Upper/lower intake torque

[e21pilot]

With over 200K miles on my 92 4.0 Ranger, I was thinking it might be a good idea to check the intake bolt torque.

I have read that there are eight 10mm lower bolts to check but what is the torque spec for these? Also, when checking torque on an intake, I always loosen each bolt and re-torque it to spec so that nothing else moves -- I don't want to create a problem where there isn't one already. Not sure if this approach is recommended on the 4.0 or not.

What about the upper intake bolts? Does the upper intake often get loose as well? I think there are six, what type are these and what is the recommended torque?

 

[hank857]

http://www.therangerstation.com/tech_library/4_0-loose-intake-bolts.shtml

 

[Mazda]

As the owner of a 94 2.3L with over 300,000 I would leave it alone. Especially if you don't have any leaks. Wouldn't want to snap a bolt off. Just my opinion about the dilemma I got my self into.

 

[TxGasRacer]

1993-1997 4.0 ohv lower intake torque spec is step one 36 in-lbs , step two 72 in-lbs , step three 132 in-lbs ,step four 180 in-lbs and make sure you torque the lower intake manifold bolts in the correct bolt tightening sequence http://www.therangerstation.com/tech_library/diagrams/4_0-lo1.gif

 

[SenorNoob]

Why? If there isn't a problem leave it alone. Bolts UN-torquing themselves almost never happens on anything but race vehicles and older unbalanced engine designs (motorcycles).

 

[e21pilot]

I've been around engines long enough to know that it is sometimes best to leave well enough alone. I'm chasing a problem with the engine stepping down in RPM when returning to idle rather than smoothly lowering RPM to idle. One of the causes of this was listed as "vacuum leak" so I've been systematically looking to eliminate any potential leaks. For now, I'll look elsewhere and leave this one alone.

 

[SenorNoob]

I'm sure you have, but have you considered a sticky IAC?

 

[e21pilot]

Yes, I cleaned the original and it made not difference. Then I replaced it with a new Motorcraft one -- still no difference. Also cleaned the throttle body front and back but again, no difference. Not sure what other components are in the loop that would cause the stepping down of the idle.

 

[adsm08]

I would not mess with the torque on the lower intake. The heads and the lower intake are torqued together as a set on that engine, and it could be disruptive with that many miles.

 

[SenorNoob]

The heads and the lower intake are torqued together as a set on that engine

I don't think I've ever heard that before. It's a miracle I didn't cause problems then when I changed my lower intake gasket.

You know why they did that?