CHEMICALMAN

I have a 96 C4S with a "CEL" on that I can not get rid of .It clears but comes on after 30-40 miles...--38K--(30k service done)
The car also has a rough idle.
I have changed the O2 sensors-(Twice),Knock sensor,air-Box vacuum line,Gas cap,and I did the Harness recall. The diag. code reads 5 separate Cylinder misfires. Any help would be greatly appreciated. I'm getting frustrated!!!!!--

(My 1986 Cab W/65k ran like a top!!!!!

Thanks in advance......Matt

96P993

The next thing you might want to consider is plugs, plug wires, dist cap and rotors....to start...

tom_993

Sounds like you’ve got the dreaded carbon build up problem. Do a search for that, it’s discussed quite regularly.

Tom
’95 993

rwilkoff

I'm new to this forum and am suffering with the mystical reoccurring CEL, (16 year member of PCA Potomac). My CEL just came on for the fourth time in the past 9 months, (96 993 C4 Cab with 44k).
1 - hairline crack in distributor cap - under $100
2 - Wiring harness replacement - Warranty
3 - O2 sensor replacement - $250
4 - Just happened - don't know yet, but dreading the carbon build up problem.
My car runs great with no evidence of degrading performance. It's been suggested that using BG44k additive, (every 4k), will help minimize or eliminate the carbon build up problem. Any thoughts or experience with this.

Thanks,
Bob

Jeff

I have exactly the same issue -- frustrating to say the least. I've replaced plugs wires and caps to no avail. I'm running an additive through now and am running the car at higher revs than I usually do (4500 vs 3000). I've sent you a private email in the hopes we can keep in touch -- one of us might get lucky. hang in there.

96P993

I was under the impression that the CEL for the carbon buildup came on more towards the beginning of start up then shut off after a couple of minutes. My check engine light has never come on within the first several minutes of running. I too was (knock on wood) getting the random multiple cylinder misfires. I never got the same cylinders, it was most definately random!!

Kevin Reilly

The most recent (August) Excellence features a 993 buyers guide with Jim Pasha reporting on one person's experience shopping for a 993. Out of the 4 or 5 cars that were looked at, two had CE light problems, and he said that one of them needed a $4,500 valve overhaul.
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> We soon found that the air-injection system was plugged with carbon, a typical sign that the valve guide seals have failed. The proper fix is a $4,500 valve overhaul. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">In the article's intro section, he writes </font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> One relatively common problem is leaking valve seals. The leaks trigger an emissions-related diagnostic fault which causes the Check Engine light to come on. This problem usually occurs in cars with over 60,000 miles that are regularly driven in traffic and thus subjected to higher-than-average engine compartment temperatures. The correct fix is to replace all of the valves and valve guides. This is expensive, about $4,500 in most shops, but a partial job may not solve the problem for long. Be prepared for additional work if the valve seats or other related pieces are worn. To help prevent the problem from reoccuring, I would recommend removing the tray under the engine to lower engine compartment temps in traffic. Changing the oil and filter more frequently than the owners manual suggests will help, too. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">

Jeff

Kevin -- I read the same article - I have 36K on my car and I don't drive in traffic but the PO may have. I'm afraid my next stop is a $4500 kick in the pants.
96P993 -- what finally stopped your CE light?

cmoss

All I can say is that my carbon build up problem was fixed by a top end rebuild. I just got luck and didn't have to shell out the $$$'s. The repair was done by a dealer so you can imagine what it would have cost out of pocket.

fbfisher

My shop recommends the BG44K prior to the oil change.

Jeff

I'm not familiar with the "BG44K" can someone enlighten me? Thanks

96P993

Jeff here is some info on it.... <a href="http://www.bgprod.com/bgprofessional/bgproducts/autofuel.html" target="_blank">http://www.bgprod.com/bgprofessional/bgproducts/autofuel.html</a>

Rick Lee

OK, can someone give some info on the chances of Porsche picking up the cost of this? I've heard they do pick it up sometimes, but have no idea under what circumstances that would happen.

Randall G.

Hmmm. I thought "we" had decided a long time ago plugged secondary air injection was harmless, as far how the car runs. Mainly a problem with getting the car to pass emissions, and if you can figure out a way to trick the SAI code, you just keep driving.

Also don't remember ever reading (before Jim P.'s Excellence article) that the SAI light was indicative of bad valve guide seals.

Here's an example SAI cause/fix thread. Many more in the archives.

<a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic;f=3;t=007286" target="_blank">SAI Cause/Fix Thread</a>

96P993

Randall I agree with you for the most part. I think many have gotten to the point where the "CEL" automatically goes to valve problem or SAI. I would like to know what the code is when the SAI problem arrises....I have no doubt some of the check engine codes have to do with both of these but I cant believe all of them are..