$513 Wire Harness? $700 Idle Control Box? Whoa, Nelly!

Rough idle, no start w/o gas pedal on 93 300E 2.8 with 107k leads me to buy a new OVP. Helps the warm starts, but still idles rough. The car sits in my garage for 30 days while I try to sell it. The wife wants a wagon. After a 30 days hiatus, I start it up to take it to a potential buyer, and it won't restart for the buyer after it's warm. Starts for me, but now the buyer's spooked and he walks. Okay, time for a real tech to take a look.

My all-MBZ tech and his indie shop tell me that I first need a new wiring harness - he's surprised the car runs as well as it does, with so many shorts, he says. He can't even diagnose anything else until it's in. Okay, $513 harness plus diagnose and installation (plus a new driver's door stop, to bring the "crack - crack" back to a satisfying and subtle "thunk - thunk" as the door swings open) brings me up to $680. I'm cringing, but not yet in pain.

Now, the zoinker. I call him this a.m. and he tells me the car now starts fine, but still idles a little rough, and from time to time, can stall under the right conditions. The car's driveable, but he recommends an "Idle Control Box," his exact words. He says it costs $700 new, that no units are 'reconditioned,' but that installation will be a snap (so THAT part won't cost much). I'll be lucky to get out of the door under $1500 when it's all over.

NOW I am in pain.

1.) Do those puppies actually cost $700? And there are no reconditioned units available?

2.) Should I just try to sell as-is, with a slightly rough idle, for $12k firm, or should I suck it up, put the new idle unit in, and sell for $12.7k? (or should I get a new valuation tool?)

Any advice would be much appreciated.

I don't know about yours but the Idle Speed control module cost me $230. I changed it myself. It didn't cure my problem. Had to replace the Ignition Control Unit (ICU). Replace it yourself and save a ton of money but be sure the tech tested it so you don't play musical parts (like I did). Or, sell as-is and refer them to your mechanic. Good luck!

Steve
'85 500SL Euro

[jimSF]

Mercedes extended the warranty on Wire Harnesses to 125,000 miles. If you haven't done the repair, you might save $512 by taking it to a dealer.-jim

[JayGH]

Hey Jim SF, my dad has a 1995 e320 as one of his cars. He took his car to a non-dealer shop. They do better work than the dealer....but they chargedc him for 500 bucks for the wire harness......his car has only 60 k on it....have any written proof of this 125 k mile warr.???

Ryan,

Confirm with your mechanic what the specific name and part number of the module is that he is recommending you replace. From your symptoms, I wouldn't be surprised if the part is the EA/CC/ISC module (Electronic acceleration, cruise control, idle speed control).

This unit retails for about $788.00. We have seen several of these units fail on M104 Motor cars with a little over 100,000 miles. They somtimes fail in conjunction with the throttle slide, another extremely exprensive part, which fails because of faulty wiring--just like the engine harnesses. We have started to jokingly refer to replacement of these three components as the "supplementary 90,000 mile service."

If your vehicle has been dealer serviced from new, you may get somewhere with Mercedes-Benz in terms of reimbursement for the engine harness. We have not had much success with our three local dealers if vehicles have not been dealer serviced, but it is always worth a try.

Good luck to you, and please let me know the part number of the unit which your mechanic is recommending you replace.

[jimSF]

Jay...
I agree with the last post. Try to approach a dealer and see if the service bulletin on the harness covers your engine - then try to get a reimbursement or something. My mechanic verified that MB extended the warranty on wire harnesses to 125K miles, but are obviously not spreading the word. Understandably so!
jim

[Benzmac]

And here is the biggy!

I have sent 50 or more wiring harnesses to the dealer with under 120K and all were done for FREE! (RBM of Atlanta)

Also, I have replaced several of the throttle actuators and all have repaired the bad idle/ stalling complaints. I have NEVER had to replace the control unit! I could see this ONLY if the throttle actuator is faulty and it BLEW out the controller. So if you replace the controller without the actuator, well it will blow too.

Have your mechanic GENTLY slice open the throttle actuator harness and look for broken wires. I'd start there.

So I call for an update on my car today, and the mechanic tells me that the "Idle Control Box" didn't really help the problem like he thought it would. The poor guy has now gone through every circuit on the car to figure out what it is. He now suspects it's the fuel injection computer (didn't give an official name, just that description). He says it's the last thing left. He tells me that when I take a look at this wiring harness that was replaced, it's little wonder that it may have burned out the FI computer.

So the good news is that he's pulled the $700 Idle Control Box out of my car, and he won't be charging me for it.

The possible bad news is that a USED FI comp for the 2.8 engine is roughly $700, and a NEW unit is $1500. I'm told the FI comps for the 2.8 are somewhat rare, and unique to the 2.8, so you can't swap them for, say, a 3.2 FI comp. He's got another 2.8 coming into the shop today, so he's gonna grab the box out of that one and see if it helps. He's a nice guy, apologized about keeping my car so long, says he usually moves cars out the same afternoon that they're worked on, but this one's got him stumped.

In other news, I asked the tech about the wiring harness for my 93. He tells me that, yes, MB was replacing these, but only back to a certain year. He says at this point, they wouldn't cover the 93, he thought they might still be covering the 95's. ???

So, I'll have to wait and see about the FI comp. He made it sound like there weren't any other options after that...

How does the price sound for the 2.8 FI comp?

Is he correct in the range of years covered for the wiring harness, vs. just straight mileage?

Thanks again for any input. You've all been a real help.

[Benzmac]

Did you not catch the ideas presented? I don't think you are having a problem with the fuel injection computer.... You need to have him look at the throttle acutator!!!!!!!!!!!!!


It wil cause weird problems.!!!!

[Kebowers]

I have seen several 'faulty' electronic throttle actuators. What failed was the insulation on the wiring in the cable between the actuator and main harness. The insulation just crumbles to dust and any movement eventually causes 'electrical leaks' that usually send the car into the 'limp in ' mode. The EGAS computer constantly checks the voltage of the positioner variable resistor and the reference variable resistor, If they don't match it goes 'TILT' because it means the actual position of the throttle valve is not what the computer told it to be.

The root cause is faulty wire insulation!! Ford got hit with a very large lawsuit bill for a less expensive flaw they ignored. Maybe MBZ is next?

I may be experiencing a similar problem with a 94 E420. It started hesitating while driving at highway speeds; and idle would hunt up and down. Computer indicated a fuel injection or open circuit fault. MB tested fuel injection and said it was OK; they then wanted to replace the wiring harness (approx $1300; 7 hours labor @ $100). An independent shop thought the harness was in good shape and replaced plugs, dist caps and rotors. It seemed to run better but continues to record same code immediately at ignition after reset and idles slightly rough at certain times.

Car has 90,000 miles. Has anyone seen this problem; does the E420 have the same throttle actuator?

[Benzmac]

I have seen the wiring fail, the throttle actuators fail, and the air mass meters fail. Any of the 3 will cause this code.

If it is a code 19 in the DM, you can e-mail me and I will tell you of a fix.

Is my MB shop taking me for a ride $$$ ? Help...
I have an 86 300E. She ran like a baby until last week. She suddenly felt as if she were losing power. After I restarted her she sounded like a U-Boat almost like a diesel and ran really rough. A day later a attempted to crank her up but she would not catch I had her towed to a highly recommed MB shop who informed me that it was a fuel pump and filter. After the fuel pump was replaced she still runs very ruff and sounds aweful. He then told me that it was an electrical problem ( fuse box or something )and that I had some burnt wires. This just dosn't quite sit right with me. I'm hoping it's not the case but I'm thinking valve or piston. What's you take?

1. Loss of power
2. Loud knocking
3. Would not start < strong crank >
4. New fuel pump and filters
5. Constant knocking - Rough

Need your help. What do you think?

[engatwork]

Do a search in here on the OVP Trey. That may be your problem.

Sorry, Maybe a stupid question. What do mean by OVP?