Engine
Intake Removal to Repair "Flappy" Valve
Dave Chamberland's thrilling, lavishly illustrated article on how to remove, spiff up, and replace
the air intake manifold (including the famous "flappy") on '87+ cars is now up and available for
download on the 928 OC's members-only Web site (go to the 928 Journal main page).
Leonard Laub
Editor, 928 Journal (928journal@928oc.org)
Hi all.........WOOOOOOOOOOH, that's my first words after going in deep for the "FLAPPY". I
had my intake gaskets and was ready for battle......so I started going in deep to re-attach the
vacuum line to the actuator that controls the flappy. All was going well, all the plastic comes
off....then the fuel line bolts....they were a little stuck but came along with some gas to boot....I
left the injectors in place and lifted the whole rail, not a problem..in both sides, three injectors
came out and one stuck behind and was just pulled out with little force and re-installed on the
fuel rail. Had to do some creative thinking in getting the airbox supports out of the way and
then onto the intake bolts....they all came off with little problem. Now is where it gets crazy!!
This is the part where you wonder why you did not take it to the dealer......there are so many
lines under the intake it is mind boggling. We disconnected the easy - obvious ones and then
opted to unbolt the 4 bolts holding on the bottom part of the intake that has the air mass sensor
attached as well as allot of other lines....just did not need to get into that "Pandora's Box". We
had the front end of the manifold propped up and could see the "Holy Grail"....the flappy
actuator....man, they could not choose a more difficult spot to put it. We hooked up the
vacuum line and then tried to actuate it by sucking on it....nothing, and we were wondering if
the diaphragm in the actuator was toast. My friend works in a lab and we were off to test it on
the vacuum machine. It worked fine and held a strong seal.....so that is one less part off the list.
Upon opening up everything we found one of the return lines by the oil filler was decayed and
torn apart...swollen with oil. So I'm off to get that hose in the morning...part # 928 107 445 02
(funny how the part number looks perfect and the rest is torn up). Also, I recommend anyone
going in to replace there oil filler gasket.....mine is leaking and the V had enough oil in it and the
oil sweats onto the hoses and the like. Also, the intake has some residue in the first part of
every intake tube....going to clean that up. My intake can use a beadblast and re-paint but that
will have to wait...I need my daily driver back. Right now the intake is in the garage and I have
to pick up the gasket and hose tomorrow and then we can put her back together after some
cleaning......hopefully everything will run well and better than before....I labeled most of the lines
and should be alright....but these cars don't let you have anything easy :^) Oh by the way...my
car has 90,000 miles on it and the original intake gaskets were in fine shape, but I bought new
ones just to make sure.
Will fill you in on the rest when the job is done and MY FLAPPY IS FLAPPING.........HERE
COMES 30 HP!!!
Take care, Dan 87 black/black, 5 speed
Hi all.........just got back from the dealer and my friendly Porsche mechanic. I showed him the
vacuum unit that actuates the flappy (it is in the heart of the intake).....this is the one I thought
was bad, then tested on a lab vacuum system and thought was good......now it is proven to be
bad. The P-mechanic hooked it up to a mini-vac and it showed not holding much if any of a
vacuum. He said that the diaphragm in the unit sometimes gets a hole in it and will hold some
vacuum at one point but not others....so it is bad and I do not want to go this deep to replace it
again so a new one is ordered along with a PCV hose and the little cap that goes on the top of
the intake to cover the top piece of the flappy.....and of course the oil filler gasket, which is
probably the cause of a lot of hose rot due to the oil that seeps into the area. Our cars run HOT
in the engine bay and toast a lot of rubber and gaskets.....so every chance you get - inspect and
replace. All the other hoses are good, just the one closest to the oil filler gasket is rotten and
cracked in two places. So, the parts will be here in 2 days and I will spend those cleaning up the
interior V and areas, as well as the intake.............by the week-end I hope to have the shark at full
strength........will tune in then.
Take care, Dan 87 black/black, 5 speed
Hi all........sorry about the day delay, but ran into some problems buttoning up the shark after
her flappy vacuum unit went in. I got all the new hose, vacuum unit, and o-ring for the oil filler
all installed and was closing up. I read in my spec book that the intake manifold gets spec'd to
15 Newton Meters, I saw a web site that had a converter on it and I plugged in 15 Newton
Meters and it gave me 3.65 or close to that of Foot pounds of pressure......so I did it that way.
Closed it all up and went to start the car and realized I had no pedal tension! It had sunk all the
way to the floor......went to the throttle assembly....nothing, all loose. I turned my car over, it
roared to life and then sputtered like it was going to die and a huge sucking noise was coming
from the engine. Turn it off and call it a night. Today, after a poor nights sleep....I get up early
and go to the Porsche dealer to ask the mechanic a question or two about my two symptoms;
poor idle and no throttle. He said there is a plastic pulley behind the air box that the throttle
cable from the intake loops around and goes to the pedal. He said it probably got some slack
when I was working on it and came undone.....He was right.
The second symptom, the gushing air......was guessed to be the intake gasket...and after all the
numbers research and calling we found out to torque to 11 foot pounds and did so and closed
her up. Started up and bobbled around until it corrected itself....... THE FLAPPY IS AT FULL
GO NOW. The top piece cycles at a 1/4 turn upon start up and goes for the 1/2 turn at about
4,000 rpm.....so that was a success. My only problem was the car made a slight sucking noise
and was idling at 1,000 rpm instead of its usual 700 or so. Feeling frustrated and beaten....I
went back to the P-mechanic for a question or two and to check the price of the insulating foam
that was toast under the fuel rail cover.....$ 47 Canadian PER SIDE !!.....I think I will find some
insulating foam else where. Anyway....the mechanic said only "you are sucking air and have a
vacuum leak somewhere".....so I'm thinking of all the hoses I touched and dreading waking up
tomorrow and repeating the removal of the intake for the third time. So I call David Roberts for
an expert opinion.....He said you are sucking air and to check the 5-way double T vacuum
connector under the air box by the fuel rail end on the drivers side. Let me say that David is the
man......he called it. I went looking, it took awhile because it is packed behind some line and
your view is obstructed, but I eventually found the short ( 2 -3 inch) vacuum line coming off
the ball like fuel pressure regulator ( I think ) that is a couple of inches off the end of the fuel rail.
We were manipulating that ball piece to get the last manifold bolt hole off.....I guess we pulled
it off. It was a hard bugger to get back on....still not on like I would like (will work on that). I
started her up and without the airbox on and she idles at 700 or so......so I think that was it......I'm
going for a test drive now and check out everything....Especially the "Flappy Feel" . Will tune
in later..
Another public thanks to David Roberts for knowing these cars so well and saving me from
taking off the intake again to solve nothing...and maybe create another problem....THANKS.
Take care, Dan 87 black/black , 5 speed w/RMB and FULL FLAPPY
[Later that same night:]
Hi all, me again.........just an add on to all the problem solvers out there....I still have a vacuum
leak even though I re-connected a vacuum line behind the airbox. More clues.......I drove the car
a fee hundred feet with the airbox off and the car idled at a 800 instead of 1000....also when the
car is shut off there still is that raspy air gurgle for a second after......then as I gather my things
there is a strong smell of gas.
I'm probably going back in deep tomorrow or Saturday......we suspect a vacuum line that
attaches to male connector on the bottom of the intake as there is not much slack with that line
and if you lift the intake up too high it will disconnect.
Take care, Dan 87 black/black , 5 speed w/RMB
Hi all, the latest is the car runs fine...lots of power and smooth, It just idles at 1000 rpm instead
of the 675 +/-25. I have been calling DR left and right to ask questions (THANKS)....found an
unconnected fuel regulator line that was probably knocked of during the intake
removal.....connected that but still the 1000 rpm idle. It was then suggested to spray water
around the seals of the intake and the throttle body meet the intake, which I
disconnected......later heard that you should try not to break that seal, but it seemed better than
disconnecting all the wires, hoses, and lines that attach to the throttle body......the factory seal
was a gasket and the use of silicone.....so I guess they wanted to make sure it sealed. I sprayed
water around the area but did not notice a decrease in idle or any water reaction. I then did this
later with a friend and the car definitely dropped idle and it looked like the water on the ledge of
bottom throttle body where it meets the intake manifold was getting sucked in (DR's guess
again...he is 2 for 2 so far on this) then the idle would drop.....so all things point to that seal, the
only question might be the vacuum line that attaches to the bottom of the throttle body...there
is little slack and if we pulled it off moving the intake around then it would be lying on the floor
of the V sucking air...or water if I sprayed enough around that it collected there. Because I only
noticed the drop in idle the second time, that might be a possibility.....but then there is the
inward movement of the water (or so it appeared). Anyway....I ordered the 2 gaskets for the
throttle body-intake seal ...they are a couple of bucks each...any will keep trying to add clues as
to what is the real problem.....then go in in a few days and secure the line and change the
gaskets and silicone them....close her up and check all the vacuum line and hope that did the
trick.
Will tune in with the results.........BUT HEY MY FLAPPY WORKS GREAT !!
Take care, Dan 87 black/black , 5 speed w/RMB
Hi all, Dan up here in Winnipeg, Canada. I am finally done my flappy fix / vacuum leak, project.
I replaced my vacuum unit for the flappy a month ago and had that working fine only to
discover a high idle (1,000 rpm instead of 675 rpm). So I had a vacuum leak. Well called
everybody (thanks for the help) and narrowed it down to the throttle body gaskets. When I
opened up the intake the first time I replaced the intake gaskets but not the throttle body ones
(and I did separate the throttle body from the bottom of the intake). I went with the old gaskets
and some silicone and was left with a vacuum leak. So I got new gaskets ($10 Canadian for 2)
and was ready to do the job....but went on holiday for 3 weeks so now I'm back and got to it. I
was not sure if I should put the new gaskets in as they came or add a sealant. After some
calling around.........Porsche said not to put anything on the gasket as it came with a bead of
sealant on one side already.....the P-mechanic at the local dealer said the same......some other
suggested a sealant. I went with nothing. Just cleaned the surfaces smooth and then bolted it
back together. Looking back, it was probably good not to add sealant as we had a tough time
lining up the bolts and keeping the two surfaces together....the throttle body was still attached
and in the V of the engine and that made it tough to get at the bolts comfortably. We got it all
together with just a little stress and then noticed there was a hose not attached to the throttle
body!! We did not know if we just knocked it loose or that is was off from the last time we were
in there. It is a hose the size of a PVC hose on the side of the intake....2 hoses come to meet one
and then it attaches to the throttle body. We pushed it back on and made sure everything was
correct, then buttoned it up. Started her up and she ran fine right away......idle at 675. Took her
for a run on the highway and she flying now with her new flappy and no vacuum leaks. Good
thing, tomorrow is going to be my second track experience..... looking to improve on last
month's time now that the FLAPPY IS BACK. Special thanks out to all that helped out during
this whole lengthened fix......literally, could not have done it without you.
Take care, Dan black/black, 5 speed w/RMB & FULL FLAP