Wiring harness did the trick!

[RPB81]

Just wanted to first say thanks for the input from everyone in trying to assist with my rough idle issue! After replacing caps, rotors, coils, and fuel pumps... I finally got under the hood myself to find that indeed the harness was deteriorating. Ordered one from parts.com for $570 total and made my dealership install it under goodwill for overlooking this harness on numerous visits.

Suffice it to say the car now purrs, I forgot how smooth it used to be and am still kicking myself for being lazy and relying on the dealership to figure my prob out! After the new harness was installed I really cut into the old and could not believe the car would even turn over/drive in the state it was in, fuel injector inputs were in terrible shape!! I look at all the other parts I threw at it as common maintenance, new set of Bosch fuel pumps cannot hurt either Still wondering if the idle/surging fried my EZL or if this was unrelated, my baby is running like a cherry though so no complaints here. Now understand why the winter weather exasperated the problem as wires were exposed and probably freezing overnight to make for a pretty rough start to say the least before warmed up.

Thx again guys, great site!!

 

[JordiC]

Great news and congrats! Getting the dealer to waive the labor is even better.

 

[gerryvz]

Indeed new fuel pumps are always a good idea if the car has more than 100K on it. I just replaced the pumps on my 560SEC (which uses the identical pumps as the E500E) and they lasted 130K (replaced last in 1996). Unfortunately, the ethanol-laden gas that we are being forced to put into our cars (they say "up to 10% ethanol") these days is slowly ruining our pumps, hoses and fuel systems.

Really glad that you solved your problem. More than a few owners have solved their problems over the years with a new harness. If you haven't replaced your harness yet, you're living on borrowed time more and more as each day ticks by !!

BTW if you took photos of your harness and the cracked insulation etc. please post them, starting a new thread on the topic. I'd like to have a thread dedicated to degraded harnesses and their photos/symptoms.

Cheers,
Gerry

 

[RPB81]

Indeed new fuel pumps are always a good idea if the car has more than 100K on it. I just replaced the pumps on my 560SEC (which uses the identical pumps as the E500E) and they lasted 130K (replaced last in 1996). Unfortunately, the ethanol-laden gas that we are being forced to put into our cars (they say "up to 10% ethanol") these days is slowly ruining our pumps, hoses and fuel systems.

Really glad that you solved your problem. More than a few owners have solved their problems over the years with a new harness. If you haven't replaced your harness yet, you're living on borrowed time more and more as each day ticks by !!

BTW if you took photos of your harness and the cracked insulation etc. please post them, starting a new thread on the topic. I'd like to have a thread dedicated to degraded harnesses and their photos/symptoms.

Cheers,
Gerry

Will do, thx again!

 

[Cadence]

Great that it is running 100% again.

What was the part # for the harness that you replaced? I believe there is an upper and a lower...

My local dealer quote me $3XXX for the engine harness but I know they aren't looking up the correct part #s!

 

[gerryvz]

There are two different upper harnesses depending on the year of your car ... early and late. The part numbers are documented in another thread here.

Cheers,
Gerry

 

[J-Sauce]

Glad to hear it did the trick. I should have taken photos of the lower harness I pulled out a couple months ago. I would be happy to contribute to that thread with symptoms of a failing lower harness Uncle G!

 

[RPB81]

Glad to hear it did the trick. I should have taken photos of the lower harness I pulled out a couple months ago. I would be happy to contribute to that thread with symptoms of a failing lower harness Uncle G!

What symptoms were you experiencing from the lower harness and mileage on car please? I have been told that its typically the upper harness that deteriorates due to heat, so I am interested to get some feedback on what to expect from the lower one?

Thx!

 

[gsxr]

What symptoms were you experiencing from the lower harness and mileage on car please? I have been told that its typically the upper harness that deteriorates due to heat, so I am interested to get some feedback on what to expect from the lower one?

The lower harness connects to the starter, alternator, oil pressure sensor, and oil level sensor.

There are often no symptoms at all, but when the insulation starts coming off the lower harness, there is risk of short-circuit and possibly damaging something. It won't affect engine operation though, like the upper harness (the upper harness connects to all 8 fuel injectors, the cam advance system, and all temp sensors - which has a huge effect on engine performance!).

The price has gotten silly on this, current MSRP in USA is $294 USD. Crazy...

I replaced mine before it caused any problems:

New harness: