running very rough sitting still
 

Hi,
Can any one give me some ideas on why on my way to work this morning I was driving thr car and at a light all of a sudden the car stared to mis and act like it wanted to stall out and when I wen to take off it wa ould miss and skip like a plug was off or some thing.

I recently have changed the timing belt & tensioner to Pk type also have repalced the rotors and caps and plugs, no new wires though, The car started runnig slightly rough before i did alll of this that is why I did it all, it had one big miss and the tension ligh came on so i never started or ran the car until after I had done all of the things above.

Now the car stars fine but runs very rough at idle and then once you get it up to speed it seems to run smooth again.

I did check my wires at night to see if any sparks were visible and none were so I assumed the wires were Ok, and throwing 200 or more for wires with out knowing seems like a big risk.

Any ideas on what it might be?

Thanks Tony H.:surr:

check the relay connections and the fuse tips for corrosion any relays that have corroded pins should be opened and inspected for corrosion internally. My guess is that you might need a new set of wires if the wires you have have crumbling outer sheathing then its time to invest in a good set of wires get the best set I suggest Beru with the new plug ends.
Also clean the hot post connections and open the back of the 14 pin connector to see if there is any insulation damage

OK,
I may sound stupid and iIwould love to do all you have mentioned, byut I am somewhat new to the machanics of this car so can you tell me more details on what and where the relays and fuse tips you are taliking about may be located to check?

My wires do not appear to be be crumbling on the ouside at all, and the last thing you mention is to clean the hot post then check the 14pin for insulation damage where is that pin on the car and the hot post as well (do you mean on the batttery?)

I know all of my question may sound stupid but I am learning more and more as this car breaks me? this is an 86 model if that makes a difference in what I am asking?

Thanks Tony H.

Sorry about the mis-spelled typing but I hope the questions are understood?

Does any one think that maybe it is possible when I put the belt on I might have not but the belt on the proper tooth of the cam gears?, If so how would I know, I marked everything and used the flywheel lock but it had slipped off once and I had to re set it to 45 degress before I continued.

From the time I first finished the belt and tensioner it seemed slighly off running wise but then smoothed out over time? Now it is worse than ever?

I feel like something may be wrong here I do not here any knocking sounds, I do here a ticking sound in the top right side of the engine which has always been there.

Should I take everything off again and check the marks on the cam gerars ( what a Job) or would the car not run at all if it was wrong?

The missing thing has prgressively gotten worse and worse aver the last week or so. I thought it was just the caps and rotors so i changed them now it seems very bad to me.

Tony H.

Hi Tony since your a member you can go to your edit avatar and add your car model year and trans type this way it will be easier to diagnose any problems you might have .
That said since your asking nthese questions first lets start here.
Go to 928gt.com find page 2 then click on tips and links find the fuse relay chart and print one off, keep it in the car.
Then go to your car and disconnect the ground point in the hatch area. clean the connection point with an eraser, make a cover for the end of the ground strap (I use cardboard folded over)and put it on the end , this to prevent the strap from making contact with chassis.
Next remove the spare tire, open the battery cover and remove both of the terminals remove the ground wire first and clean every connection, leave the ground strap off.
Then go to the PS footwell and remove the floor mats then lift up the wooden cover at the front of the footwell.
You will find a fuse/relay panel here. (AKA CE panel).
Just before lifting the wood cover look up above this and see if you can find any water drip marks these can be from the bottom blower box leaking water onto the CE panel, this is where the corrosion will start.
With your fuse relay chart inspect every fuse and clean the ends,use the pencil eraser, the ink side works better to clean the ends, if you find any fuse that not the correct size or thats corroded it might be best to replace the whole set, (use good quality fuses not the harbor freight fuses).
After the fuse inspection make sure to leave out any fuse thats not indicated there may be 2 or 3 that should be empty.
Then remove each relay make sure they have the correct part number on them and take a picture before you do this so you have a reference.
Any relay that has corroded pins should be opened and inspected, you can use a thin strip of 600 grit paper to clean the contacts, then clean the pins and install the relay.

The hot post is under the hood on the PS just in front of the shock tower it should have a cover on it if not then order one for 1988 S4 ,also you need a screw on stud cap to hold the cover on .
Get an 11mm wrench and remove the stud then you will need to clean these lugs with the eraser, if you find any wires that have shredding insulation the you need some heatshrink to repair these wires usually the fat red or faded to yellow/brown wire will require this, (HF sells heatshring kits).
After the stud connections are clean you will also see connector just above the stud connection, this is the 14 pin connector, pull it apart and inspect the pins for corrosion, open the back of the top portion of the connector and inspect for damaged insulation, be careful the pins dont slip out of the housing while doing this.
Once everything is clean put it all back together.
Jack up the car on the front ( use jack stands)then go under the engine to the PS of the block you will see a thick ground wire from the chassis to the block remove each side and clean the connections.
Also inspect/ clean the starter connections and make sure the harness isnt rubbing on the sway bar or the oil pan.
Next look at each coil and make sure there is a thicker black wire (the ground point for the ignition system) that goes from the head to the mounting bolt on the coil, these wires usually break or are not put back on after belt work is performed
After all of this then you can reconnect the battery, and roadtest your work

Tony I cannot answer your questions but I can tell you Search is your friend. all of your questions can be answered through the experiences of others. At the top right of the 928 forum there is a search option. Put in key words like "hard start" or "rough cold idle" etc. What helped me immeasurably was to read every post in the "New Vistor....." thread at the top of the 928 forum. It is full of suggestions, information and specific maintenance and repair procedures. Unfortunately, your symptoms may be the cause of a simple thing like a loose relay, or it could be a compounded result of several little things. After reading those posts I found I could understand 80% of the responses provided to questions by others. For example I then knew what the CE panel was, or the hot post.

Good luck and I know others here will offer more advice to help you track down and repair your issue.

EDIT: See mrmerlin beat my response with great specific instructions. The magic and goodwill of this forum is fantastic.

Now about your belt question.

Warning dont run the engine anymore till you verify the belt timing

I would turn the crank to TDC , and inspect the cams to see if they both line up correctly, you can look down the tops of the covers to do this but I would recommend that you remove the PS top cover to inspect the belt, you should be looking at the front edge of the belt for wear and testing the tension of the belt.
The alignment marks are on the front of the round holes in the tops of the covers they are little angles that should line up with a square cutout on the front of the cam gears, to to see the rear timing marks on the gears you need to remove the covers

The car would run off it the cam timing was incorrect, but it would not change from bad to good and then worse, it would always be the same. I am betting you have some sort of electrical problem. Start by using this guide to cleaning all your grounds and also clean up the 14 pin connector as Merlin suggested (it is under the little plastic cover on the passenger side fender). After that you have a baseline to start chasing other stuff if it doesn`t fix it.

I also learned everything about this car by itself bereaking down despite of 1000's of euros spend by the previous owner...

The relays and fuses are down at the footwell at the passenger side. It's behind a hinged piece of wood. The first time I saw it, I couldn't believe Porsche would use wood in it's cars. I thought only some English car manufacturer used it;-)

The 14 pin connection: I think the big plug under the hood against the right fender is meant. There is a small black plastic cap, fixed with a big plastic nut. Unscrew this and you will find the plug. Beware of the bolt where the plastic nut is fixed on: it has +12 volts continous.

Oh, I see allready a lot of new comments have been posted, so my story is a little bit out-dated... ;-)

Ok I found the relays,
I did not know everyone meant the relay panel. I have been all though that in the past trying to fix my A/c blower issue, all there is dry and un blemished that I can see?

I have locasted the the hot post on the PS of the car and I will take that apart and clean it all. I looked to see if the black wires to the coils were good and they are not broken or frade in any way, I see a spot on the Rt side of the car front that has 2 wires that appear to be grounds I will clean them as well, and the battery posts.

I just did a visual check so far no cleaning and I started the car and it ran smooth at start up. I do have one question there is a plug that sits on top of the engine that has wires in it that appear to go into the manifold area of the car and it plugs into the harness somehow that plug looks to be taped like the plug itself is missng half of the plug, it has about 5 ot 6 wires I think, and sits close to the oil cap inside of a metal holder does anyone know what that may control?, I am going to have to clean all contacts but I wanted to know if maybe the pluged that looks taped up may be something to do with idle since it looks to go toward the intake area under the manifold with a brown wire hiold ing several wires in it??

Thanks Mrmerlin great description on checking things you are very helpful always.

Thanks again Tony H.

Tony since your posting please add the car info to your profile then it will be displayed every time you post Thanks.
Also the harness you describe is a diagnostic connection for the dealer service so no need to worry about this it should have a cover on it.

Here is a link on how to use the diagnostic connector from Porken
https://rennlist.com/forums/928-foru...ghlight=blinkr

send pictures of the pointers on top of the cam gears. timing could be off a tooth very easily.