Hi Tom,

thanks for the feedback. Because the engine was cold i the values are OK – engine should run with this values on all 6 cylinders.

Could you please check these things:

• Is the exhaust system on the left free floating. Means maybe you have a clogged / blocked catalysator and the exhaust gas can't escape.

• Same for the intake. Please check if everything is free and nothing is in there - no air, no explosion.

• Check if all sparks ignite.

• If you have a tool to check if you have ignition on sparks when motor is running, please check that. In german it's called ignition lamp - don't know wthe correct english term is. It visualizes spark ignition.

Hope that helps or maybe get's you another idea what you still can test.

Regards and fingers crossed
Markus

PS: it's always a bit tricky for me to describe these things in english, because i don't always know the correct technical terms. If something is misleading, please ask.

I know it's 5 pages long and a lot to read, but a lot of your questions have already been answered by the OP.

It is too much to read. So here's a summary.

Bought a non-running 1998 Base Boxster with 96000 miles. stored in a barn in the desert south of Sierra Vista, AZ about 10 miles from Mexico. I could find no one in Phoenix or Tucson to go there and do a PPI.

Replaced:
Spark plugs
Spark plug tubes
Fuel filter
Fuel pump
Fuel sender unit
Fuel pressure regulator
AOS and J-tube

Fuel pressure test is 3.8 bars, no real leak down
Compression test numbers are above
Have spark at all spark plugs
Noid light shows all injectors firing
Corrected the vacuum leak at the intake manifold
Cleaned the MAF. Car will not start if MAF is disconnected

So at this point, I should have fuel, air, and spark. I have not tested the O2 sensors. No CEL is being thrown. Durametric shows no codes being thrown. I also have not cleaned the IACV or the throttle body.

I think that's about it. At this point, I'll install the new spark plugs I have and give it a go.

Tom; I think your compression numbers are way low. Even cold you should see 145 psi or more. Hot compression should be 180+ psi. Since plugs are out a simple test might be to get a helper and some chopsticks then with chopstick on top of piston mark chopstick at TDC then roll engine by hand and get BDC measurement all cylinders. Then compare to each cylinder.

What is the compression specification for the 2.5 liter engine? I've searched and searched. I see a post by Jake Raby that says it should be over 200. I see others by JFP that says around 145 and that the results should be within 15 percent of each other.

911monty. I like your suggestion. It's a test for a bent rod. I will have to find a patient helper. My wife doesn't mind cranking it over, but to get her to actually turn an engine by hand is a definite NO.

Lots of factors determine compression condition of motor of course but temperature, density, humidity and altitude all contribute. I think the numbers I gave are conservative for Arizona. Like I said with a failed AOS bent rods are a possibility. Then piston to dome height increases and compression decreases. Not trying to be pessimistic, just think I would want to eliminate this potential. Good Luck.

I believe 200+ is for the 3.2.
The 2.5 should see 140's cold. Your #'s are a bit low, but not too bad for a 2.5 with higher miles. What's important is the variation from one cylinder to the next (you want them within about 10% of each other).

I think your compression #'s look fine. Leak down?

Compression ratio on a 2.5 is 11.1. AT sea level this would be approx. 165 psi.

On a new engine. ;)
As sleeves, rings and valve seals wear, that number drops. A leak down test would probably support this.

Yes. But what is significant in this case is that the really low numbers are all on one bank which tends to be mechanical.

Still the question if the exhaust system is free - no clogged cats. Sorry, but this is a very important questions and i'm sorry if i overread that. Don't wan't to bore anybody.

Also the 2.5 has a variable valve system. So compression rate can vary. Even if they are lower / low on the left bank it should run on all cylinders. But if you listen to tada's video it only runs on 3 cylinders.

Regards, Markus

Thanks for all of the input. I ordered a exhaust pressure tester and will check for a clogged catalytic converter tomorrow. I will play around with finding TDC and BDC tonight. Thanks again, Tom

And by the way Markus, your English is excellent. Far better than my German could ever be.

Tom; You just need to find TDC #1 (timing mark) find piston top with chopstick through spark plug hole and mark. Turn crank 180 deg (BDC) and mark chopstick again. Then place chopstick into each cylinder and rotate making sure all pistons reach the same marks. It's not precision, just looking for major difference.

Have you checked the cam timing? My engine sounded just like your video when my bank 2 timing was off.

I had similar symptoms but not exactly. I got engine check light and it started dying whilst I was sat in traffic. I could rev it but as soon as I let off the gas it would either die or seems like its about to die. Problem turned out to be one of the solenoids, and fyi, it is quite expensive. I would try to check them out, although I'm not quite sure how.

Timing definitely occurred to me. I thought maybe the camshaft position indicator could be bad. But to check the cam timing, don't I need to get it running and check it with the Durametric?

Just read an article on cam timing. Can this be done without dropping the engine?

I can tell you from past experience that it is possible to check the cam timing without dropping the engine. Checking the timing only requires being able to rotate the engine to TDC and removing the 6 green plugs. I used the camera on my phone to take pictures of the cam notches so it was easier to see.

This post had some good information that might be useful:

http://986forum.com/forums/performance-technical-chat/26418-diy-setting-cam-timing-m96.html

Yes -pin TDC @ the crank pulley, remove blue camshaft plug (you will need new one) on offending cylinders and check slots on end of camshaft lines up with marks as per article.

Timing check results
 

Before I got the chopsticks out and started measuring cylinder stroke to check for a bent rod, I popped the camshaft plug on bank 2 and looked at the timing. A couple of pics are shown below of the crank at TDC and the position of the camshaft. The phone camera was as level and as close as I could get. Imagine taking these with a 35mm camera? So, what do you all think? Pretty close.

https://flic.kr/p/GkziwW

https://flic.kr/p/FysP4r

This is a great picture of the intake cam. Could you post a picture of the exhaust cam so to see if the notches are straight up and down?

See post:

http://986forum.com/forums/performance-technical-chat/26418-diy-setting-cam-timing-m96.html

Hi Tom,

to me that looks OK. Even there is a little deviation, the engine should run - and not in the way it runs on your video. Also the problem in general isn't a bent crank at this engines. Mostly it's a chain that sprung over – caused by a failed chain tensioner, broken chain ramp or anything related to ims mechanism.

Do you have any infos from the preowner how the car stopped working and what he or his workshop did to fix the problem?

From the symptoms i'm still on the clogged catalysator or intake side.

Regards, Markus

Hi Markus,

I'm just following ideas and eliminating variables. Below is what I bought to check the catalytic converters. Screws right into the O2 sensor holes. But, I'm running out of time tonight and I will save it for tomorrow.

As for the previous owner, he bought it in Glenwood Springs, Colorado at a used car lot in July 2015 for $8000 and had 94368 miles. Drove it to Sierra Vista, Arizona. Parked it. Would not start. He tried changing plugs. It was obvious his girlfriend (the actual owner on the title) had had enough of it. Their prospects were towing it to a Porsche dealer or Indy in Tucson, 100 miles away. So getting history from them was useless. They didn't know it had a toolkit (I needed the tow eye for the flatbed). I ran carfax and autocheck. 7 previous owners. Was a lease car for its first four years with 4 owners in those first four years.

Tom

P.S. Before this is all over, I think I will own every specialty test tool available. It would be great, but my other cars actually run dependably and need little maintenance. I guess I will be setup for servicing Porsches for life.

http://986forum.com/forums/uploads02...1461293260.jpg

One last update. Did the chopsticks test. Difference between TDC and BDC on all six cylinders was 2.25 inches. No variance.

So at this point, I'm going to rule out a bent connecting rod and bad timing on bank 2.

On to cat testing tomorrow.

Thank you all for all your help and suggestions. I'm learning more than I ever thought I would.

Best regards, Tom

Catalytic Converter Testing
 

Well I got the appropriate O2 sensors out and tested in front of and back of each cat. The gauge read almost zero on all four openings, so I will assume that back pressure is not the problem. On to checking for intake restrictions. Something may be blocking that side. Hoping it's not something long dead.

Hi Tom,

well zero means, that something is blocked. Right?

Please also check if the left side header and all connections points of the exhaust system on that side for new gaskets and screws - so the question is if some parts were removed lately. I've seen idiots that put in gaskets without holes. And because we don't know what the workshop did… ;)

Regards, Markus

Good result! Might check your measurement though. 2.5 liter has stroke of 72mm or ~2.8".

Hey, you said approximate!

No, it actually means the cats are free flowing. The gauge reads pressure in psi. I saw puffs on the gauge at all four O2 sensor holes but the pressure was negligible . If the cat was plugged, the readings in front of the cat would be higher.

So I'm running out of ideas. I'll go ahead and remove the throttle body and intake manifold, clean it, and look for any air restrictions to bank two and any vacuum leaks that may be present after getting the parts out of the way.

Any chance this could be a bad DME?

Maybe I missed it, but did you check the cam timing already from the link that "muscatty" posted?
The check is easy enough to do with the engine in.

http://986forum.com/forums/performance-technical-chat/26418-diy-setting-cam-timing-m96.html
http://i156.photobucket.com/albums/t...1/_MG_7828.jpg

The timing on bank 1 was right on. I posted a pic of bank 2:

Hello tada,

i have a wiring diagram for the 99 986 dme. It's too big to post it here.

Looks like every ground point for each fuel injector runs seperately, but has an internal node.

The ignition has 2 ground points on the DME. But they are connected. The wiring loom runs to one central ground node, but there is a wiring running to each. Maybe a broken wiring loom cable? Did you recheck the ground connection on each ignition coil?

Don't know DME outs for one bank could be shot all at once. In general each out has his own power transistor.

If you pm me your e-mail address, i can send you the wiring diagram.

Regards, Markus

On the vacuum trail ...
 

Going through the vacuum system for a bit. I have a question about the secondary air injection pump. I do not hear any sound coming from it during cold startup (not like I ever have warm startup). I left my windows computer at work, so my Durametric is helpless right now. Can a failed SAI pump cause this bad a problem? Thanks, Tom

Hi Tom,

in my opinion the engine should run proper just with a failed SAI. Maybe it will run too fat, but that wouidn't lead to a not working cylinder bank. Also the SAI blows air into the complete intake system – not only in one cylinder bank side.

Could a failed o2 sensor lead to a problem with one cylinder bank. I would say yes, but i don't think it could block the bank from running. And that is what it sounds like.

There must be a more fundamental problem.

Regards, Markus

I finally found time to remove the throttle body and intake manifold. I expected to find it filthy, but instead it is pristine clean. Strange. I am still hunting a vacuum leak. When taking off the intake manifold, the vacuum tube to the fuel pressure regulator snapped at the point where it enters the "bellow" of the intake manifold. It may have been weak or leaking to begin with. I'm still going to clean the IAC valve and do some more smoke testing on the vacuum parts

Interesting.
If one vacuum lie is so brittle it cracked ,what about all the others if they are the same age & have endured the same heat cycling ?
Pelican sell a vacuum hose kit but I had wanted to find a set that are a better grade of plastic. In theory silicone may work for the small diameter hoses if you get a thick wall? It has a tendency to collapse under high vacuum when hot. So the cheapo EBAy ,thin wall silicone hoses would be a bad choice.
For smoke testing the vacuum system I recent;y upgraded to a better quality paint+can+baby+oil system.It works well because it pushes ut a lot of smoke for a long period consistently.
Thanks for letting us all follow your progress.

I'll replace them all if I could find that kit. I've searched for hours for the part number of the rigid vacuum line I need that goes from the intake manifold to the fuel pressure regulator. Porsche Atlanta shows it on a diagram as part 16, and then does not list it. Pelican has rigid vacuum line sold by the meter that is listed as 4.0 x 1.0 mm. If anyone knows the part number, I would appreciate it. Otherwise off to my local Porsche dealer.

For the hard line, try Sunset??? They have an excellent rep for helpfulness.

Hello tada,

is the part you're looking for on the chart, or am i on the wrong chart. If it's on the chart, which number has it. Could you alternatively link to the chart from Porsche Atlanta. Than i can look for the parts number.

Regards, Markus

http://986forum.com/forums/uploads02...1462795675.jpg

Thanks Markus and Gelbster. I was finally able to find the part number for the vacuum line - 00004320501. I appreciate the help, Tom.

Just throwing this out in an attempt to be helpful: any chance that the variocam solenoid on that bank has failed? And if it did, would it throw a code or light the CEL?