Problem: hi - low idle - hesitation 4.2 V6

Pulled some codes over the weekend
P0401 EGR
P0171 ox sensor - MAF
P0174 ox sensor

I need to look for any obvious vac leaks.

MAF was repl 45k mi ago - looked good but did a CRC clean on it --- no real improvement.

Looks like its going in the direction of cleaning the carbon from the intake plenum. Repl EGR. This was done by a shop about 45k ago and cleared everything up

Question ? I'm gathering info that the plenum gasket can almost always be reused ? Is that the case ? A new is only about $14. What's best ? Do I use any addl sealant with the gasket whether new or old ?

What's a good tool or method to run through the ports ?

Upon install of the plenum - torque the bolts to 8 ft lbs ??? What effect does a 3/8 x 6" extension have on a needle torque wrench ?

Thanks a lot.

 

Definitely look for vacuum leaks----these motors are known to develop them, especially a '99. You should have an IAC which can also be problematic although they will set a code most times.

If by intake plenum you mean the opening to the throttle then any sort of carburetor or MAF-specific cleaner should do quite well. I've run an old toothbrush through one on my '00 E250 5.4.

Not sure I'd ever advise re-using any gasket regardless what's claimed---it goes against everything I know about their function. $14 is nothing compared to the hassle it is replacing one failed due re-use; my thought is always err on the side of perfect is better.

Applying torque through a straight vertical (or in-line with the fasteners longitudinal axis) extension tends to have zero effect. This assumes the extension would fit squarely on the bolt heads, no angular attempts at tightening.

IF your spec indeed calls for 8 ft/lbs that's a task better suited to a torque tool calibrated in foot/inches. Its nearly impossible finding a ft/lbs wrench that fine in its calibration---I've never seen one capable of accurately reading values that low.

Anyway best of luck with your project---let us know how it turns out.

 

Hi Steve,
New gasket, always.

You can experiment with torque wrench effects easily. Use a nut/bolt clamped in a vise and check torque settings using various length extensions.

Are you sure about the torque spec? I found a spec for '97 to '00 that says 4.92 Ft-Lb (59 In-Lb)

Ford 4.2L-256ci-V6 Torque Specifications - TorkSpec - Knowledge for the Motorhead

That may not be your engine configuration but worth checking.
jim

 

Personally I don't experiment with torque settings---apart from very, very few uber-specific torque settings my tools are more than adequate for most any automotive job. I've always tried to place the torque wrenches measuring portion close enough and in line with the fastener so no worries I'm off by 50% or more of my settings.

I don't know about your engine nor its torque specs---I was merely talking in general about the general questions you posed.

 

A straight extension has no effects on torque, the offset ones do, they are used as torque multipliers, depending on how far they offset from the wrench, this I do remember from class. A lot of items are claimed, reusable, but since vans are hard to get at, I say insurance is the best policy, put a new one in, and 'Always' follow the torque pattern to insure that it seats even, don't tighten them all down in a row, I believe they are from the middle out.

 

Thanks all for the replies. Going to have to do a fix within a few days --- too much idle / break down now...

I'll get the new gasket. I have a manual, just need to review it about the torque, etc. Haven't used tourque wrench much.

Looks like new EGR valve, R&R plenum with new gasket ---- maybe a smoke test. Saw that on YT....

YT is great but I need the experience here.

Thanks for taking time out of your busy day to reply....

 

Be careful with testing for leaks, the doghouse being so enclosed, limits what you can see, along with the fan blowing everything back while running.

 

I did that exact job in springtime 2013. If you can search my posts and find it you'll see lots of details. LOTS of details.

Mine was exactly as your post described but with the additional problem of misfire codes. The misfire(s) were caused by 5of the 6 EGR ports being clogged.

The lean codes and bad idle were caused by bad isolater bolts and intake gasket.

Find my old posts on this. You'll find it useful. And if you want to talk I'll give you my phone number. There's a few more things ok my mind that I don't have time to type right now.