after cracked manifold replaced, high (redline) rpm on startup

I replaced my cracked exhaust manifold on my 99 Jeep Wrangler 4.0L
(I-6). Note that this is really probably the 2nd time I try such a
large job (at least I usually just deal with oil changes). This
required the removal of the intake manifold also (because both intake
and exhaust share the same gasket). I made sure I removed everything
carefully. I disconnected 2 electrical connections and about 6 or so
hoses, and of course the fuel line.

I re-tightent the bolts according to the sequence suggested (center
bolts first and then the outer). I tried to turn the jeep on, and the
engine just rev'ed really fast to redline. I immediately turned it off
(the first time probably let it run for 5 seconds). I double and
tripled checked the vacuum houses and all the connections I touched
during the replacement of the exahust manifold. Note that I did not
replace any hoses, except for a connector from the air intake that I
broke while trying to remove it. I still need to check to make sure I
torqued all the bolts to the correct amount. I tried turning it on
about 6-8 more times to see if It would eventually come to a normal
idle, but it never did. I actually did not let it run more than 1-2
seconds since every time I turned it on, it revs so fast, almost as if
I were pressing on the accelator. I did checked the throttle, and its
not stuck.

My question is if a leak in the gasket or a vacuum hose will cause
this problem? Or what other things could I have screwed up while
replacing the exhuast manifold? Any suggestions I can try would be
very helpful.

-Juan

 

Sounds as though you have a throttle connection binding or improperly
connected. My guess is the throttle is stuck full tilt.
Scott

 

Left off the return spring?

Earle

 

Loosen the manifold bolts and wiggle the intake around until they seat.
God Bless America, Bill 0|||||||0
mailto: http://www.billhughes.com/

 

Or what other things could I have screwed up while

Somehow, you didn't put the throttle back together correctly. Your
throttle *has* to be wide open to rev the engine like that. A closed
throttle would not rev the engine, no matter what else you did.

 

I should have taken L.W's advice about loosening and wiggling the
intake. Instead I decided to start checking each screw by tightening
each one to make sure it was at the correct setting. Well, it turns
out that the intake was not seated properly. There are 2 holes on each
side of the intake that are suppose to line up with engine. One of
them was not lined up and as I tighted the screw (since it was not
torqued to the correct amount) it broke of a small pieace of the
intake. In any case that meant that whole side was loose. So I began
to tighten each bolt again, and when over them several times. Turned
on the Jeep, and it was back to its normal idle speed . I can live
with the small chip on the intake, as it appears to be running ok. I
plan on driving it on short drives, and re-check the bolts in a couple
of days. Thanks for everyones suggestions.

 

Thanks for telling us what your solution was. We live and learn, by
trial and error.
God Bless America, Bill 0||||||
mailto: http://www.billhughes.com/

 

Thanks for the update. It is a bit common to have issues with that long
intake.

Just FYI, the torquing should 'start' in the center and spiral out to
the outside bolts, not alternate inside to outside. This will make it
stay put better.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
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Well, it turns out that the intake was not seated properly.

Effectively bypassing the throttle and making it a non-throttle.

 

In your worry about subtle things, never overlook the obvious. Did you
re-connect the throttle return spring and throttle cable correctly?

 

bet you did not get inatke manifiold seated on head correctly and now have
a vac. leak there

 

Thank for the follow up Juan.

Merrill