust when sitting in gear whn warm.

Any ideas?

 

[Bill MacLeod]

Had those codes pop-up last winter, thought it was caused by the lower intake gaskets. Did not change them when I replaced the tensioner.

My scangauge was showing an operating temp in the low 180's, I had changed the stat with a brand name some time earlier. So I forked out the extra $ for a Motorcraft stat, o/t returned to 190 plus and no more codes.

Not sure if this will help, but check the engine operating temp to see if the stat is working properly. I didn't have any drivability problems at the time, just the codes popping-up.

 

[buzz]

I would stop throwing parts at this and find a mechanic you can trust.

 

[Fiero Thomas]

i would stop throwing parts at this and find a mechanic you can trust.

x2