Solved P0171 code, fuel pump? thoughts comments?

99 EB 5.0, has started hard for a while, I really only drive it maybe 1000 miles a year, but I just sold my GTI, so the explorer is my DD until I find a replacement.
it starts hard, has for a long time, but if I cycle the key a time or 2 it hasn't been a problem the CEL just popped on and it Is a P0171 seems to be a vague code I have cleaned the IAC valve and MAF. it has a newer Fuel filter and plugs and wires.
the hard starting has not changed it was the same before all of the things were done.
it has 156K miles.

sometimes when I start it it will stumble and struggle to run for a few sec. then it recovers and runs fine.

I checked the FP and it was good, I don't remember the PSI at the moment but it was like 67 at idle or something like that.

I don't know how responsive the cel light is, but it seems to pop on when I am just driving slow

I am thinking maybe I need to just do a pump?

if so, are there recommendations on one to buy and who has the best prices?

or a brand to stay away from?

a quick look showed advance auto has a motorcraft pump assembly but it was $400+
I would rather just put in a whole assembly, even though it is more money.

recommendations or suggestions?

if it was the fuel pump I would think you'd see P0171 along with P0174. sounds like it might be a vacuum leak effecting only one bank. BTW, around 65 PSI of fuel pressure is fine.

any ideas where to check? also I have just replaced the PCV with a motorcraft one

a smoke test is the best way to find vacuum leaks. did you check the PVC grommet and hoses when you replaced the PCV?

I didn't check the grommet, but the PCV balve did pop in fairly easy, it is impossible to see and a Pain to reach to do the PCV maybe a better idea to pull the upper intake?

should I just buy a new PCV grommet? how does one go about a smoke test?

unless you want to build your own smoke generator, easier to take it some place that has one. basically you want to burn mineral oil and force the smoke into the engine (through any vacuum port). if you see the smoke escaping from somewhere, that's a vacuum leak.

as it's impossible to see, and hard to get at, you might want to hold off on replacing the PCV grommet until after the smoke test.

koda2000 said:

if it was the fuel pump I would think you'd see P0171 along with P0174. sounds like it might be a vacuum leak effecting only one bank. BTW, around 65 PSI of fuel pressure is fine.

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I have both codes and none of the mechanics I have taken the truck to has mentioned the fuel pump. They all suspect vacuum leaks. If it were the fuel pump would the rough idle go away after warming up?

PAExplorerXLT said:

I have both codes and none of the mechanics I have taken the truck to has mentioned the fuel pump. They all suspect vacuum leaks. If it were the fuel pump would the rough idle go away after warming up?

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a weak fuel pump, or even a clogged fuel filter, could conceivably cause the P0171 & P0174 lean codes, because air is entering the engine, but there isn't enough fuel for ideal combustion. as you have the SOHC motor and the idle improves once the engine warms up, your issue is most likely vacuum leaks, probably caused by the upper/lower intake gaskets/O-rings. this is a very common problem with the SOHC motor. my SOHC has started doing the same thing now that it's gotten cold, however it clears up almost immediately once the engine is started and has not thrown the codes yet. I will look into it in the spring (assuming the engine hasn't blown up by then, or the trans quit). if you can't tell, I am not a fan of the SOHC engine. mine was rebuilt, so at least the timing chains aren't making noise yet.

I just pulled the codes since the CEL came back on and it is a p0171 and a p0174 now.


so what does that change?

I had both the PO171 and P0174 codes (banks 1 and 2 lean condition) and they would not clear. It popped up just after I changed my fuel filter. However it turned out that the actual problem was a vacuum leak caused by the intake manifold gasket (upper). Car runs so much better, quieter and gas mileage was drastically improved. Cost me $60 to $70 dollars all in to do the work myself and took about 3.5 to 4 hours because I was just getting over a bad cold. Its really only a 2 to 3 hr. job.

Rich- said:

I just pulled the codes since the CEL came back on and it is a p0171 and a p0174 now.


so what does that change?

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if you're getting both codes it just means that the vacuum lean is getting worse and is now effecting both banks of the engine. it really doesn't change anything. these codes indicate air is getting into the engine somewhere past the MAF sensor (hence "unmonitored"). this leans out the fuel/air ratio, increase idle and combustion temperature. a smoke test is the best way to find out where the unmonitored air is getting in, as there are MANY places this can be happening from.

- any and all rubber vacuum hoses
- PCV grommet, elbow, hoses
- brake booster hose, or the brake booster itself
- vacuum ball reservoir
- HVAC controls and actuators
- intake manifold upper or lower gaskets/O-rings
- evap system (throws different codes)

as you can see, that's a lot of stuff to check and you might miss something. that's why forcing smoke into the engine is a really helpful tool. plus as I said earlier, a lack of sufficient fuel, due to a weak pump or clogged fuel filter might also cause these codes. you need to properly diagnosis the problem rather than throw money at it. even if a smoke test costs you $100 it's worth it to find the problem.

thanks, I will check into the smoke test., but I also have hard starting and it seems to be lacking power.

Rich- said:

thanks, I will check into the smoke test., but I also have hard starting and it seems to be lacking power.

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vacuum leaks can cause both these symptoms.

I called a local shop that handles all of our work trucks, talked about it with him and he said that they have a smoke machine and they will have a look at it Monday.
my mpg is crap, maybe 12-14 combined with city/hwy ive even been easy on it..

maybe I am just too used to driving a 30+mpg GTI

Rich- said:

I called a local shop that handles all of our work trucks, talked about it with him and he said that they have a smoke machine and they will have a look at it Monday.
my mpg is crap, maybe 12-14 combined with city/hwy ive even been easy on it..

maybe I am just too used to driving a 30+mpg GTI

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well, you're never gonna see 30+ mpg out of an Explorer. my v8's typically average around 17 and the best I've ever managed (under ideal conditions) was 23+ hwy. the v6's might do slightly better, but not much.

koda2000 said:

well, you're never gonna see 30+ mpg out of an Explorer. my v8's typically average around 17 and the best I've ever managed (under ideal conditions) was 23+ hwy. the v6's might do slightly better, but not much.

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oh I know, I am still in shock I think at going back to driving this at how terrible the mpg seems in comparison

well, it was the fuel pump.
took it in to the shop today, and they said it was only 35psi and when tou turned off the key the check valve was bad and it dropped the line pressure to 0 which was the hard starting.

eneded up with an entire pump assembly for $320 and $150 to install it,.. I figured f-it just do it. for the $150 labor it saved me hassle and frustration.

fires right off, and feels like it gained a bout 50 hp.

hopefully the mpg goes up, I filled up and avg. was 14mpg with 50/50 hwy/city

Wise choice. Half way through the installation you’d be happy to pay someone $300 to finish it for you.

PAExplorerXLT said:

Wise choice. Half way through the installation you’d be happy to pay someone $300 to finish it for you.

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well, if you've got the money and not the time (or skill) to do it yourself, I guess it's worth it to pay that kind of money, but I just changed 2 fuel pumps in the past week for a total cost to me of around $165, pumps, strainers, filters and ancillary parts. granted I didn't need the assemblies. the satisfaction of doing it myself (and saving $775) - priceless.

koda2000 said:

well, if you've got the money and not the time (or skill) to do it yourself, I guess it's worth it to pay that kind of money, but I just changed 2 fuel pumps in the past week for a total cost to me of around $165, pumps, strainers, filters and ancillary parts. granted I didn't need the assemblies. the satisfaction of doing it myself (and saving $775) - priceless.

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Changing a fuel pump in December in Georgia is a whole different world than changing one in December in South Dakota.