1984 Porsche 928s possible vacuum leak - HELP? :)
03-19-2014, 03:42 PM
#1
Track Day
Thread Starter
1984 Porsche 928s possible vacuum leak - HELP? :)
Hi guys,
A few weeks ago I posted about a possible issue with the fuel delivery system on my 1984 porsche 928s L Jetronic US edition.
I *think* by getting the injectors cleaned and replacing the fuel regulators, and fuel dampener, it fixed the issue slightly. The car still only starts when it's in the mood, and I'd say it runs a maximum of 10 minutes. When the car is running I can hear a lot of air leaking out of somewhere. (I'll try to post a video to youtube so you can hear).
Long story short I think it's a vacuum leak, but I need to know if this hole (pictured) is normal, or should it be sealed up?? Yes I removed the spider to check for leaks, so it will be put back on before any testing.
A few weeks ago I posted about a possible issue with the fuel delivery system on my 1984 porsche 928s L Jetronic US edition.
I *think* by getting the injectors cleaned and replacing the fuel regulators, and fuel dampener, it fixed the issue slightly. The car still only starts when it's in the mood, and I'd say it runs a maximum of 10 minutes. When the car is running I can hear a lot of air leaking out of somewhere. (I'll try to post a video to youtube so you can hear).
Long story short I think it's a vacuum leak, but I need to know if this hole (pictured) is normal, or should it be sealed up?? Yes I removed the spider to check for leaks, so it will be put back on before any testing.
03-20-2014, 08:41 AM
#2
Rennlist Member
Bryce,
I don't think so. But I don't have an Ljet car here to look at right now. Hopefully somebody else does and will post!
Here are some old shots that might give you clues, might not. Best I can find right now.
I don't think so. But I don't have an Ljet car here to look at right now. Hopefully somebody else does and will post!
Here are some old shots that might give you clues, might not. Best I can find right now.
03-20-2014, 11:05 AM
#3
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I'll try to get into the garage this weekend and get a look at my throttle body. I would hazard a guess that the inlet you are asking about should either be blocked or connected to something.
03-20-2014, 11:52 AM
#4
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Just tried sticking an Allen wrench in that hole on my 84 US 5 speed and it is blocked inside the hole....broke my distributor vacuum line in the process....I guess that means it needed to be replaced anyways....lol
03-20-2014, 11:55 AM
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There is an earlier post by me which was after I snapped multiple vacuum lines changing my plug wires. I found it easiest to trace everything starting at the fuel pressure regulators based on the under hood diagram.
03-20-2014, 04:04 PM
#6
Track Day
Thread Starter
Thanks for the replies, guys.
I haven't had a whole lot of time to look at it, but I felt around in that hole, and it appears to be blocked from the inside just as Hayden said(sorry about your line). Is it possible that maybe the car is dying because the MAF is not sealing well around the throttle body? (I noticed that it was kind of loose but didn't think anything of it until I took the spider off and it fell out of its spot entirely).
On a brighter note I am getting the engine cleaned while I have it "opened up" (car sat for 5 years before I purchased it, yes I flushed all the fluids and when it does start up it runs great)
I haven't had a whole lot of time to look at it, but I felt around in that hole, and it appears to be blocked from the inside just as Hayden said(sorry about your line). Is it possible that maybe the car is dying because the MAF is not sealing well around the throttle body? (I noticed that it was kind of loose but didn't think anything of it until I took the spider off and it fell out of its spot entirely).
On a brighter note I am getting the engine cleaned while I have it "opened up" (car sat for 5 years before I purchased it, yes I flushed all the fluids and when it does start up it runs great)
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03-21-2014, 08:47 AM
#8
Rennlist Member
If the throttle body is moving around the rubber buffer mounts it is secured to the block by are probably broken. 928-110-191-00
Readily available but a real PITA to remove .
Readily available but a real PITA to remove .
03-21-2014, 09:49 PM
#9
Nordschleife Master
Bryce,
Your car does not have or use a MAF. It has a AFM also known as a barn door.
Might I inquire as to the green wire? Has it been replaced recently?
Your car does not have or use a MAF. It has a AFM also known as a barn door.
Might I inquire as to the green wire? Has it been replaced recently?
03-21-2014, 10:03 PM
#10
Rennlist Member
Bryce,
Assuming when you say a loose MAF that is the AFM , there is a large O-ring in the throttle body where the AFM sits. It is a tight fit. I usually lube mine with wd-40 to insert the AFM. That said, the O-ring costs about $10. I may be wrong but it looks a little funny in one of your pictures.
Good luck,
Dave
Assuming when you say a loose MAF that is the AFM , there is a large O-ring in the throttle body where the AFM sits. It is a tight fit. I usually lube mine with wd-40 to insert the AFM. That said, the O-ring costs about $10. I may be wrong but it looks a little funny in one of your pictures.
Good luck,
Dave
03-22-2014, 04:51 AM
#11
Rennlist Member
That big O-ring gets flattened and is one of the important items to replace on a 16 valve intake refresh. A new one is tight enough to hold the afm proud; old one can really leak bypass air. Use a smear of dielectric grease to seat new one. For temp use, waiting for parts, I've wrapped afm with duct tape to cut the leakage. Won't last long but let's you keep working with car.
IIRC, like on 32v, 3 little motor mount looking things are what mount 16 V throttle body to valley. A pair of bigger ones mount air cleaner housing to engine. Their relative locations are important and are usually pretty skewed when old. As you also know, afm mounts to bottom of air cleaner housing. At this age, unless very lightly used, all 5 mounts have hardened in deformed shape. Replace all mounts and O-ring, and afm will align with the receiving hole in throttle body again perfectly. Yes it can leak a whole lot of air prior to those refreshes. Not to mention it's a PITA to work on the car when all that stuff is misaligned.
IIRC, like on 32v, 3 little motor mount looking things are what mount 16 V throttle body to valley. A pair of bigger ones mount air cleaner housing to engine. Their relative locations are important and are usually pretty skewed when old. As you also know, afm mounts to bottom of air cleaner housing. At this age, unless very lightly used, all 5 mounts have hardened in deformed shape. Replace all mounts and O-ring, and afm will align with the receiving hole in throttle body again perfectly. Yes it can leak a whole lot of air prior to those refreshes. Not to mention it's a PITA to work on the car when all that stuff is misaligned.
Last edited by Landseer; 03-22-2014 at 05:12 AM.
03-25-2014, 06:15 PM
#12
Track Day
Thread Starter
Neilh: They are indeed broken. Would JB weld be appropriate for sealing it back on? Or should I take the time to replace them with new ones?
Lizard 928: The green wire has not been replaced recently, although it doesn't appear to be in bad shape at the plugin.
j.kenzie@sbcglobal.net: I will order a new O-ring. I think this one is the original, and the car sat outside for about 5 years before I bought it. D:
Landseer: Yup I'm thinking replacing it is a good idea at this point.
--------
Now a little bit of an UPDATE! I checked every vacuum line on the car, pulled everything off the top of the block/heads. At this point I think I actually found the problem. Something I neglected to check were the SPARK plugs! They are charred black. I'm thinking at this point the car is running super rich, which would make sense. It will run fine without the fuel pump relay plugged in, but once it's plugged in, it sounds like the engine floods itself and dies. Very possibly the AFM or O2 sensor. I will investigate this further.
Here are some pics!
ME!
Cleaning the engine a little.
She needs some excessive loving.
Lizard 928: The green wire has not been replaced recently, although it doesn't appear to be in bad shape at the plugin.
j.kenzie@sbcglobal.net: I will order a new O-ring. I think this one is the original, and the car sat outside for about 5 years before I bought it. D:
Landseer: Yup I'm thinking replacing it is a good idea at this point.
--------
Now a little bit of an UPDATE! I checked every vacuum line on the car, pulled everything off the top of the block/heads. At this point I think I actually found the problem. Something I neglected to check were the SPARK plugs! They are charred black. I'm thinking at this point the car is running super rich, which would make sense. It will run fine without the fuel pump relay plugged in, but once it's plugged in, it sounds like the engine floods itself and dies. Very possibly the AFM or O2 sensor. I will investigate this further.
Here are some pics!
ME!
Cleaning the engine a little.
She needs some excessive loving.
03-25-2014, 06:19 PM
#13
Rennlist Member
>>
Neilh: They are indeed broken. Would JB weld be appropriate for sealing it back on? Or should I take the time to replace them with new ones?
<<
I have used super-glue on them in the past as a test, - doesn't hold, replace them.
Nice looking project, BTW.....
Neilh: They are indeed broken. Would JB weld be appropriate for sealing it back on? Or should I take the time to replace them with new ones?
<<
I have used super-glue on them in the past as a test, - doesn't hold, replace them.
Nice looking project, BTW.....
03-25-2014, 06:34 PM
#14
Rennlist Member
Yep stay at it, it will all come together 
I would suggest resealing the Oil Filler to the block (two #10mm bolts), easy to do at this point. You can make a gasket and use some good silicon sealant of your choice one that's used for sealing Oil.
Dave
I would suggest resealing the Oil Filler to the block (two #10mm bolts), easy to do at this point. You can make a gasket and use some good silicon sealant of your choice one that's used for sealing Oil.
Dave
