Intake Removal to Repair "Flappy" Valve

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

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