Piston Slap: A Tribute to the Mariner’s idle Escape? (PART II)

radiator hose Shutterstock User's 7th Child Study

We had two updates to a previous Piston Slap this weekend, amazingly within two hours of each other. First let’s hear the OP:

Sundvl76 TTAC Commentator writing :

Sajeev, reporting:

This may interest you, if only to add to your diagnostic toolbox; my experience certainly can’t be unique – several comments below your post also suggested that the motor mount(s) were the problem. I discussed this more recently with a well-known Wrench pro, who also said mounts can be expected to head south after about 80,000 miles; he suggested using a padded jack to raise the engine slightly for a while when I detected “rough” idling (the oil pan on this vehicle, and possibly all Duratec engines, is cast iron embossed aluminum). Bingo! The vibration stopped when I did that.

I have now replaced the large mount on the passenger side of the engine bay and can report that the vibration is no longer present. But, there is an added price to this story: for the last 25-30,000 miles, I also chased a screeching noise that would occur, again more prominent in cold weather than hot weather, at any speeding stop sign/traffic light. I would have bet big money it was the rear suspension, and I actually went as far as replacing 3 of the 4 rear control arms (they’re pretty cheap and easy to replace), to no avail. Replaced motor mount – squeak magically gone!

There’s nothing fancy about this vehicle – my wife drives it 80% of the time and it meets her needs, and I really don’t care, but these nagging issues really got me thinking about throwing it away. A whole new attitude now – it’s going to stick around for a while yet! Thanks for your help and thanks for reading this. I really appreciate your posts.

Sajeev answers:

Great ! I’m glad to see that my initial in-office diagnosis paid off. All it takes is a fractional difference in the mounting height of the new one to cause this problem. Maybe a millimeter, maybe less! You can’t look at this and know for sure.

I’m totally digging the padded floor jack into the oil pan thing. Maybe the crankcase needs a boost to work here, not just old-school sheet metal business. But maybe all it takes is a little movement in one corner (i.e. not the big flat part of the pan) to show that the bad idle is in fact engine mount vibration. Or put a long board on the jack so the weight is distributed across the board, corner to corner.

Anyway, I’m glad to see that you enjoy your trip much more now. It’s hard not to love him after you’ve “dirty” your hands, arms, legs, and even your mind during a successful diagnosis of a seemingly impossible problem!

Later Rein writing :


Greetings! I really appreciate your beautiful column and your blog. Keep up the good work! As for the bad idle the reader was looking for help with on their 2005 Mariner, I thought I’d jump in after long experience with the Ford/Mazda Duratec family of V-6s, especially the 2001-2007 Tributes and Escapes. Also, my daily driver is a 2003 Tribute with 199,000 miles. I’ve found that the V-6 idle problem, after all the usual culprits have been unsuccessfully investigated and/or fixed, could be either of two things: a bad DPFE sensor or intake gaskets baking.

These V6 engines have a manifold on top that is bolted to a cam riser, which in turn is bolted to the engine. There are six joints where each component meets the other, and unsurprisingly, after 100K, all six joints between the camera and motor have hardened by time and heat (in much worse condition than the six gaskets from chamber to engine). multiple, which might still seem malleable). The lower seals harden and begin to suck in air, and this condition shows up most visibly in poor fuel economy and poor idling. I had excellent results replacing all intake gaskets (full intake gasket set required) and all small vacuum hoses, cleaning the MAF sensor (using MAF sensor cleaner, not carb cleaner), and a air flow ; in most cases, slow motion of the showroom floor is restored.

These engines also seem to prefer Motorcraft platinum spark plugs; I’ve tried other plugs in a pinch or on sale, but the Motorcraft ones produce the smoothest idle and best fuel economy for me. Of course, if the DPFE sensor has never been changed, that’s a good idea. This component is also exposed to high operating temperatures. Mine did 140,000 miles before it failed, but I saw them go late…and late. You never know with these. Finally, my last fleeting thought on the subject: two half inch vacuum tubes on the T of the large air intake tube (just past the MAF sensor housing) and each connects to a grommet on the back of each valve cover. These grommets deteriorate from heat and oil contact and fail over time, resulting in a vacuum leak that starts slowly but quickly worsens. These should also be checked and replaced if they are soft and sticky.

I hope this information helps someone.

Sajeev concludes:

Thanks for write! I thought a bad DPFE would throw a check engine light (CEL)…because that’s my experience on my ’95 Mark VIII. And boy was it a fun sensor to replace on the MN-12 chassis! But I digress…

Rene’s stellar rating of the Duratec V6 is something all long-term car owners should be aware of: dry seals and rubbery vacuum lines that get brittle or rubbery. And not just the usual suspects you see with a quick look under the hood, there could be gaskets you wouldn’t even consider unless you have the proper service manual and/or your forum information specific to your model. I promise your eyeballs won’t find all the hidden gaskets and bits of rubber.

[Image: Shutterstock user 7th Son Studio]

Send your questions to [email protected]com. Don’t skimp on the details and ask for a quick fix if you’re in a hurry… but be realistic and use your make/model specific forums instead of TTAC for more timely advice.

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Source : thetruthaboutcars.com

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