Question about 1990 Porsche 928

2 Answers

My 928 GT

When I initially got my 928 GT, I got it at a great price, assessed value from an appraiser was nearly double what I paid for it!

now, there are the obvious electrical gremlins, but the body is in great shape, and for the most part it runs exceptionally well.

Now, here are my two problems, for the most part, the engine has run great, but sometimes runs a little rough, and after running it through a high pressure wash, it stalled out, couldn't figure out why at first, ultimately determined water got in through the intake, popped off the air filter, which I discovered had a sizeable crack in the seal (had already made plans to get it up to a Porsche mechanic in Calgary to fix the few things wrong with it), found that debris had gotten through the crack, and was sitting on the screen, I removed the debris (and later put silicon sealant on the crack to reduce the problem until I can find an air filter for the car), assuming smaller debris had gotten through the screen....started the car with the air filter off....after a few tries it quickly roared to life...problem solved, however with the debris, I suspect the engine has gotten some **** in it, as it hasn't been running perfectly....will an engine shampoo solve the problem? or am I looking at some costly repairs?

Now, the other thing (and I suspect it's connected to the diff. issue), when I got the car, PSD light was on, meaning the PSD had been disengaged due to some problem.....that was one of the things I'd planned on getting fixed in, one thing I absolutely LOVE about my 928, is that while it might not corner quite as well as some other cars I've owned or driven, it's an AMAZING drift car....NEVER experienced a car that was so easy or precise to control while sliding sideways at high speeds.....anyway, one day when I took a female friend of mine for a drive, I drifted a few corners, and found that around the 4000-5000 rpm mark there was significantly less power than normal, and a great deal of vibration in the shifter accompanied by a bone chilling rattle that sounded like gears grinding behind me....also, tires weren't spinning like usual, not entirely clear on the drivetrain setup of the car, but from what I understand of it, this is a good sign the differential is this the case? will the Diff (which I understand is amazingly durable in this car) need to be replaced? or will a simple rebuild do?

plz....I need to know what kind of expenses I'm looking at I can budget....(I do have approximately $4000 to put into the car, but there are other things I'd like to get done as well.)

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  • jhudes Oct 15, 2008

    Engine shampoo is what I've heard it referred to when they pop off the valve cover, and give the internals of the engine a good cleaning.....typically costs about $150-300, and in my experience, makes the engine run a lot better.

    The PSD light is the warning light for the PSD (as I'm sure you know, Porsche's version of an electronically controlled Limited Slip Differential).

  • jhudes Oct 15, 2008

    Engine shampoo is what I've heard it referred to when they take off the valve cover and give the internals of the engine a good cleaning.....generally costs $150-$300 and in my experience, makes the engine run alot better (witnessed in an EF Civic Si used for rally racing....dialed in a 4 hp increase, and better fuel economy and crisper, smoother engine idle, and crisper sound at higher revs).

    The PSD light is the warning light for the PSD (as I'm sure you know, Porsche's version of a Limited Slip Differential).

  • jhudes Nov 01, 2008

    thanks, lol, I'm not too concerned about cost, I intend to keep it as a show car rather than a daily driver (it's a great drift car btw), so maintenance will not be so bad. I was well aware of the electrical gremlins, but after finding one in such decent condition, at the price, I had to get it. I've already had offers double whatI paid for it from some true car enthusiasts, so worst comes to worse, I can always sell it (though I'll have to do it at the right time).

    The crack was in the air filter, not the intake.

    Yeah, it's going to Two-Square in Calgary in the next week or so...the mechanic I've been speaking to has owned several 928's and seems quite passionate about them.

    Thanks for your input. Out of curiosity, would it be a feasible modification to move the fuse box/relay panel to a better protected location?

  • yadayada
    yadayada May 11, 2010

    What is engine shampoo? What is a PSD light? To much info, short sweet and to the point, thanks



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I just bought a 1990 928s4 and it also has the PSD light on, meaning the PSD had been disengaged due to some problem....
I was wondering what jhudes on Oct 15, 2008, found out about the problem, and what work was done to fix it, and the ultimate cost
Please respond!

Posted on May 06, 2010

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Let me give you my heart felt feelings of sadness for you. I love the 928's. They are positively one fo the best touring / GT cars ever produced. But they have a huge failing, the electrical system. I worked for Porsche for 15 years and I have seen some wild S**T in those electrical systems. Why Porsche decided to put the fuse / relay panel right below a huge hole in the cowl that will, someday leak, is beyond me. The 928 is the most expensive Porsche to own now. You know just try to find parts and when you do they are gold. As a mechanic I had to finally sell my 928 GT S4 because I could not keep it. But I can keep my Lotus Esprit S4 and Hummer H1 because the 2 of them did not cost as much to keep.

Doing a 'top end' cleaning, if this is shampooing will always be a good thing. Also if there was a crack in the intake after the MAF sensor (thing with screen) the previous owner whould have to have the diaphram adjusted (little hole in the middle of the octipuss) to compensate. This takes a special, very long allen on a swivel end to adjust. Again this has to be done be a qualified mechanic.

Unfortunately without having my hands on the car I really have to say get it to a qualified person and leave it there. A true "friend of Porsche" will work with you and try to keep costs down by working on it in down time. There are a lot of prople that dont know the 928 find an old time Porsche guy that just loves the cars. Good luck.

Posted on Nov 01, 2008


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