The "Check Engine" light was turned on yesterday on my '98 Expedition EB. I got two codes at the same time:

1. P0171- System Too Lean (Bank 1), and
2. P0174- System Too Lean (Bank 2).

I know either one of these codes can mean something is wrong with air intake, fuel system, or O2 sensor. But if these two codes show up together, we should be able to eliminate something, right?

For example, if Bank 1 and Bank 2 use their own O2 sensor, then since we know it's very rare for both sensors fail at the same time, it can't be the O2 sensors.

Could anybody give me some hint here?

Thanks!

 

I had the same codes on mine and it eventually began to idle rough (although not right after getting the CEL). It turned out being the PCV valve line where it connects to the rear of the intake manifold. Just reach around the back of the engine with it running and feel around and check if it is leaking.

 

I just checked and found a hole on the elbow there. You are a genius!

If I am on the right track, this PCV line has an elbow at the engine rear end side. The line side is about 0.5" diameter and the engine side is about 0.75". This elbow is a rubber part and I found carbon debris right at the turning point where it broke. I first found a little hole there and when I tried to pull it out, it broke almost completely. I found the engine can't even idle without this connection.

What did you do to fix it? If you bought a new piece from Ford, do they have a new design for this part? Apparently it's another faulty design from Ford and I just wonder if they have a new design which they will call "heavy duty" part as usual. Do you have a part number?

By looking at the broken part and its location, I really think it should be made of metal. The temperature there is very high because it's too close to the firewall and all hot air goes there and stops there.

I will try to buy one from Ford dealer tomorrow.

Thanks a lot!

 

WhyFord,

I just replaced it with a new Ford line (you have to replace the whole assy). I did toy with the idea of making my own for the same reasons that you stated. I still have my old one and if I have a problem with the new one I will then build/modify my own.

I'm glad I was able to help!

Britt

 

Would you happen to know the part# for the assembly?

Thanks

 

I just bought the part from a Ford dealer and the part number is: F75Z-6C324-JA. There are two different part numbers: one is non-heated (this one) and the other one is heated. Since the dealer only got this one, I just took it. I will try tonight to see if it will fit. If it doesn't, at least I can use the elbow from it. That's the only part broken on my truck anyway.

Thanks!

 

Whyford

I also had the identical pair of codes kick out of my Expy. I was getting ready to replace the entire EGR system, valve, relays, etc. plus PCV components to the tune of almost $300 in parts from the dealer.

I caught some tips from this forum on other possible causes. One of which was simply a dirty MAF. I simply pulled the MAF out of the black intake and squirted a bunch of brake cleaner in it. I did notice before I cleaned the MAF that there was some lint-like looking goobers on the heated wire in the MAF. Long story short...no more codes, no more rough running...going on 6 months now.

My two cents...

Good luck this can get frustrating.

 

I replaced the broken PCV line elbow with the one from this assembly I bought from a Ford dealer (F75Z-6C324-JA). My truck should use the "heated" version of it, but the dealer doesn't have it in stock. The heated version has a three way at the PCV valve side to use the engine coolant heat to warm up the intake air, I guess. I also used the new PCV valve from this assembly.

After I put everything back together and installed it on my truck, it runs like new now. I cleared the engine codes and they never come back again!

Thank everyone for your support in pin pointing this problem. I spent only $20 for an otherwise $500 dealer job.

I love this place!

 

I've had the same codes and subsequent check engine light for about a year now. I've been fooling with it on and off. I think I finally got it. The predominent problem seemed to be the leaky PCV line elbow. That wasn't the case with mine......it seems to be solid. Mine I believe was the dirty MAF sensor. I decided to replace it ($170 from Ford) and eliminate all doubt. I could tell right away that it ran smoother at idle. No more hesitation when accelerating either. If the code is going to come back it will likely be in the next few hundred miles or so, but I don't think it will. Thanks for everyone's advice and feedback. It is extremely helpful.

 

I am so glad that I did a little research and found this tread. You guys save some $$$.

My PCV elbow was also the cause of my "check engine" light. My father-n-law ran the codes and got the service codes 171 and 174.

Had you guys not been so precise, I am sure that I would not have found the 2nd elbow at the back of the intake. And Yes, it did have a hole in it and it broke in two while removing it.

I am very frugle so I went to a auto store and got a Motormite PCV elbow. They are in the red package marked "Help". It cost me $4 bucks. I am sure that Ford would have charged me over $200 in unnecesary parts and labor. Thanks again.

 

Hi everyone,

I have a 5.4L 1998 clubwagon (e-150). After searching forever on the web, I found that the expedition seems to have the same engine and problem. I read this forum and checked most everything recommended. So, can any of you guys help me out? Here is what I have done:

1) The codes P0171, p0174 first showed up in Dec of '02 (service engine soon light).
2) It seems to come on when accelerating (like to get onto an on-ramp for the highway) and with the van loaded with cargo.
3) I have replaced the fuel filter, reset the light, it came back.
4) I replaced the rear 02 sensor behind the cat converter and it went away for over 3000 miles. Then the light came back.
5) I replaced both of the 02 sensors just off of the engine and it came back right away (again while accelerating).
6) I replaced the PCV valve, ran it hard for a short while on a test drive, it stayed off for about 75 miles. Then I left for a trip and it came on right away (while accelerating onto the highway).

When the light comes on with these codes, I get pinging during slight acceleration (up hill) on the highway. When I reseat the PCV valve, it seems to go away for a short time.

I have checked all of the tubes/elbows, etc. from the PCV and they look fine, no cracking like some of you have seen.

I checked the MAS and it looks clean! I did put some silicon on the MAS wire casing gasket into the air intake tube to make sure it is sealed with no leaks. Does anyone have any ideas on what I can try next?

I just reset the light after reseating the PCV valve and putting the silicon on the MAS wiring to seal it. So there should be no air leaks from that. I am certain that it will return. It seems to come on when I have the van loaded down with people or cargo. I haven't had it loaded when test driving it. But right now, the light is reset (off) and no pinging. So, in anticipation of the light returning with these codes, can any of you let me know what has worked for you as well? My next step is to swap the MAS.

I would appreciate any thoughts that you have on this.

Thanks,
Ed

 

I found what was causing my problem in a Windstar with a 3.8 ltr. It was the grommet for the PVC valve. It was causing a vacuum leak cause both banks to lean out. A $2.00 fix for something the dealer wanted to fix for 275.00. Look for vaccuum leaks folks. It is a sure way to cause a lean condition. By the way if you think it is a O2 sensor, think again, They are working fine. After all it detected the lean condition right?

 

The light came on shortly after I posted this question. I checked thoruoghly for leaks as suggested with carb cleaner while the engine was running. Also listened for vacuum leak noises. It ended up being the Mass Airflow Censor. Looking at the old one, one of the 2 wire (resister looking pieces) was black, the other silver. When I purchased the new part, both of the pieces of the sensor were silver.

The part was easy to replace and I purchased it on line. Locally the dealer wanted $199+$75 core deposit. The core deposit is refunded when you return the old core. I found it on-line for $154 (plus the same deposit deal). I had to mail back the old core, so the total was $160.

No more pinging and the engine runs very well again!

 

You may want to be careful about getting silicone near the MAF or intake.

I know on my *other* car the manufacturer has issued a TSB warning that silicone can kill it.

 

I wish I would've found this thread $240 ago. I stumbled on this site after I had already changed my fuel filter, MAF sensor, my two O2 sensors on my 97 Expy and decided to change the PCV valve as a last resort before giving the truck to Ford. When replacing the PCV valve, I broke that little line at the rubber boot at the rear of the manifold to the PCV valve. I did a search of the web for something and found this thread which listed my problems to a "T". Trouble codes P0171 and P0174...

That $33 part from Ford fixed all my probs and my O2 sensors and my MAF were probably not bad after all.

Thanks for your headaches helping to solve mine,
Rich