Porsche Enthusiasts Club Forum

Morning Ladies and Gents,

Rebuild finished, running like a trooper, for a week..
she's now exhibiting some of those wonderful wonderful electrical issues which i grew so fond of..

Symptoms:
random misfire/stutters on light accelleration
revs fluctuation (sometimes) whilst sitting still
if she is feeling particularly naughty, she cuts out when turning on various eletrical items, e.g flashing full beams, windscreen blower or sometimes just whilst holding constant speed.
The entire ignition cuts and restarts within around 0.5 seconds.

Suspect:
Old alarm system sitting in the bay, i removed the sounder as it is not working and i do not have the fob, as a result there is a bit of wiring laying about that i'm not sure what to do with.
Earth wires by the headlights
Dashboard earth wires

So far, i've replaced and cleaned the ground fr the battery and on the back of the engine, i also replaced the battery with the king of all batteries and replaced the DME relay with a new one.
I've also bought a compression tester to check that the random misfires aren't caused by my minorly worn #2

Help me?

I feel your pain. I am also suffering from the random stutter issue. It doesn't cut out though.

I have had the throttle body cleaned and injectors ASNU cleaned and this did no good. I have cleaned the main grounds but can't get the rear engine ground off the bell housing (due to the mass of pipes preventing access) so that remains a mess.

I have swapped DME relays's as well. It's recently had new fuel filters (in-line and in-tank) and a new fuel pump. It's also had new spark plugs and new battery.

My next tack is a new coil and new distributer, rotor arm and HT leads.

If that doesn't work I've run out of ideas bar a new DME.

So far the list of things i've done includes the relay, battery, new grounds, injectors ansu cleaned, new TB, new (used) fuel rail, vacuum hoses replaced with silicone, rotor and cap also replaced with new sparks.

coil, leads and dme on top of the other bits are the only possibilities for me i guess, keep me posted if you find yours!

Water in your fuel??

I can remember a certain fuel station that I commonly used (Guildford way) and these symptoms would occur each time. I then used another station by chance and all then was fine...

Not sure if that helps...

Dave
CT

Have you checked your alternator? You should be measuring about 13 - 14 V across battery with the engine running. When my alternator was faulty my car would run rough when lights etc were turned on.

I let the MOT guys check my alternator and they suggested it was fine, however I don't trust anyone with my car so I will check that tonight,

unfortunately this issue happens no matter where I get my fuel.

I sat by the exhaust last night, I would liken it to when you put your hand over the end of something and then let it go, along with a little pop sound. the sound isn't rhythmic but is regular. I could only think it would be down to combustion issues. (compression tester should arrive tonight and i'm also retensioning my belts so will report back with findings from comp test.)

My alternator is reading 13v on the dash.

I've got my fuel from BP (Ultimate) and Esso and it still happens.

The tank was completely drained when I got the in tank filter changed.

Would re-tensioning the belts have an effect on this?

try changing the crankshaft sensors - might one of them is playing up? There is also a ground connection under the fuse box that might want looking at if other electrical items are causing interference.

Compression is 190~ on each cylinder what a relief!

now i can start hunting through the cheaper bits! (didn't want to go through that lot and find out it's due to my scored #2)

going to properly check my timing and make sure when i put her back together i haven't set it extremely retarded or advanced causing pre ignition

my dash volt guage doesn't work, i don't trust any reading on there except the tacho and oil pressure guage, as for the crank sensor, i only have one as it is the S and afaik it's more of an on/off thing?

Tonight i will check there is no puddle under my dme and that the fuel quality switch isn't set to farmer oil residue..

I'll also check that the fuse box is all good underneath.

Dodgy ignition switch. Have a pull, clean & reseat all the fuses & relays as well.

Do you mean the ignition barrel of the ignition switch unit?

Having just rekeyed my new passenger lock to the ignition key and driver door key I hope it isn't the ignition barrel.

think the switch part is seperate

So i had a poke around to no avail
i'll see if i can catch it on video to show you guys, oil pressure has started doing thing it used to do where it flickers around a bit on idle.

with my compression being almost perfect, no loss in oil or coolant, guess my next port is to test fuel pressure? to do this do i just plug a guage into the rail? will this tell me if the damper/ fprv are working correctly?

i can't see this being a vacuum issue as all my hoses are new.. my dipstick tube did pull out the other day though.. i tapped it back in with a hammer (gently) don't suppose a minor vacuum leak there would cause any issues?