I just replaced the lower intake manifold gaskets and upper plenum in
my '98 Olds Intrigue (with help from the people in here).
Car now ran good and has good power, but after driving a short time,
I noticed the car has a vibration, at idle only, it kind of lopes, and
I opened the hood and could see the engine visibly rocking.
I recall when I was re-assembling the engine, and upon opening the
Dorman UIM set, I noticed two different sets of o-rings, 6 apiece.
One set looked like every other GM injector o-rings I've ever seen...
while the other six looked slightly larger diameter, and thinner.
Since the injectors are a smaller diameter on top than bottom, I used
the larger diameter but thinner ones for the bottom of the injectors.
They didn't seem to fit that tight, but I found the other ones to be
such a tight fit I could not really get them on, without being afraid I
was going to break the injector tip while putting on the o-ring.
Besides, what would the other set of 6 been for?
When finishing up and plugging the wiring harness onto the injectors,
I noticed the injectors would rotate in their bores quite easily, even
though the rail and everything was torqued down. I thought that was
kind of strange, and I remembered that the o-ring issue didn't set quite
right with me, but continued on.
Anyway, the car runs as described as above. No MIL, and I put my
vacuum gauge on the fitting that goes to the power brake booster, and
drove it around with the gauge taped to the windshield, and the needle
behaves exactly as it should at various loads, etc, it reads right in
the green, and steady at idle. I did this to see if it would point to a
possible vacuum issue causing the rocking at idle, but it was
Also, and this probably is unrelated, but I notice the cooling system
doesn't have the pressure I would expect at operating temperature, the
upper hose isn't very hard.
It doesn't drink or leak any coolant. I have not yet checked the
radiator cap, although I would have presumed the cap held good pressure
since this whole situation began with the engine hydro-locking as it sat
overnight -- so presumably the cap would likely have been holding at
pressure when the gasket failed and flooded the LIM with coolant. But
maybe not, I guess.
My questions are:
1). Since many of you have likely replaced the UIM with the Dorman
unit, I presume you know of the second, larger set of 6 o-rings included
in the kit... if they aren't for the larger, bottom part of the
injector, what are they for?
2). If the fatter o-rings do indeed go onto the bottom of the injector,
is there a special tool for installing them, or are they just
surprisingly difficult to install and you really have to wrestle them
onto the injector? I don't know what the bottom of the injector is made
of, but I was under the impression it was breakable if you put a lot of
pressure on it.
Any advice appreciated, TIA. I love this forum and you guys are very
knowledgeable and helpful