David '96 993

Steve,
Thank you once again for your terrific contributions to Rennlist. To confirm what Steve has said, most shops that I have spoken with that have pulled the heads have said that it was a valve guide issue. I am watching my oil consumption carefully and find that I go through a quart every 2200-2500 miles. It seems to vary slightly when I am doing more track events.

I think that my carbon issue may be a bit unique and that when I do start burning more oil. I don't want to do this any time soon.

Richard C2S

Our 993s are getting older and farther out of warranty every day. Is Porsche still doing valve jobs as a warranty job if the car suffers from the dreaded carbon buildup?

Pete in DC

Steve96: I'm in Chevy Chase and have the Auterra/Pam setup if you want to buzz by, run the scan, see the codes and reset. Not a permanent solution, but it took me about 3 mins. to confirm the air passage issue and reset for now.

Lorenfb

Sounds like most 993 owners are finally getting and accepting the
real source of the secondary air injection problem. For some, it does
take awhile.

So, lighten-up on those continued high revs (mistakely to eliminate
carbon) and you guys might avoid valve jobs in the near future.

Have Fun
Loren
'88 3.2

Steve 96C4S

Pete in DC - I'm there! Can you email me privately: stever500@comcast.net and let me know when you're available? I'm available during the day, as I'm in sales with a VERY flexible schedule. Or if it's after hours, I could work that in too. I just hate driving the car with that idiot light (CEL) on. It's staring me in the face again now with it's gruesome orange glow. Perfect for halloween.

The worst thing is when you pick up a buddy and they lean over and say: "Hey, uh, you know that check engine light is on again... is that serious? Jeez - that thing comes on alot, doesn't it? Wasn't that thing on the LAST time you picked me up? Don't you ever bring it in and get it fixed after seeing a warning like that? Man, that darn light would make me REAL nervous..."

Aaaargghhhhhhh!


Steve

Steve Weiner-Rennsport Systems

Hi Loren:

From what I've seen by looking at various 911 heads over the past 20+ years with this, high-revs will not increase-decrease the likihood of needing valve guide replacement or not. In fact, it makes little difference to oil consumption, as well.

Its all about a QC issue during manufacture combined with less-than-optimal choice of materials.

I'll also tell you that cars that are idled a lot and driven gently exhibit FAR more carbon (of both kinds) in the intake tract, piston crowns, and exhaust ports than ones that are driven spiritedly,.....

phatbut

Thanks Steve and everyone who has given their feedbacks and opinions on this issue.

Steve..when are you gonna open a shop in Sunny Southern California? Until you do...do you/or anyone in Cali, greater Los Angeles area, recommend a particular shop?

Randy M

From what I've heard and from speaking with him when I was looking for a C4S, Tony Callas at Rennsport in Torrance is a solid choice. All you so cal guys could chime in....
P.S. I'm buying a house in Sherwood, OR. that is extremely close to Steve's shop (5 mi + -) I'm not sure if thats such a good thing...

911

phatbut,

Check your PMs.

Rich

RMEllis

My car now has 48,000 miles on it and the "light" first came on about a year and a half ago. I brought it to the shop and they told me that it was carbon build up in the ports and it would cost about $1k to fix. I read all of the posts here put in some techron and drove it in a spirited manner hoping to burn out the carbon. Six months later the light came on again so I had it reset again and once more spirited driving. To make a long story short it came on a month ago, had it reset and then it came on again on Tuesday so I bit the bullet. My mechanic charged me for 11 hours to pull the exhaust off, put some chemicals in and use some wire to clean the ports. Total damage $988.24. He said the ports on the left side were close to plugged solid and on the right side almost solid in the front and almost clean in the back. No mention was ever made about valve guides. I believe that the people who owned my car before me drove it quite conservatively and when I got it two years ago the problem was well on it's way. Now I will continue to drive spiritedly and hope the problem does not reappear. I wish I did not love my car so much that I could tape over the check engine light but I just can't.

User 4621

Just to clarify what appears to be a common misconception about the whole "spirited driving" thing.

I have not seen or heard any evidence that it would fix an existing problem. Rather, 993's that are driven as intended are less likely to develop various problems in the first place.

The clogged air port issue appears to happen almost at random based on a manufacturing issue and there is probably no way to avoid that specific issue by driving one way or another.

Spirited driving does not mean "constant high rpm" driving. It means allowing the engine to operate in the sweet spot of it's rev range, typically 3k+ rpms, with an occasional burst up to redline.

I think that the reason this comes up a lot is because many 993 owners come from luxury car backgrounds and tend to drive around at 1500-2500 rpm's, which is fine in your Lexus but I believe is NOT healthy for this engine. I think this is the point that Steve was making.

Constant near-redline operation is a racing condition and will wear out your engine quickly in street mileage terms.

phatbut

Rich...Thanks for the PM, but no thanks. I have not set up an email account with Rennlist yet. Can you please forward your PM to asprer@aol.com

Randy...thanks for the info

Steve Weiner-Rennsport Systems

Oh-oh,.......Perhaps I should make a reservation,....

Chris Cervelli

I own a Porsche shop in Arizona. I have yet to see even one 993 have this problem. I wonder if the incredible heat here has some effect on this?

I see worn out valve guides on 99% of post 1990 911's that come thru the shop but no CEL for SAI issues. The increased engine temps here must prevent the oil from stocking in the passages.

One thing that is for sure: Steve is dead on when he says that easily driven cars have more carbon problems. I also support using non-Porsche valve guides when repairing cylinder heads.

Lorenfb

Common sense and facts would have to differ with your
conclusions, Steve!

Facts;

1. Porsche has the resources to select and use any
materials they wish given what they sell Porsches
for. Twenty-four guides at $100 a piece (If they
wanted.) makes little difference in the price of $60K
car. Porsche pricing at their levels is basically
inelastic. The guide material used was optimized for
all engine conditions/parameters.

2. The statement that it's a Q.C. problem is ridiculous.
Porsche out-sources most all their parts and can
force vendors to tighten their quality.

3. Friction causes metals to wear.

4. A non-running engine has zero valve movement in the guide
with no friction generated and thus ZERO valve guide wear.

5. An engine reving a 2000 rpms has one third the valve travel
as an engine at 6000 rpms and thus one third the resulting
overall friction & wear.

As stated, it's the oil from the valve guide wear causing the
carbon buildup. Internal parts experience friction as they move
and thereby wear. Yes, there are other factors, but friction is
main contributor to wear.

Common Sense:

Why does a 200K mileage engine sell for less than a 50K one?
It's the wear. Wear (total friction) is correlated with mileage.
Why do race engines only last one or two races before they get rebuilt?
Could it be that they run at or near max rpm and wear to the max?

Let's asume it's a materials problem. No matter what material
is used, there still will be friction. The max wear point will change
(different mileage), but it'll still exist and oil burning will eventually
become problematic.

Use a little common sense or "race on" to the next valve job.

Oh Steve, did you say that you do a lot of valve jobs?
Is what you tell your customers, what you've posted?

Have Fun Guys
Loren
'88 3.2