Jump to content

The RennTech.org community is Member supported!  Please consider an ANNUAL donation to help keep this site operating.
Click here to Donate

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

Cylinder misfire, gasket blown inside bore


Recommended Posts

Interesting borescope session from cylinder #4 https://vimeo.com/80341238

As you can see it contains white "fluffy" stuff which I suspect is the main gasket. Note the time after 40 seconds when I go through the stuff, it is quite soft. Plugs looked fine, brown colored, all cylinders look OK too in my opinion, except that gasket stuff. Other cylinders looked fine, but #6 had also small amount of the same stuff that cylinder #4 had.

I cleaned my throttle body to figure out small oil leak. After I was done I decided to try it out and noticed that my idle is now better. Engine worked fine for 15 minutes, after that I revved it a bit to 3000rpm for a couple of times. Finally when the engine was warm I pushed the pedal 100% down for a fraction on second gaining almost 4000rpm, immediately after that I got rough idle and noticed that some cylinder(s) are not firing. Loss of power / throttle was noticeable too. After 10 seconds I got knocking (around 5 per second) + CEL, then after 10 seconds CEL flashing and decided to stop the engine. Durametric shows cyl 4 misfire. After that I took coils and plugs away and grabbed my borescope. I was not happy what I discovered from cyl #4 :-(

Any opinions is the engine done or are there any viable options to try out?

911 Carrera 4, cabrio, 3.6L, 2004

Updated picture link here:

https://www.dropbox.com/sh/rlzlul4q7n58ui6/-tP8T4hMey/Paper-inside-engine

post-93239-0-70580300-1385445459_thumb.p

post-93239-0-17750200-1385445462_thumb.p

Edited by Domiac
Link to comment
Share on other sites

  • Moderators

Interesting borescope session from cylinder #4 https://vimeo.com/80341238

As you can see it contains white "fluffy" stuff which I suspect is the main gasket. Note the time after 40 seconds when I go through the stuff, it is quite soft. Plugs looked fine, brown colored, all cylinders look OK too in my opinion, except that gasket stuff. Other cylinders looked fine, but #6 had also small amount of the same stuff that cylinder #4 had.

I cleaned my throttle body to figure out small oil leak. After I was done I decided to try it out and noticed that my idle is now better. Engine worked fine for 15 minutes, after that I revved it a bit to 3000rpm for a couple of times. Finally when the engine was warm I pushed the pedal 100% down for a fraction on second gaining almost 4000rpm, immediately after that I got rough idle and noticed that some cylinder(s) are not firing. Loss of power / throttle was noticeable too. After 10 seconds I got knocking (around 5 per second) + CEL, then after 10 seconds CEL flashing and decided to stop the engine. Durametric shows cyl 4 misfire. After that I took coils and plugs away and grabbed my borescope. I was not happy what I discovered from cyl #4 :-(

Any opinions is the engine done or are there any viable options to try out?

911 Carrera 4, cabrio, 3.6L, 2004

As the head gaskets on these engines are multilayer steel, and never fail, I doubt that is head gasket material.

More likely, that is a build up of dried coolant from a crack area. Time to run a leak down test.

  • Upvote 2
Link to comment
Share on other sites

As the head gaskets on these engines are multilayer steel, and never fail, I doubt that is head gasket material.

More likely, that is a build up of dried coolant from a crack area. Time to run a leak down test.

That being said, it is definitely not from the head gasket. I'd be hesitant to start the engine due to knocking sound and foreign stuff in cyl #4/6. Safe to say there is a leakage somewhere, could you help me to understand why a leak down test would provide useful information?

Before I haul the engine to a shop and start burning some serious $$$, I'd appreciate a lot for any comments regarding how I could assess the situation better myself. I could drain coolant + oil and check for intermix. Then drop the engine and open cylinder head, at least that should tell is the engine salvageable or not.

The car has never smoked, even the tailpipes are clear as a sky, same thing when this problem happened. 85k miles, original water pump (yes, new one is already coming), coolant level now below minimum(!). At least that is good that this problem happened on the front slope of my garage when I was warming up the engine and not while I was driving in the freeway.

Much appreciated JFP for your comments!!

I guess my driving days are over for a while, this really really sucks :unsure:

Edited by Domiac
Link to comment
Share on other sites

  • Moderators

As the head gaskets on these engines are multilayer steel, and never fail, I doubt that is head gasket material.

More likely, that is a build up of dried coolant from a crack area. Time to run a leak down test.

That being said, it is definitely not from the head gasket. I'd be hesitant to start the engine due to knocking sound and foreign stuff in cyl #4/6. Safe to say there is a leakage somewhere, could you help me to understand why a leak down test would provide useful information?

Before I haul the engine to a shop and start burning some serious $$$, I'd appreciate a lot for any comments regarding how I could assess the situation better myself. I could drain coolant + oil and check for intermix. Then drop the engine and open cylinder head, at least that should tell is the engine salvageable or not.

The car has never smoked, even the tailpipes are clear as a sky, same thing when this problem happened. 85k miles, original water pump (yes, new one is already coming), coolant level now below minimum(!). At least that is good that this problem happened on the front slope of my garage when I was warming up the engine and not while I was driving in the freeway.

Much appreciated JFP for your comments!!

I guess my driving days are over for a while, this really really sucks :unsure:

If you have suffered a cylinder head crack, which is not that uncommon, you can often (but not always) catch this with a leak down test which pressurizes each cylinder while the piston is at TDC and observes percentage leakage. Quite often, cracked cylinder heads will allow the air from the test to bubble into the cooling system as well during the test, which is another confirming data point. If you suddenly find a cylinder or two that jump up over 10% leakage, they would be your suspects. You can also pressurize the cooling system (using a hand pumped cooling system pressure tester) to see if it will hold pressure, which is working from the opposite side of things:

crackedhead996.jpg

You may or may not experience an intermix with this kind of problem, but it is always worth checking the oil and coolant.

  • Upvote 1
Link to comment
Share on other sites

  • 2 weeks later...

Solved it!

I managed to pull part of that stuff out near the intake / exhaust valves through the spark plug hole and oh boy do I feel stupid now. I am 99% sure that this stuff is the same paper towel that I used to cover the air intake while taking off the throttle body. ARGH.. It all makes sense since misfire issue started after I cleaned the throttle body, let the car run fine for 15 minutes to warm up, all good, but when I hit the throttle 100% for a few hundred milliseconds gaining 4000rpm and a huge suction which apparently took this paper from air intake inside cylinder 4.

Now the real joy starts. How to clean this up properly? Is there any chemical that I could reasonably safely use to break down this paper from air intake all the way to exhaust? Carb cleaner / acetone breaks this paper down good but I'd be really hesitant on spraying such stuff inside cylinders, even if I apply oil there manually, it does not sound right.

I hope the rings or valves have not suffered from this paper gunk. I am going to turn crank manually in order to get exhaust valve open on each cylinder, then put compressed air inside each cylinder, using a leak down tester unit, and try to blow all that stuff into exhaust. Another option is to get all plugs out and blow compressed air to intake.

Wont start this baby until I get experts opinions from these forums. As always, any ideas appreciated!

Edited by Domiac
Link to comment
Share on other sites

Just see these two screenshots: the first one has two pieces of paper. Lower right is what I managed to snatch from the cylinder, upper left is a piece of paper ripped of from my garage paper towel holder.

Updated picture link here:

https://www.dropbox.com/sh/rlzlul4q7n58ui6/-tP8T4hMey/Paper-inside-engine

Edited by Domiac
Link to comment
Share on other sites

  • Moderators

Solved it!

I managed to pull part of that stuff out near the intake / exhaust valves through the spark plug hole and oh boy do I feel stupid now. I am 99% sure that this stuff is the same paper towel that I used to cover the air intake while taking off the throttle body. ARGH.. It all makes sense since misfire issue started after I cleaned the throttle body, let the car run fine for 15 minutes to warm up, all good, but when I hit the throttle 100% for a few hundred milliseconds gaining 4000rpm and a huge suction which apparently took this paper from air intake inside cylinder 4.

Now the real joy starts. How to clean this up properly? Is there any chemical that I could reasonably safely use to break down this paper from air intake all the way to exhaust? Carb cleaner / acetone breaks this paper down good but I'd be really hesitant on spraying such stuff inside cylinders, even if I apply oil there manually, it does not sound right.

I hope the rings or valves have not suffered from this paper gunk. I am going to turn crank manually in order to get exhaust valve open on each cylinder, then put compressed air inside each cylinder, using a leak down tester unit, and try to blow all that stuff into exhaust. Another option is to get all plugs out and blow compressed air to intake.

Wont start this baby until I get experts opinions from these forums. As always, any ideas appreciated!

Boy, you have come up with a real gem of an issue. Rather than trying to rotate the assembly or blow the bits out, which may worsen the problems, probably your best bet short of pulling the cylinder head is going to be inserting a bore scope into the cylinders to see what is actually in there and where it is sitting. Then it is going to be a matter of jury rigging some retrieval tools (copper wire with double stick tape on the end, etc.) to go after what you find. It is going to be slow and tedious, but I think doable without dropping the engine.

Once you get everything out you can find, I would still run a full leak down to make sure everything is OK.

  • Upvote 1
Link to comment
Share on other sites

Boy, you have come up with a real gem of an issue. Rather than trying to rotate the assembly or blow the bits out, which may worsen the problems, probably your best bet short of pulling the cylinder head is going to be inserting a bore scope into the cylinders to see what is actually in there and where it is sitting. Then it is going to be a matter of jury rigging some retrieval tools (copper wire with double stick tape on the end, etc.) to go after what you find. It is going to be slow and tedious, but I think doable without dropping the engine.

Once you get everything out you can find, I would still run a full leak down to make sure everything is OK.

Thanks. It's going to be hectic next two months for me in the Silicon Valley, but I'll get back to this during February when I got more time.

Clutch / IMS work is needed so I will drop the engine, take my time and clean this up the right way. Will remove exhaust and intake components to gain the best access, use borescope and a strong vacuum cleaner attached into tiny custom rubber hoses with various angles on the end. I'd vacuum rigorously from both sides (intake, exhaust) from all cylinders, inspect with borescope, turn crank a bit so that valves open, and start over again with the vacuuming all cylinders.

Last night I had the exact same thought that you had, using compressed air is perhaps not the best idea. It might even force this stuff against cylinder rings.

Will post more pictures of this once above is done. Then I have to carefully consider would it be safe to start the engine or should I go even further and remove cylinder heads, inspect valves / lifters / springs before engine is started.

Yes, it was me forgetting that piece of paper there and starting the engine, not my neighbor, idiot brother or mother-in-law.. :cursing:

PS. Your idea of using copper wire + adhesive is a good one too, thanks!

Link to comment
Share on other sites

  • 3 months later...

Gentlemen,

Finally I got the time to work with my 996. Dropped both engine and transmission, took off all intake parts and with lots of time, patience and some hand made tools I managed to get almost all of the paper out. Had to turn the crank in order to get intake and exhaust valves open and retrieve paper both from intake and exhaust. Have to say that some of that paper was really hard stuck on the intake valves (Cylinder 4 only), most of it was on intake tube just before the intake valves. I am confident that I can get it all out, only one half inch long paper still remains on cylinder 4. After the last paper piece is out, I'll use my borescope with 45 degree mirror to inspect all the cylinders once more.

Finally, I'll perform a leak down test for every cylinder. Test will be performed cold, but I am only interested of any variances between the cylinders. I truly hope that all cylinders give similar results, especially that the cylinder #4 does not stand out from the crowd.

Updated picture link here:

https://www.dropbox.com/sh/rlzlul4q7n58ui6/-tP8T4hMey/Paper-inside-engine

Edited by Domiac
Link to comment
Share on other sites

  • Moderators

Gentlemen,

Finally I got the time to work with my 996. Dropped both engine and transmission, took off all intake parts and with lots of time, patience and some hand made tools I managed to get almost all of the paper out. Had to turn the crank in order to get intake and exhaust valves open and retrieve paper both from intake and exhaust. Have to say that some of that paper was really hard stuck on the intake valves (Cylinder 4 only), most of it was on intake tube just before the intake valves. I am confident that I can get it all out, only one half inch long paper still remains on cylinder 4. After the last paper piece is out, I'll use my borescope with 45 degree mirror to inspect all the cylinders once more.

Finally, I'll perform a leak down test for every cylinder. Test will be performed cold, but I am only interested of any variances between the cylinders. I truly hope that all cylinders give similar results, especially that the cylinder #4 does not stand out from the crowd.

996-engine_drop.png

996-paper1.png

https://www.dropbox.com/s/dg6qm8srar6bpx7/996-paper1.png

https://www.dropbox.com/s/ld82xpzp0b877r0/996-engine_drop.png

Good luck with this project, it is one that I do not envy. Keep track of what works to get the paper out and what does not, I'm sure someone else will do this again sometime, and you will have literally "written the book" on how to deal with it.

Link to comment
Share on other sites

what I might try is blowing compressed air into the spark plug and carefully opening up one cylinder at a time via the crank pulley.

Get yourself a leak down test fixture (you'll need it anyways to insure you did not bend any valves)

At least that way anything that does loosen blows out.

I'm wondering if there is anything that you can use to help dissolve the towel that won't make things worse (either by adhering the towel to the valves,

or washing out the cylinder or what not.

mike

Edited by txhokie4life
Link to comment
Share on other sites

  • Moderators

what I might try is blowing compressed air into the spark plug and carefully opening up one cylinder at a time via the crank pulley.

Get yourself a leak down test fixture (you'll need it anyways to insure you did not bend any valves)

At least that way anything that does loosen blows out.

I'm wondering if there is anything that you can use to help dissolve the towel that won't make things worse (either by adhering the towel to the valves,

or washing out the cylinder or what not.

mike

Problem is that the blue shop towels are incredible strong and designed not to easily fall apart. Good for wiping off parts, bad for trying to get out of the cylinder bores.................

Link to comment
Share on other sites

I'm currently waiting for parts to complete a water pump and oil filler tube replacement session. Just this afternoon - before I saw this thread - I was stuffing a blue shop rag in the plenum to keep bad things out, and I had a bad vision about forgetting it somehow. :eek: Wow.

OK, so this thread so unnerved me that I had to find an alternative to the rag I had stuffed in mine....turns out that those plastic promo cups fit snugly enough to act like a big plug and not interfere in the work. It's also impossible to refit the t/b with it in place.

CupPlug75.png

Edited by steve20186
Link to comment
Share on other sites

Problem is that the blue shop towels are incredible strong and designed not to easily fall apart. Good for wiping off parts, bad for trying to get out of the cylinder bores.................

Once I have the time, I'll write a separate thread, include good pictures and tips on how to remedy the situation. In the mean time, please PM me if you need tips, hope not :-) Right now I'm working on IMS, RMS, clutch and checking out bunch of other stuff.

All in all, I managed to get everything out, without the use of compressed air or e.g. flushing cylinders. And yes, I have a leak down tester and will run it through all cyls and compare results to each other.

Thanks again everyone!

PS. Some admin could rename this topic "Cylinder misfire, forgot shop towel inside bore".

Link to comment
Share on other sites

  • Moderators

Problem is that the blue shop towels are incredible strong and designed not to easily fall apart. Good for wiping off parts, bad for trying to get out of the cylinder bores.................

Once I have the time, I'll write a separate thread, include good pictures and tips on how to remedy the situation. In the mean time, please PM me if you need tips, hope not :-) Right now I'm working on IMS, RMS, clutch and checking out bunch of other stuff.

All in all, I managed to get everything out, without the use of compressed air or e.g. flushing cylinders. And yes, I have a leak down tester and will run it through all cyls and compare results to each other.

Thanks again everyone!

PS. Some admin could rename this topic "Cylinder misfire, forgot shop towel inside bore".

Good to hear you got it all out, must have been a fun project. :thumbup:

Link to comment
Share on other sites

Had some time to perform a quick leak down test for two cyls. However the test was done cold meaning that the engine's temperature was around 25C / 80F. Also there has not been any oil in the engine for quite some time. I have slowly cranked the engine by hand, only clockwise, about 10 cycles.

As a reference, cylinder #1 lost only about 10-15% @ 90 PSI (not obvious from where) but cyl #4 lost about 65% @ 90 PSI (it was clear that the exhaust valves leak). Even if this was performed cold and there is not much of oil inside the cylinders, I assume that the difference is substantial and it worries me quite a bit. I tested cyl #4 twice, cranked it full cycle one more time, same result.

The thing is that almost all of the paper was stuck on the intake valves of cylinder 4, I would have thought that the intake valves leak if anything. But the lost pressure for cyl #4 comes out from the exhaust valves. If I am in luck, there's still some burned up crap on the exhaust valves and I am able to clean it a bit more with some chemical. I am fairly certain that there is no more any paper as I did a very thorough borescoping session for all my cyls using camera without mirror and also with a mirror with multiple angles. Any stuff that remains on cyl #4 exhaust valves would be burned up soot.

I think my options are:

1) clean exhaust valves on cyl #4 ?

- is there a spray or such that might remove the soot and help my exhaust valves to seal better?

- should I also tilt the engine 15 degrees so that the stuff I spray to the exhaust valves does not go past piston rings, instead gravity will make it come out?

2) haul my engine to a shop and let them check both heads and all valves?

3) start it up, if it runs good, let it warm well and then try to burn gunk by driving a trip on a freeway?

4) try something else?

PS. I once lost my camera mirror inside cyl #3, it sure was a fun 2h trying to get it out without violence, but eventually I did it. I'll perform leak down for all cyls later when I have more time to work with my car and update results here. Also add pictures of my borescope sessions, they are fun to watch.

Thanks!

Edited by Domiac
Link to comment
Share on other sites

The rag, or all your prodding and poking may have loosened some carbon that's now stuck in the seat. If you are sure you got the crap out, I'd probably fire it up and see what happens.

Yes, that is my thinking as well, it is likely that there is plenty of carbon pieces everywhere. Even vacuuming from the exhaust port might change the scenario.

Would it work if I if?

1. open the exhaust valves

2. attach strong shop vacuum to exhaust port

3. spray some chemical through spark plug

=> chemical should run right towards the exhaust valves

Note: I have a good access both to intake and exhaust valves as I have removed all intake and exhaust parts.

If so, what kind of chemicals would you recommend? There's plenty of stuff out there that you can add to your fuel and run the car but this is a bit different scenario as I do not have to run it through fuel system, instead I can apply the product directly.

Thank you all again!

Link to comment
Share on other sites

  • Moderators

If you feel you have carbon bits holding an exhaust valve open and causing the leak down issues, I would try just starting it up. Anything sitting in the exhaust valve or runner area is going to get blown into the exhaust system as soon as the engine fires. Spraying chemicals into the exhaust port is going to force the carbon bits into the cylinders where they could get down along side the pistons and potentially score the walls; I would try not to go there.

  • Upvote 1
Link to comment
Share on other sites

If you still have it all apart, I would probably try one last blow in the intake and suck out exhaust while you rotate the motor through a complete cylinder cycle. There will be some overlap at some point where the air will pass through both, so maybe find that point and keep it there for a bit.

All in all, I'm with JFP - I wouldn't use any chemicals either - especially if you are then running those fumes through a vacuum cleaner. Flammable chemicals and electric motor sparks can make for some good YouTube videos.

Link to comment
Share on other sites

Thank you again, I understand the concern on using chemicals, I definitely do not wish to ruin my cylinder coating or rings.

One last proposal, would you feel that the following would be a wise move?

1. spray oil through the spark plug inside the cylinder

- goal is to let the oil "wet" the cylinder head, but not to flood it

2. let it rest there for a day

- hoping it will break down and remove some of the paper residue / carbon from the cylinder head

3. vacuum from the exhaust port

- oil's viscosity would snatch removed paper residue / carbon

I'd simply like to maximise my chances on getting everything out before I start the engine.

Borescope tells that cylinder walls are clear as a sky, it is the cylinder head valves that have residue.

Edited by Domiac
Link to comment
Share on other sites

If you've been running solvent or carb cleaner through the valve ports and cylinders and If it's as clean as you say, then maybe some light oil would be in order to get some lubrication back in there, but if not then I would leave it dry. I would think that from a "clearing out" standpoint, dry is better.

  • Upvote 1
Link to comment
Share on other sites

If you've been running solvent or carb cleaner through the valve ports and cylinders and If it's as clean as you say, then maybe some light oil would be in order to get some lubrication back in there, but if not then I would leave it dry. I would think that from a "clearing out" standpoint, dry is better.

I have only sprayed a tiny dosage of oil to each cylinders, no other chemicals. It seems that the oil is actually braking a bit of the gunk on my cylinder head on the area right next to my valves. Experimenting with a bit of oil more and vacuuming from exhaust port, taking it slowly.

Thanks Steve and JFP.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.