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2007 911 GT3 RS, 1990 420SEL, 2007 S550, 1994 SL500 6.0, 2011 Aston Martin DBS
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Discussion Starter #1
My 1994 is just full of problems that come and go and this is one is one I can no longer stand. So I'm going to pull the engine wiring harness and replace it, unless someone here tells me other wise.

1. Random misfiring, some days it will run so smooth you cannot tell its running. Other days you will feel and hear the misfires and some days it stalls out even.

2. Backfire, some times going up a hill or anywhere situation where there is a load on the engine, the car will misfire then you will hear a loud bang and flames will shoot from the exhaust. (yes this looks amazing, but I hate it)

3. Hesitation, under throttle you can feel the car getting to a certain rpm, bouncing off the certain point of the rpms before continuing on.

I'm also going to throw out the Bosch Platinum 2+'s, and replace them with either the F-7/F-8 DCO spark plugs.

WDB1290671F104815 is my VIN and I'd like to know which harnesses I need to change on my motor. Its a 1994 Euro-Spec if that helps.....
 

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1998 SL500
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12 Posts
Wow, it sure sounds like you have a timing issue, but not sure I'd replace the engine wiring harness first to try to solve it. You probably have a plug or coil pack issue, or maybe a timing chain is slipping. Plugs can be changed (if bad) and coils can be tested and replaced if out of spec. Chain is hard to test without pulling things apart. But, I would go after the misfires as a timing/firing issue before a harness replacement.
 

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2007 911 GT3 RS, 1990 420SEL, 2007 S550, 1994 SL500 6.0, 2011 Aston Martin DBS
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522 Posts
Discussion Starter #3
My coils and timing have all been inspected and are all flawless. When I cut some of the harness insulation I looked and it disintegrated when i touched it. I taped it back with electrical tape and stopped touching it until I can figure out what I should do for a replacement.

The idle on the motor when its not misfiring is so smooth that I can balance coins on the block
 

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Greek God of the R129
SL500-500SEL-190E
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8,389 Posts
Check codes, plugs.

Remove and read them, get the F.... type. Haha.

If F.... plugs fix the problem you can stop here.

If not keep going.

Caps.

Rotors.

Rotor adapters make sure that you have the new kind.

Stop.

Or keep going.

02 sensor, ck for also sensor wires touching the drive shaft.
autohauseaz $95 or I got a universal for $35 need to cut wires. ;)

How many miles on the clock?

Stop.

Or keep going.

Ign. wires.

Ign. coils

Crank sensor.

Vacuum leaks.

I am not saying replace all these parts, just check them out, good/bad.

Flames damage the converters.... $$$$

Regards,
aam.
 

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If your wiring harness is crumbling in your hands there's no point in doing anything until you replace it. It's a 129 540 77 05, fortunately a U.S. part, around $600 at parts.com. Check the old part number to confirm.
 

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'97 SL500, 06 Subaru Outback, LL Bean 3.0
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735 Posts
If your wiring harness is crumbling in your hands there's no point in doing anything until you replace it. It's a 129 540 77 05, fortunately a U.S. part, around $600 at parts.com. Check the old part number to confirm.
Absolutely! I'm surprised at the other replies. It's obviously got to be replaced, and it can cause all kinds of problems.
 

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2007 911 GT3 RS, 1990 420SEL, 2007 S550, 1994 SL500 6.0, 2011 Aston Martin DBS
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Discussion Starter #7
Absolutely! I'm surprised at the other replies. It's obviously got to be replaced, and it can cause all kinds of problems.
Where on the harness will I find the part number?
 

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2007 911 GT3 RS, 1990 420SEL, 2007 S550, 1994 SL500 6.0, 2011 Aston Martin DBS
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Discussion Starter #8
Where abouts on the harness will I find a part number so I can confirm?
 

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Sith Lord
72 280SE 88 560SEC 92 E500 6.0 95 SL320 14 GLK350
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Never underestimate the power of the Albert side of the force.
 

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Premium Member
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9,274 Posts
Where on the harness will I find the part number?
I just got finished in a thread "cheap wire harness- where are they" something like that and "M119 ETA throttle body, MAF problems" which mentions the wire harness problems. Actually I'm not finished there yet. I'm afraid my bad wiring could have fried some stuff in the ETA, MAF or main computer. I'm not sure yet. Still I wish I would have replaced the harness earlier. Parts.com ended up being the cheapest and it was an OEM straight from Mercedes Benz distribution center in Illinois. I would carefully read info in those threads and Lynns advice on buying from parts.com . They were the cheapest and the deal went pretty well. The only cheaper source I could imagine is if you find a one time thing on ebay. You are going to also need to repair or replace the 11 wire cable going to the ETA unless it has been done already. It may even be worse than the engine harness. I could not find that part but I did not look very hard either. I just repaired mine. If you peel back the ETA cable or the engine harness and see bare wires I would suggest never turning the key on and disconnecting the battery until it is repaired. Odds are you twisted and wiggled the cables enough to make bare wires touch in places you have not uncovered. Your harness , I am almost certain is exactly the same as mine 129 540 77 05 . Do not confuse part numbers for terminal ends and the plastic peice that runs with the fuel rail. They all come with the harness. I think my harmess number was on the large main "lever plug." It is there on the new one as well as on a tag by the end of the harness by the temperature sensor terminals.
 

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'93 SL500 (sold), '88 GMC Sierra 360,000 miles, '86 Yamaha FJ1200 (criminally fast)
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770 Posts
My indy mechanic says, it is possible to damage the computer module or modules, due to a defective ETA / harness wiring or an elec glitch in those parts.

The hassle is finding out which part also got messed up, or if they. So many parts are interconnected.

But all this firing 'miss' and backfiring..... sounds like a sparkplug wire is crossed. Or sparkplug wire is arching or connection inside the wire boot. (as a place to look, before digging in too deep)

But nothing can be solved if the wire harness is crap.
 

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'97 SL500, 06 Subaru Outback, LL Bean 3.0
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735 Posts
My indy mechanic says, it is possible to damage the computer module or modules, due to a defective ETA / harness wiring or an elec glitch in those parts.

The hassle is finding out which part also got messed up, or if they. So many parts are interconnected.

But all this firing 'miss' and backfiring..... sounds like a sparkplug wire is crossed. Or sparkplug wire is arching or connection inside the wire boot. (as a place to look, before digging in too deep)

But nothing can be solved if the wire harness is crap.
You must start with the wiring harness. Maybe other stuff next, maybe not (or not near so many).
 

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2007 911 GT3 RS, 1990 420SEL, 2007 S550, 1994 SL500 6.0, 2011 Aston Martin DBS
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Discussion Starter #13
Alright so here's what Ive accomplished so far,

I went on the hunt for the correct F-7 DCO plug carrying the part number from A 003 159 16 03 from the dealer in Munich. However it looks like no dealer here even can find this part number? And nobody in town seems to have this plug, so I had to pick up the FR8DC+ which is a replacement for the F-8DCO instead which looks like it should be a better replacement than the Platinum 2+'s in it which have doubled resistance of the spark.

Me and my dealer parts guy searched by VIN number and it comes up at a 129 540 77 05 for the harness. He also then immediately informed me that this part is 1,200 dollars....
 

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'97 SL500, 06 Subaru Outback, LL Bean 3.0
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735 Posts
At parts.com its $604
"Me and my dealer parts guy searched by VIN number and it comes up at a 129 540 77 05 for the harness. He also then immediately informed me that this part is 1,200 dollars....""

Go for one or the other. $604 or $1200 it's the only way that money makes haapiness. :thumbsup:
 

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2007 911 GT3 RS, 1990 420SEL, 2007 S550, 1994 SL500 6.0, 2011 Aston Martin DBS
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Discussion Starter #16
"Me and my dealer parts guy searched by VIN number and it comes up at a 129 540 77 05 for the harness. He also then immediately informed me that this part is 1,200 dollars....""

Go for one or the other. $604 or $1200 it's the only way that money makes haapiness. :thumbsup:
I'm a student, so paying 604 for a wiring harness doesn't make any sense to me anymore..68 hours of work to pay for this thing..

Parts.com doesnt ship outside the USA, I'm trying right now to order the part and its not letting me :(
 

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I'm a student, so paying 604 for a wiring harness doesn't make any sense to me anymore..68 hours of work to pay for this thing..
(
No comprende. What does make sense? Scraping the car would seem to be the only alternative to fixing it.

Actually at that ratio you might be able to justify rebuilding the harness.
 

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2007 911 GT3 RS, 1990 420SEL, 2007 S550, 1994 SL500 6.0, 2011 Aston Martin DBS
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Discussion Starter #20
No comprende. What does make sense? Scraping the car would seem to be the only alternative to fixing it.

Actually at that ratio you might be able to justify rebuilding the harness.
Right now I'm seriously considering selling it to move onto another R129, the costs this car has is really starting to run me broke.

Can anyone in this forum shed light on howto get a 604 dollar parts.com harness in Canada? As they wont ship to me.?.
 
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