1998 e150 5.4L p0171 p0174 service engine soon light
 

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

1998 e150 5.4L p0171 p0174 service engine soon light
 

Hi Ed and welcome to FTE :)

Both codes you have mean the engine is running too lean and the PCM cant inject enough gas to compensate, or it thinks it can't.
Have you had your fuel pressure checked? Low fuel pressure could cause your problems. Possibly a weak fuel pump or bad regulator.
Trying another MAF would be a good idea too if you could find one to try without having to buy a new one.
It sounds like you've done a good job of checking for vauum leaks but you might want to take some spray carb cleaner such as Carb Medic and, with the engine idling, spray it all over where the intake joins up with the heads, on any vacuum lines etc. If the idle changes at all when you spray the Carb Medic you've found a leak.
Let us know what you find.

1998 e150 5.4L p0171 p0174 service engine soon light
 

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.

By the way, I noticed on the obdii web page that each of the manufactures has extra diagnostic codes. They have them listed. In addition, the reader which reads those was very expensive compared to the generic obdii reader.

No more pinging and the engine runs very well again!

1998 e150 5.4L p0171 p0174 service engine soon light
 

Sounds good :)
Thanks for letting us know what you found.