P0171 P0174 - Too Lean - Explorer Sport '99 SOHC

LuketheDuke · June 27, 2010

I got this car in january after it had sat for 3-4 years. It drove like a champ until the transmission went out. After having it rebuilt it drove like a champ again until the check engine light came on. It always idled a little rough when first starting it in the morning but i figured it was because it was pretty cold out. The light came on and it was spitting out the Too lean on bank 1 and bank 2 codes. It still idles rough when first starting it and it also occasionally hesitates when starting from a stop or from at slow speeds. It jolts occasionally at these times as well. I understand this could be a vacuum leak, bad MAF sensor, or other things. I have taken the MAF sensor off and cleaned it. I have also sprayed starting fluid around the hoses to try and detect a leak somewhere but I haven't found anything yet. Any ideas?

saewoody · June 27, 2010

If I recall correctly, this could be your intake manifold gaskets letting air by. Good luck.

Rudy602 · June 27, 2010

LuketheDuke said:
I got this car in january after it had sat for 3-4 years. It drove like a champ until the transmission went out. After having it rebuilt it drove like a champ again until the check engine light came on. It always idled a little rough when first starting it in the morning but i figured it was because it was pretty cold out. The light came on and it was spitting out the Too lean on bank 1 and bank 2 codes. It still idles rough when first starting it and it also occasionally hesitates when starting from a stop or from at slow speeds. It jolts occasionally at these times as well. I understand this could be a vacuum leak, bad MAF sensor, or other things. I have taken the MAF sensor off and cleaned it. I have also sprayed starting fluid around the hoses to try and detect a leak somewhere but I haven't found anything yet. Any ideas?

The 4.0 SOHC has a problem with the intake manifold gaskets. Use search feature for such topics as 01M01, 00M12, intake manifold gaskets, and timing chain tensioners. The old gaskets fail and allow extra air to be sucked in causing a "too lean" condition and rough idle while cold. The timing chain tensioners are another problem you can solve at the same time. I just became aware of these issues, myself. Lots of info and pictures on these topics.

Xplorer82 · June 27, 2010

im going to have to say intake gaskets as well. here is the thread that i followed. (i skipped the tensioners part.)http://www.explorerforum.com/forums/showpost.php?p=487634&postcount=33.

LuketheDuke · June 28, 2010

Thanks very much. I forgot to mention earlier that 3 of the 6 spark plugs were changed however, the passenger side plugs were to difficult to get to at short notice so it is running with 3 good ones and 3 not-so-good ones. However, most of the trouble began before this...is it just me or are these engines not so simple to work on? Also, how much does an 00M12 Kit usually run you?

Xplorer82 · June 28, 2010

LuketheDuke said:
Thanks very much. I forgot to mention earlier that 3 of the 6 spark plugs were changed however, the passenger side plugs were to difficult to get to at short notice so it is running with 3 good ones and 3 not-so-good ones. However, most of the trouble began before this...is it just me or are these engines not so simple to work on? Also, how much does an 00M12 Kit usually run you?

i bought my gasket set for like $25'ish (i only replaced my gaskets, no tensioners). im not to sure on the whole kit.

the best way to get to anything on the pass side is to take the tire and splash shield off and go from under there. makes things so much easier. (now that you know, go change them other 3

)

LuketheDuke · June 30, 2010

Well, I have the gaskets coming in from autozone tomorrow morning first thing. My question now is do I absolutely need to use a torque wrench?

ncranchero · June 30, 2010

If your 99 4.0L SOHC is the same as a 01 4.0L SOHC you'll find the front PCV elbow to be cracked and causing your problem. If yours is like this photo then check it before you tear stuff apart. The crack will be on the bottom, that's on the lower hose.

KCV190 Motorcraft

Rudy602 · June 30, 2010

LuketheDuke said:
Well, I have the gaskets coming in from autozone tomorrow morning first thing. My question now is do I absolutely need to use a torque wrench?

I'd say you should use a torque wrench, the manifold is plastic, the bolts are thin, and I think they're going into aluminum. Read the thread by 2000streetrod and buildup the torque gradually and evenly starting in the middle and working outward.

bantonich · June 30, 2010

if you are a DIYer, then you will want torque wrench. I use mine all the time.
If you rarely work on cars, then you are probably unfamiliar with how much 15-19 lbs
of torque is.
Autozone should loan you one if you dont want to buy one

LuketheDuke · June 30, 2010

Today I took everything apart, replaced the gaskets, started torquing the bolts back in on the lower gaskets when one of the bolts broke while it was inside the hole. I decided to go ahead and continue, and I put it all back together. It started right up and idled fine. I don't know whether or not it idled fine because of the gaskets or if it was because it had been run 4 hours prior to it. Anyways, I took it out for a 10 minute drive and immediately noticed the puttering again as well as the lack of acceleration power. Doesn't seemed to have been fixed. Could it have been that broken bolt?

By the way ncranchero, I couldn't find the hose from the picture. Where around the splash shield is it?

saewoody · June 30, 2010

I would say that the broken bolt could be a possibility. If there is air getting sucked in through a small gap because it is not torqued down enough then it would be similar to having air get sucked through a bad gasket.

LuketheDuke · July 1, 2010

I had taken the MAF sensor and cleaned it with denatured alcohol and brake cleaner...could it just be a bad sensor?

ncranchero · July 1, 2010

LuketheDuke said:
By the way ncranchero, I couldn't find the hose from the picture. Where around the splash shield is it?

Splash shield ??? What you're seeing in the photo is the radiator hose, MAF cover and corner of the intake manifold ........ If you just replaced the intake gaskets and didn't see the hose then yours must be different from the '01.

rickybobby · July 1, 2010

the pcv elbow should be in the same place on a 99, and is a very common problem. If you dont replace the broken bolt it will at a minimun create a problem down the road.

LuketheDuke · July 3, 2010

Well, I believe I found the problem. I pulled the fuel filter just to see if maybe it was a bit clogged and immediately, a rusty mixture of fuel and gunk game out. I tried to blow through the flow end and no air could get through. I replaced the fuel filter and immediately, power was restored. I'm going to reset the check engine code and see if it comes back on. If this was the problem (which I think it was), at least I fixed my idle issues.

ThePhoenix · July 6, 2010

Did you replace the upper and lower intake manifold gaskets or just the upper?

P0171 P0174 - Too Lean - Explorer Sport '99 SOHC

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