From: Scott Dorsey on
CWLee <cdubyalee(a)post.harvard.edu> wrote:
>
>It took almost 2 years, and $1,400, of replacing/repairing
>one thing another until the "upper and lower intake manifold
>gaskets" were replaced. The mechanic tried that after
>allowing butane or propane to be released in various places
>as the cold engine was idling, and the fact that the engine
>speeded up when the butane/propane was released in a certain
>place suggested to him that there was a leak there, and that
>the leak was allowing the butane/propane to be sucked in and
>burned with the gasoline. His theory was that this leak was
>only there when the engine was cold, and that when it warmed
>up the metal expansion closed the leak; when the engine was
>cold, and the leak was there, additional air was being
>sucked in and diluting the gasoline/air mixture so much that
>the missing and stumbling was being caused.

This is the standard procedure for finding vacuum leaks of all sorts. And
if you encounter rough running problems that seem random, one of the first
things to do is to start looking for vacuum leaks.

>(What I'm reporting here is my experience, and what my
>mechanic told me. I have no automotive skills, and thus
>offer this only for consideration.)

It is an excellent offer, though.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
From: Ulysses on

"CWLee" <cdubyalee(a)post.harvard.edu> wrote in message
news:KsGdnV3X6ImgXCzWnZ2dnUVZ_i2dnZ2d(a)earthlink.com...
>
> I had the same set of symptoms on a '99 Explorer.
>
> It took almost 2 years, and $1,400, of replacing/repairing one thing
> another until the "upper and lower intake manifold gaskets" were replaced.
> The mechanic tried that after allowing butane or propane to be released in
> various places as the cold engine was idling, and the fact that the engine
> speeded up when the butane/propane was released in a certain place
> suggested to him that there was a leak there, and that the leak was
> allowing the butane/propane to be sucked in and burned with the gasoline.
> His theory was that this leak was only there when the engine was cold, and
> that when it warmed up the metal expansion closed the leak; when the
> engine was cold, and the leak was there, additional air was being sucked
> in and diluting the gasoline/air mixture so much that the missing and
> stumbling was being caused.

Just curious, but did you have intake manifold gasket leaks and NO coolant
loss or white smoke at startup? I'm having trouble imagining a manifold
gasket leak without coolant going somewhere, either inside the engine or
outside. Unless it was ONLY the upper gasket that was leaking. Seems kinda
unlikely.

>
> (What I'm reporting here is my experience, and what my mechanic told me.
> I have no automotive skills, and thus offer this only for consideration.)

Yea, well, if it wasn't for Hayne's and this newsgroup my Explorers would
have been in the junk yard many years ago.


>
> Best regards to all.
>
> ============================
>
> "Ashton Crusher" <demi(a)moore.net> wrote in message
> news:f139q5pqoneubqpu8066a75eamlufajvm3(a)4ax.com...
>> 92 Ford Explorer 4.0L OHV V6 130K miles, 10K on double plat plugs,
>> nearly new plug wires. O2 sensor was replaced about 40K ago
>>
>> Sometimes Runs rough when first started. Not just first start of the
>> day, but even when warmed up and then shut down for 15 minutes it will
>> often run rough initially like one cylinder is missing.
>>
>> Roughness usually goes away after it's warmed up but lately it's
>> started to have a bucking/missing/popping under light acceleration.
>> Giving it more gas usually smooth's it out. It will run on up to
>> redline and shift into the next gear and has no problem running up to
>> 90 mph. So unlike what I think of as the typical 'worn out plug"
>> misfire that shows up at high rpm and high load, this show up at
>> medium rpm light to medium load.
>>
>> It has not turned on the check engine light
>>
>> Any ideas?
>>
>> Things I'm thinking it might be..
>>
>> water in gas
>> bad gas
>> bad injector(s)
>> bad coil
>


From: Ulysses on

"Ashton Crusher" <demi(a)moore.net> wrote in message
news:f139q5pqoneubqpu8066a75eamlufajvm3(a)4ax.com...
> 92 Ford Explorer 4.0L OHV V6 130K miles, 10K on double plat plugs,
> nearly new plug wires. O2 sensor was replaced about 40K ago
>
> Sometimes Runs rough when first started. Not just first start of the
> day, but even when warmed up and then shut down for 15 minutes it will
> often run rough initially like one cylinder is missing.
>
> Roughness usually goes away after it's warmed up but lately it's
> started to have a bucking/missing/popping under light acceleration.
> Giving it more gas usually smooth's it out. It will run on up to
> redline and shift into the next gear and has no problem running up to
> 90 mph.

There's your problem--you are going faster than what the speedometer goes up
to.




From: Jim Warman on
Vacuum leaks when cold a fairly common with most flavours of the 4.0
Explorer engine that feature the plastic upper manifold... Easiest way to
check for the concern is to smoke test the intake after a cold soak... this
type of concern generally doesn't have a coolant leak to accompany it.

The upper intake is sealed to the lower intake with six individual "o-rings"
.... any or all of these can leak.


From: Ashton Crusher on
I have not noticed any increase in oil usage. Plugs 2 and 5 are
exceptionally clean and white. The others are more of the normal
"gray". What's the scoop?

On Sun, 21 Mar 2010 05:50:43 GMT, "Jim Warman"
<mechanic(a)telusplanet.net> wrote:

>Codes? Is it using more oil than normal? Check plugs #2 and #5
>
>
>"Ashton Crusher" <demi(a)moore.net> wrote in message
>news:f139q5pqoneubqpu8066a75eamlufajvm3(a)4ax.com...
>> 92 Ford Explorer 4.0L OHV V6 130K miles, 10K on double plat plugs,
>> nearly new plug wires. O2 sensor was replaced about 40K ago
>>
>> Sometimes Runs rough when first started. Not just first start of the
>> day, but even when warmed up and then shut down for 15 minutes it will
>> often run rough initially like one cylinder is missing.
>>
>> Roughness usually goes away after it's warmed up but lately it's
>> started to have a bucking/missing/popping under light acceleration.
>> Giving it more gas usually smooth's it out. It will run on up to
>> redline and shift into the next gear and has no problem running up to
>> 90 mph. So unlike what I think of as the typical 'worn out plug"
>> misfire that shows up at high rpm and high load, this show up at
>> medium rpm light to medium load.
>>
>> It has not turned on the check engine light
>>
>> Any ideas?
>>
>> Things I'm thinking it might be..
>>
>> water in gas
>> bad gas
>> bad injector(s)
>> bad coil
>
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