Kirk - It will sound crazy basic, but check carefully the plug wire ends connected to the distributor. Your boggy and rough symptoms sound like a mis-matched cap and wire/cylinder issue.
Cheers,
Chris

Chris,

I was thinking the same thing, its easy to sometimes make a small error when you are dealing with all of the issues around a rebuild.

I've been a little tight for time so far this week but I double checked the following:

1. Plug wires & firing order are correct for both distributors

2. Set the engine to Z1 mark, and pulled both distributor caps to double check that the distributors were as closely aligned to #1 as the distributor gears will allow, and that both the primary & secondary are properly aligned. (Never hurts to double check!)

3. Let the engine idle for a bit and sprayed the plug wires with a little water to make sure there was no arcing. I didn't see any problems.

We have been getting some nasty weather here the last couple of days, and I haven't pulled off the rocker panel to get at the oil lines and see where my oil leak is coming from, so I havent done any more test drives yet. (There was a snow last night so its a skating rink outside)

Jason on rennlist mentioned that the knock check should read zero. On my next test drive, I will do another check of this with the hammer to see what numbers mine is reading. (Snow should be dried up here in a day or two)


Kirk

Kirk,
You can also measure resistance across the plug wires. They should be 2.8kohms to 3.0kohms, I think.

Another quick test would be to disconnect and ground out one of the coil electrodes at a time and see if it changes the way the engine runs / revs. It may isolate a problem with one cylinder, easier.

I read through most of the thread, but am not sure: did you do anything to the injectors? Any chance one isn't spraying properly or has a weak pattern?

You could always do a quick compression test. Removing the bottom plugs is pretty quick.

You did a beautiful job, by the way!

Doug

Kirk,
After a few miles on the engine, I hope it as good as it looked to be.
One of the mods you added was a set of, what appears to be aftermarket, exhaust valve covers. Was that done for show or to correct a leakage issue? If the latter, did it work? If done for the former - oh yes, they look nice.
Also, I noticed along the way that you were able to replace the flexible heat shield surrounding that short, flex section of the oil line, which connects engine return oil to filter. Pelican has informed me recently that this item is no longer available from any source they know of. Where did you get yours? Mustn't have that long back, as it looks in the photo to be new.
Not only was it a well thought-out project and one I hope you are proud of; but each one of us other 964 owners owe you a lot for sharing the experience as you did. Please add my name to those members already expressing sincere gratitude for the time and effort. Well done!
James

"Firesleeve" or "FireJacket" are common names for it, and is available through most race-parts companies like Pegasus or Coleman. I usually buy it from an aircraft parts supplier like Aircraft Spruce and Specialy Co in large bulk but you can probably get it cheaper in smaller lengths from Coleman or the like.

Thanks for the info Adam, I have now located it in the Aircraft Spruce catalog.

James,

The shield for the oil line was ordered from Sunset Porsche. They seemed to have no problem getting it. On the 89/90 964s the valve covers are magnesium. They tend to warp easily and leak. I replaced the lowers with the Billet aluminum ones to solve the problem. (Oh ya and because they looked cool. :) )

Kirk

I put another 200km on the car yesterday. The engine runs well but still feels boggy, particularly at lower rpms.

I hooked up the bosche hammer and it is still showing some knock occurring.

I ran the knock test about 10 times under varied driving and I am getting numbers between 0-8 knocks per 10000.

The injectors I left untouched except for changing the O-rings on them.
Any ideas? How do I isolate which cylinder is knocking?


Here is what I know:

I know its not due to high compression on the engine.
I know the dual distrubtor belt is ok, properly aligned and that both distributors are firing
I know the distributor timing is correctly aligned at the Z1 mark.
I know the distrubtors are both wired correctly to the right cylinders
I know the gasoline is fresh 91 Octane super unleaded
The rotors/caps/plugs were all replaced at rebuild time.

I don't believe it is due to cross firing in the plug wires. Spraying them with water caused no difference I could detect.

The changes I made to the engine at rebuild time were:
1. Cone filter
2. Cat bypass (with O2 sensor)
3. Cup Pipe
4. Updated manifolds from aluminum, to later plastic style


So what else could it be?

Here are the things I can think of:
1. There might be an aftermarket chip in the replacement DME I bought
2. An injector could be having issues causing a cylinder to run lean? (But wouldnt that cause a higher knock value?)

Anything else anyone can think of?

Kirk

Can the Hammer do a cylinder drop test? I used an old generic Bosch tester from the early 90s that would do that. That test could make sure things are working equally across the cylinders.

Maybe one of your knock sensors and is causing a problem and issuing false possitives? This could cause the computer to retard timing, which could cause the "boggy" feeling.
OR
I would think if an injector were having a flow issue, it could cause a lean condition which may contribute to a knock in a given cylinder. Maybe the cylinder drop test could provide some data as to which injector to focus on.

I have a Steve Wong chip for my '95 engine and the difference was dramatic, while remaining conservative with regards to timing, etc.
Doug

kirk,
Thanks for your reply. I have already ordered a length of Aeroquip fire sleeve from Pegasus. The largest ID I could find was 1.5 inch, and that will be tight. May not be able to slip it over the hose end fittings without damage. In that event I shall look to Sunset Porsche, as you suggest.
Yes, one of my exhaust valve covers has leaked too, in spite of carefully cleaning the surfaces and torquing to spec. Might I inquire just where you sourced those billet aluminum specimens. I only ever see then at 10k valve adjustments so don't care much about looks. Also the stock units have those nice clips for spark wires, so have been thinking of taking both of them over for surface grinding to level. Maybe the aluminum covers are a better bet in the long run. Do you coat the formed rubber gaskets with ThreeBond 1211, as I noticed you did on the chain covers? I have always put them in dry. Or does the billet cover use different gaskets?
Sorry for all the questions, when you are so focused on the knock issue, but you seem to have already worked out this leaking valve cover issue.
James

James,

All questions are welcome. I know plenty of people took time to answer mine!
The valve covers are from Imagine Auto, ( www.imagineauto.com ) they come with gaskets. I installed mine dry. I was thinking about drilling holes, and them tapping them to allow installation of the spark plug wire clips, but I was getting a little tired of engine work near the end and I didn't bother. I might do it when I check the valve lash at the 1000km mark. If your car is an 89/90 then you could always just replace the lowers with the 91+ aluminum valve covers on the bottom. Not as shiney, but I think they leaked alot less.

Doug,
I don't think the hammer can do that, but I wonder if I wouldnt get the same results from pulling the injector wires individually and seeing when the knock stops? I am trying to figure out in my head whether that would cause any motor problems or not.

Tomorrow I might open up the DME and make sure it doesnt have a chip in it that is setup for a higher octane gas than I am using. ( 91 octane is about the best I can get around here)

Kirk

Kirk, did you receive my PM's? I never saw an answer.

Regarding the knocking I would diconnect the injectors to one cylinder at a time and check if this makes a difference. I do see some knocking on my 3.6 fresh rebuilt with a stock chip but I know this is most likely due to the plugs being due for a change after 15k. It mostly happens when the engine is hot and I floor it at 3.5k RPM. The hammer can not do the drop test. It will show the actual spark advance though. This could be helpful to determine whether your chip is stock. What model number does the hammer read from the Motronic?

BTW, your knock count is well within Porsche's specification. As long as the adaptive knock control reduces the advance you should be fine.

Cheers,
Ingo

OK,

I removed the DME and opened it up to check the chip.
The chip is I believe the porsche factory one. Its numbered #1267355769
Correct? The DME had been opened previously.

I am not sure how well the chip from an '89 car is going to handle the heavier DMF flywheel to stabilize idle. (My car had its transmission replaced early in its history from the 89 SMF type to a later style DMF) But thats a different matter.

Any other ideas about what could be causing occasional detonation?

It snowed here again and the streets are a mess. So I haven't pulled the car out for any more test runs.


http://forums.pelicanparts.com/uploa...1161363096.jpg


Kirk

"Why does the factory repair manual say that you should buy new microencapsulated bolts for the knock sensors? Whats wrong with the old bolts and some locktite?"

Just to revisit this issue in your rebuild, you may be interested to know that Pelican, our host company, have been unable to obtain the microencapsulated bolts anyway. It would appear that locktite on the old bolts is the best approach for sure.
James

Kirk, yes, this is a stock Bosch chip. The hammer should be able to read out the code base number when it talks to the DME. It's a number like this: 964 618 124 0X where X is 0 - 4. This number is stored in the last part of the chip and tells you which code version the chip is. 03 is the most comon. BTW: If it is the original chip this number matches the part number on the outside sticker.

ingo

UPDATE:

I have now put about 1000km on the car, and so far it is running quite well.
I still get some low knock numbers from the Bosch hammer. I havent found a reason for it yet.

I changed the oil twice with regular 20W50 DINO Oil and now I am running Mobil 1 5W50 synthetic.

I had oil leaks on one of the oil lines at the thermostat housing and from the oil reservoir level sensor. Both of which I fixed on the last oil change, so for right now it looks like everything is dry.

There was some minor dripping from the cam shaft seal at the power steering pump, but it stopped as soon as the seal seated itself.

I also managed to get the longer wheel studs on the rear wheels with a little wider spacer.

Now i'm bored. I wish I had enough cash to get the bodywork done this winter. I want my car to be a widebody.


Kirk

If you are really looking for something to do...
 

Try this:

http://forums.pelicanparts.com/showthread.php?s=&threadid=169698&highlight=964+va rioram

You could get started using this...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&sspagename=STRK%3AMEWA%3AVR I&viewitem=&item=230051097253&rd=1,1

How is the powder coating, especially for the engine tray, holding up? I'm thinking about doing that, too.

As far as I can see the powder coating is holding up very well. I would recommend doing it.

I will be dropping my motor again soon to install a supercharger. I'll have a better chance to assess how well everything worked out then.


Kirk

bookmarked for later