Good Evening Everyone,
I have been reading this forum for many years. I have a 1985 928 that I have owned since 2004
it is Silver Rose Metallic, has sport seats, X pipe ,Porken Chips tensioner and torque rings
this is just a short list of what has been done since my acquiring my 928.

I have an issue I cant figure out.
Last winter I changed the timing belt and installed the Porken tensioner
and installed Porkens computer chips.
From that point forward the car has not run consistantly
What it does cuts off like one has turned off the igintion
When it does it cuts out after approximately 20 miles of driving prior to that she runs wonderful
What has been done
New battery, all grounds cleaned, all 14 pin connectors cleaned, battery positive cable cleaned , new ground strap, new cps, new temp 2 sensor, new 53 relays for EZF LH and fuel pump, new iginition switch
anyones thoughts to solve David

 

I have a 1987 928 S4 and it does the same thing, starts fine, it runs good for about 10 to 15 minutes, as soon as the temp gage is up to normal, and exactly as the electric fan kicks on, the fuel pump relay clicks and the car dies. I also put a new CPS in last week, thinking that was the problem. Appreciate it if anyone can point out a probable cause. Thanks

 

David to test this drive the car till it stalls,
then replace the fuel pump fuse if it works,
then I would suggest to look at the connection points where the wires connect to the rear of the CE panel for the FP,

you want to see if power is flowing out of both wires,
if this connection is corroded then the FP fuse will be getting hot thus alerting you to the fact that there is corrosion in the connection.

An IR gun may also come in handy to shoot the other relays and fuses to see if any of them are hotter than the rest,
if so same thing is happening to the relays.

 

Airman I would suggest to clean the battery terminals,
also remove the 2 red wires attached to the Positive terminal and clean these.

Clean the ground strap connection at the chassis, inspect your strap for corrosion in the ground strap.
If any doubt then replace the strap, Roger has new ground straps

Also clean all of the fuses and the relays and the grounds above the CE panel,
and the red wire connections to the top of the CE panel.

Clean the 14 pin connector at the hot post junction

 

appreciate your advise very much "Mrmerlin", is the ground strap the one by the battery in the trunk? where is the 14 pin connector?

 

Add: I added a second pic to hopefully be clearer. The jump post and cover are labeled #1.

 

Craig care to post your ground strap picture

 

Sure Stan.

Airman, as you can see in the first pic the strap looks 'normal'.
Dissect it, and it is not looking so well. Degradation will commonly occur at the battery end if the battery is not vented. The acidic vapors will do this to a copper cable. You may see normal voltage (energy potential), but you will not carry amperage (current) optimally. This can wreak havoc with many systems.

 

Thanks Craig, great picture.

FWIW on Craig s picture, the other end of the strap can also corrode ,
so the same kind of damage can start at either end of the strap

 

Ken posted recently about the fragility of the solder joints in the mounting of chip-holding sockets within the brains.

 

Thanks everyone I appreciate all the info very much, the 928 is new to me as you can tell. I noticed my battery gage on the dash jumps every few seconds, would that be related? I will try to get some of the inspections/repairs done this week.

 

Question and Clarification:
My 928 didnt do this prior to last winters updates with Chips and timing belt refresh.The symptom. Car starts and idles wonderful. Runs for about 20 miles then the engine cuts out just as if I shut off the key.
The car will immedaitely restart. I have restarted it while still on the move by jiggling the key (that is how I jumped to the igintion switch orginally as the fualt.). MrMerlin does your rec require remove of the CE board ? yep I think I fixed it till I broke it!

 

DFW56,

I'm having a similar problem with my 86.5 that started after installing the latest version of the chips, 4.1 I think. After reading your post, I think I'll email Ken in case he doesn't see this thread, and let him know in case he has heard this feedback from other customers. In my case, the engine occasionally dies at red lights, but sometimes it just sortof misses randomly at idle. I also sometimes get 3 flashes of the "!" on the dash.

 

Well, that information is somewhat helpful. Do everything Stan said in post 4 and get a new ignition switch.

 

All V4 chips are 4.2 - V4 began shipping 09/2012.

Your case sounds like the CO and/or idle speed needs adjusting.

Turn the idle screw CCW one turn at a time until the idle recovers nicely.

Check the MAF CO screw is not too far ± from 382 ohms.