I have cleaned the MAS thanks to the posts I've read on this board. I'm new to posting here, but I've been to this site many. many times. You guys are great. I have a 98 F-150, 4.6L 4X4, K&N filter w/ homemade FIPK(thanks again) and 33"x12.5" tires. The thing runs great and sounds great too with the Flowmasters.

The MAS cleaning killed the pinging completely. However, the check engine light comes on every time my wife drives, 3X now. I drove it for two weeks this last time after resetting it with no problems. She drove it yesterday and bingo there it is again.

Does anyone know why this is happening? I am assuming the short shifting is doing it, she shifts before it goes over 2000 rpm. I have told her since to give it more rpm before shifting. Is this an indicator that an oxygen sensor is bad or what?

Maybe I just need to give her driving lessons. LOL

Thanks again, you guys rock!

 

FordOkie,

Are you sure it is your wife's driving that is setting off the codes? Can you get the code read? It could be coincidence.

Regards

Jean Marc Chartier

 

I'm not 100%, but I put at least 250 miles between resets and I have never experienced a problem. It is a manual, which she has in her Acura, but she did tell me she shifts early in my truck to save gas.

I haven't reset it yet. I'm going to try to get to the auto parts store tomorrow and get a reading. I will post it as soon as I get it.

Other than the pinging, which left after MAS cleaning, it runs great. With 117K miles, I'm sure something else needs to be cleaned or replaced too.

 

Okay,I got a code P401 from Autozone.

All hoses are on and this problem only presents itself when the wife drives.

Do I need to clean it out?

Suggestions and instructions would be greatly appreciated.

 

thats an easy fix! just dont let your wife drive your truck anymore.

 

P-0401 is generated due to insufficient EGR flow..
usually the DPFE sensor is the cause for this, and in few cases,
is the EGR valve itself.. But without being there, it's hard for me to tell you what is exactly triggering the CEL.

Hope this guides you in the right direction!!

Good Luck!!

FordMasterTech

 

You let your wife drive your truck?

 

I'd try cleaning out the EGR passage in throttle body before buying any parts. The EGR passage on the 4.6 is very prone to plugging with carbon. IMO this is a much more common problem than the DPFE sensor or EGR valve, and costs almost nothing to repair (a couple of gaskets at most). The subject has been well covered here. Try a search.

 

hmm..i had one yesterday, well it came up twice, 402.....replaced the gas cap, and bam, its gone*cuz of the reset* but i've started the truck a million times since yesterday, soo. yeah. if it comes back again, what the hell is it? becuase I've had this before, replaced the cap, but i think the 2nd cap *not the 3rd, which i just bought* was bad. any info for me?

 

402 is the opposite code of 401 which means too much flow in EGR system. Most would just assume it's the EGR valve sticking which could be the wrong guess, more than likely from what I have seen, heard and read this usually indicates a bad DPFE. The 401 code usually indicates the blockage of the passage's. The newer (as in the 00 or 01, 02 trucks) DPFE's are plastic and I have been told are crap. You can test the DPFE with a multimeter or replace it for less than $75