F150 4.2l code p1151 p1131 problem
 

Hello Everyone...I have a problem I can't figure out. My truck's service engine light is on and giving me a p1151 and p1131 code. The only thing I've noticed it doing is occasionally the rpm's will bounce between 800 and 1100 and a stop light. That, and the gas mileage isn't what it should be. I'm averaging about 13mpg. Has anyone else had a problem with this? There's a TSB about replacing the upper intake gasket, but before I tear into that, I just wanted to check and see if anyone else has had this problem. I just had a new camshaft synchronizer installed, but I'm pretty sure it was done correctly. He balanced the motor to Top Dead Center and everything. Let me know if any of you have any suggestions. Thanks ALL!!!

<TABLE><TBODY><TR><TD vAlign=top width="100%">You need to replace the upper intake gaskets and bolts with these updated parts. <TABLE cellSpacing=0 cellPadding=3 border=1><TBODY><TR><TD class=NOBOTTOMBORDER align=left>1L3Z-9H486-AA</TD><TD class=NOBOTTOMBORDER align=left>Port Gasket</TD></TR><TR><TD class=NOBORDER align=left>3F2Z-9S479-AA</TD><TD class=NOBORDER align=left>isolator bolt</TD></TR></TBODY></TABLE>
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I replaced those parts, and still no change. Truck idles rough when cold and is getting 13-14 MPG average...not good. Did you have this problem with your truck?

What year is your truck?

2002 F150 4*4

Ive got the same codes dude and autozone sold me a new mass air flow. Im going to put it on tonight.

No luck with the MAS.

sorry to revive and old thread but did you ever get your problem corrected ? My engine light just came on today and threw a P1131 as well.

thank you,

Jason

sorry to reply two years later, but no I never got it fixed. It didnt seem to matter really, still runs good. It will idle funny when cold but other than that it is still good.

Check your PCV elbow/line

Codes 1131/1151 are the same code but for both banks.
Codes 171/174 are also the same codes.
They tell you the PCM has shifted the fuel tables out of limits trying to 'correct' for a lean or rich condition caused by some leak in the intake system.
Air leak anywhere!
Could be a hose after the maf, the throttle body being loose, dip stick or it's pipe allowing air in, low fuel pressure, excessive fuel pressure, PVC, vapor recovery, electrical corrosion in the OX sensor harrness plugsups.
Seeing a rough start tells you there is upset in the system with the fuel being leaned out from the problem.
Unless you go over all the areas by test or check, it will not go away.
It is not the MAF meter nor OX sensors.
These parts are before the air leak and after the leak.
Good luck.