Socal_Tom

One or both of my S4 harnesses that plug into the ECUs has an intermittent fault, hoping to get some suggestions on where to source replacement ones or get these repaired. Ideally I'd prefer not to immobilze the car for more than a week or so.

Thanks and happy Friday.

dr bob

I know that SeanR has been supplying them, but don't know if he offers a repair service. Greg has been doing some harnesses but I'm not sure which he has beyond the main front-of-engine KS-2. IIRC you have a 1989 engine in your car now, and transplanted the whole engine management package with it. The injection harness is different starting with 1989 because of the ignition protection circuitry and relay. Make sure the one you buy replaces the one you have.

Socal_Tom

Hi Doc - hope you are all doing well and staying safe.

I have an '88 engine and engine electronics, will double check before ordering anything, thanks for the heads-up.

GregBBRD

Tom:
I've done several, but my current work load would prevent me from taking this on.

If I needed one of these, today, I'd contact Kroon and see if they are making the injection harnesses. They are quickly becoming the "go to" people for wiring harnesses.

Socal_Tom

Thanks Greg (And Mark)

GregBBRD

I forgot to address your existing loom issue.
The odds of finding an intermittent broken wire or frayed wire seem fairly low.
That being said, if the problem is the same with either of your existing looms, the odds of both looms having the same exact wire fault is also very low.

Socal_Tom

Thanks Greg.

Those new wiring looms are 2.390,00 €! Gulp.

I was planing on trying to determine which of them was bad under the same "unlikely to be both" theory. Will dig into it and see what I can find.

Hope everyone has a good weekend when that finally rolls around.

GregBBRD

That seems expensive, but as I recall, they were expensive when Porsche had them.
I got "sucked" into doing some extensive work on two different 951's, which we are currently working on, in the shop. I've got news for the "928" people....Porsceh is "giving parts away" for 928's versus what they are charging for 951 parts. I'm hard to shock, having worked on Porsches for over 50 years, but I'm stunned by some of the 951 part prices.


For you.....There's a pretty basic assumption we make when tracing things....if two separate parts have the the exact same problem....you better think hard about that being the issue.

khalloudy

Kroon can replicate a harness if you send them the original (for items not on their stock list)

FredR

Tom,

How did you come to understand you had an intermittent problem with the loom? Not saying that is not the case but if you can share your diagnostic analysis and how you concluded such that might help us suggest possible workarounds for you.

What I can say from experience is that when it comes to the harness wiring loom the vulnerable part that perhaps is most likely to create a hesitation type problem is the final section of the sub harness to the MAF. I had to r/r mine some years ago. When I pulled the boot back from the plug it was something of a dog's dinner- insulation falling to pieces etc. When I opened the heat shrink back to the main run of the loom the cores were still in excellent condition. Although a bit hesitant, I bit the bullet and castrated that final section along a length of about 8 inches back to where it entered the main body of the loom. Removing the pins from the plug is easy- I used a safety pin to depress the locking tab and out they came. I fitted new cables to the pins and bullet crimp connectors to splice the cables back to the loom- I did not have the correct cable colours but so what? Tidied the thing up with insulation tape and then added some self vulcanising tape over the top. The entire job start to finish took me no more than a couple of hours and I do not work fast!

Not saying that is your problem but I reckon given no other info available for the sake of no bucks and a couple of hours work it might be worth trying that appraoch to see if it eliminates the problem. A new connector/boot from the likes of Roger is also a good bet. I dare say there are other critical connectors but that one in my opinion is the most likely source of such an issue. This r/r cured the mystery transient hesitation my motor exhibited at the time.

The other possible "achilles' heels" were the pig tails to the fuel injectors - I replaced about three of mine whilst I was at it that looked a bit suspect. Problems within the loom and the cabin end terminals are of course possible but a way less likely I would suggest. Other folks may also have "personal favourites" they can advise you about.

SeanR

I just repair them as needed. Kroons the way to go for a new ECU engine harness, he's got all the right stuff to do them.

Socal_Tom

Thanks for the responses. This is a ‘84 with an ‘88 S4 engine and wiring and dual ECU set up. Basically OEM S4 running gear to keep it standard.

@FredR - I have another thread on this but the car runs great (bit of a beast actually) with the harness and ecu laying on the passenger floor but when I try to install it where it tucks away I the car won’t pull above 2500 and/or breaks up under acceleration.

i had a friend drive while I manipulated the ECU harnesses and I was able to occasionally reproduce the fault, so I believe I found the harness needing attention.

@SeanR - send you a PM

Thanks and hope everyone had a good weekend.

dr bob

If it wasn't for matching all those annoying color codes on the individual wires, making a new harness would be pretty darn simple. Find some kynar-insulated tinned conductor cables, and this time put in some intermediate connectors, firesleeve and high-temp heat-shrink... Could probably offer them for around $1k tested.

Maybe the most important thing will be building a test fixture that verifies correct connections, tests for shorts between conductors, etc. Would be way handy to have one that could be used for harnesses still in the car. Build one that looks like LHx and EZx brains, with a centipede harness to loop out the passenger door and plug into the individual connectors under the hood. Whole thing runs on a raspberry pi controller with a USB battery pack and a Kindle Fire tablet connected by wifi. The test/diagnostic tool would be at least as handy as a new harness. Plugging each engine-bay connector in would be a huge diagnostic step too, as you'd be forced to replace all those crumbling connectors and frayed wires just to get the thing plugged in.

Maybe do the harnesses in all gray, like the CE panel?

soontobered84

Dr. Bob,
You can be so funny sometimes! LMAO

Kevin in Atlanta

If you know the general area couldn't you cut harness where it bends to look at the wire?