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996 Engine low compression in one cylinder Smoke on initial startup
Need some advice... I have a 99 996 C4 100k miles. Runs great. Bought the car knowing it smoked at start up, suspected an AOS. Had leak down compression test done to make sure before replacing the AOS. Found compression down 22% in one cylinder. Borescope showed scarring on one cylinder. Smokes for about 30 seconds at first start up then it goes away. Does not seem to consume oil. Again, other then initial smoke on start up runs great. Does have CEL for secondary air pump fault. What should I do? Dealer says replace engine (way too expensive), Indy says live with it. Thoughts???
eh, some guy here drove with scored cylinders for like 30-50k miles or more and aside from burning some extra oil and the occasional smoking, it seemed to have no ill effects. Car will likely be down on power but I'd probably keep driving it for now.
I've owned a number of 996 and currently have another 99 with only 70k miles that is pristine. The c4 runs just as strong... can't see dumping 15k+ into it as i bought it to throw some snow tires on and run this winter. I bought the car CHEAP so I know you get what you pay for...
Need some advice... I have a 99 996 C4 100k miles. Runs great. Bought the car knowing it smoked at start up, suspected an AOS. Had leak down compression test done to make sure before replacing the AOS. Found compression down 22% in one cylinder. Borescope showed scarring on one cylinder. Smokes for about 30 seconds at first start up then it goes away. Does not seem to consume oil. Again, other then initial smoke on start up runs great. Does have CEL for secondary air pump fault. What should I do? Dealer says replace engine (way too expensive), Indy says live with it. Thoughts???
Scoring can't be that bad if the oil consumption is ok, if there is no noise, if there is no CEL.
Frankly with no CEL I want to suspect the compression test results. The DME constantly checks each cylinder for proper operation and a cylinder truly down on compression should have triggered a CEL and one or more misfire error codes.
So in this case I'd agree with your Indy: Live with it.
But maybe not before possibly taking care of the AOS. It would be the AOS that accounts for the smoking. The AOS doesn't have to be completely bad just sub-par and letting excesisve amounts of oil vapor through which collects as fluid on the intake walls and this then can oil maybe just one cylinder and you get a bit of smoking upon startup.
Oh and take care of that secondary air pump problem.
Need some advice... I have a 99 996 C4 100k miles. Runs great. Bought the car knowing it smoked at start up, suspected an AOS. Had leak down compression test done to make sure before replacing the AOS. Found compression down 22% in one cylinder. Borescope showed scarring on one cylinder. Smokes for about 30 seconds at first start up then it goes away. Does not seem to consume oil. Again, other then initial smoke on start up runs great. Does have CEL for secondary air pump fault. What should I do? Dealer says replace engine (way too expensive), Indy says live with it. Thoughts???
Which cylinder had the low compression? Is it the same cylinder that showed scarring? What are the exact compression numbers for each cylinder? Did they do a leak-down test on the cylinders? What did the spark plugs look like from the cylinders? What weight oil is in it? What is the CEL code for the secondary air pump fault? At 100K your AOS should be replaced. Have you pulled the TB to see how much oil is in the plenum?
Which cylinder had the low compression? Is it the same cylinder that showed scarring? What are the exact compression numbers for each cylinder? Did they do a leak-down test on the cylinders? What did the spark plugs look like from the cylinders? What weight oil is in it? What is the CEL code for the secondary air pump fault? At 100K your AOS should be replaced. Have you pulled the TB to see how much oil is in the plenum?
Why didn't you state the AOS reference in the form of a question?
I've owned a number of 996 and currently have another 99 with only 70k miles that is pristine. The c4 runs just as strong... can't see dumping 15k+ into it as i bought it to throw some snow tires on and run this winter. I bought the car CHEAP so I know you get what you pay for...
That's pretty much what I want to do with one, ideally with scoring too so I can get it cheap. From there all I care about is the 4 wheel drive somewhat working.
=)
Unless it's the AOS I'd run it and take it a little more easy on warming up. Unless you have or want to spend the money to fix it.
I'm talking to the service manager in an hour and I am going to get the answers to the questions posted...there was a compression and leak down done. Stay tuned for his response. I also talked to 3 Indys, all of which I know from PCA and all of which know their stuff. All said live with it. One suggested using a higher viscosity non synthetic oil and add some Lukas oil treatment...
The AWD works great, heated seats, back up sensors, nice side skirts... Just smokes on initial start up. Once warmed up it's fine.
Should have mentioned the smoke on start up is from the driver side... passenger side has the normal puff but the bulk is from the drivers side pipe...
so Cylinder 4 had a fouled plug and it was the one with the scoring, it's the only one they used the borescope on since the plug was fouled while the others were ok....makes sense since it's on the passenger side bank. I've attached a pic of the cylinder scoring. results of compression/leak down showed falsely high compression in cyl 4. 1- 155, 2 - 140, 3 145, 4-160, 5 - 165, 6-170.
$9k aprox for a new Porsche short block installed or sell it as is.
Or re-sleeve the cylinders...depending on how much you like the car. Or just deduct a re-sleeve job from your asking price and provide full disclosure to a new owner willing to take that on.
Main reason I bought it was to keep from driving my 07 Targa 4....
Thinking of dumping some Lucas into it and driving it...
here are some pics of the 996...
12-14-2016, 09:30 AM
996 Engine low compression in one cylinder Smoke on initial startup
