AlecJK

Hello:

I have a 2005 ML350 Special Edition. Has 160k miles. It is a vehicle that I use at my vacation home, so it does not get driven a lot......When it rains, it pours....two issues:

Problem 1: Out of the blue, began idling rough at stoplights. (I slip into neutral to minimize the shake) At speed she runs and accelerates like a champ. Throws no codes. I had diagnostic done on the Sentry system, still no codes. Mechanic speculated a drive shaft sensor and replaced it. Runs bit better but not much. I have sprayed the MAF with cleaner and have run good gas additive. Had spark plugs changed 3000k miles ago. Still shaking at stoplights. Any thoughts?

Problem 2: During a rain storm, my passenger side got flooded due to a clogged sunroof drain (passenger A pillar). When I came down, water was sloshing underneath the floorboards. Pulled the plugs on the forward and aft rockers and emptied the water and dried it out. Then shortly thereafter, my both rear windows stopped working from all switches. Checked the 25A fuses for rear windows in the passenger footwell. Put circuit tester on both sides to the fuse and the light came on. (plus the ext mirrors work which is on the same circuit) Pulled the fuse capsule out of the SAM and no corrosion but still sprayed with electric cleaner. They were working fine before the rain. Any ideas? There is a green module on the fuse box windows circuit with of all things a GM stamp? I am going to replace to see if that is the fix.

As we all know there comes a time when you have to stop throwing $ and an oldie. She is a great vehicle for my uses and I'd love to keep her.

Any thoughts/ideas on a fix of either issues would be greatly appreciated!

Many thanks in advance!

Al

Jerry Easley

Couple of comments to start:

Are you DIY for simple stuff, or off to the mechanic for everything?

1. Is the rough idle immediate on starting while still in cold loop, or after it has warmed up and in closed loop mode? You can check this by doing a cold start and letting the engine warm, thermostat open watching the temp gauge to note if the 'running rough' sets in, and at what temperature.
Or, disconnect the MassAirflowSensor and drive around for 10 minutes (no harm to the engine, just not meeting emission requirements). This forces open loop and will prove spark, fuel delivery and timing.
If the rough idle is not present with MAF disconnected, then your problem is in the sensor systems. If the rough idle is present, look to basics.

2. You describe this as a seldom used and long-stored vehicle. If the rough idle is present only when in closed loop, please first check all vacuum hoses or leaks - poor fit, cracks, etc using the underhood diagram on the Emissions control system. Start with the MAP (easy, right at the front of the engine) and do the all others as well including the brake booster hose and it's connection at the manifold. There is a good chance with the age and the inactivity of the vehicle that one of these has dried out and is now leaking. If this ML was my vacation house vehicle, I would replace them all for PM reasons. Less than $25 and 30 minutes. Those on the EGR valve are often not failed and are a little more difficult to replace, but are still DIY doable with a simple set of curved-head forceps;

Hint: These are mm-sized hoses, not inch-fractions like at O'Reilleys. MB sells the hoses very cheap, including the molded ones. Some are in lengths of 1 foot. Still cheap. Drop into the local MB dealer for a piece, or go to classicparts.mbusa.com. This official MB department is in Long Beach and is a great resource for older MBs like ours.

2. I had a similar problem on my '01 ML320 Sport, stored in CA for my trips there. Intermittent use. Traced it to a leaking vacuum hose on the MAP (Manifold Absolute Pressure) - 10 min fix. Later, I also replaced the seal at the intake end of the Brake Booster hose - you need a mirror and a pick, otherwise easy. Reply if you need tips.

3. If it is a closed-loop problem It can also be the Coolant Temp Sensor - watch your on-dash gauge to see if it is indicating temps as expected.

3. If your vaca-home is near an O'Reillys, go there and use their scan device. All systemwide are now Innova 530's. It has a lot of basic functions, including a very useful and accurate Battery and Alternator testing mode (counter people often don't know this - it is in other tests on the menu - center button on right side if I recall correctly - google it). Check both bat and alt while at it since this vehicle is in intermittent use and has lot'sa miles. Low voltage at low RPM caused by aging voltage regulator will cause mis-fires. Most likely the voltage regulator can be replaced. Is cheap and easy and keeps the Bosch alternator in use. The alternator itself is good for over 200k most likely.

("I slip into neutral to minimize the shake") Do you as well advance RPM's? if "Yes" and the rough idle smooths out, then back to vacuum leaks or seriously consider it might also be a low rpm/low voltage on old alternator/aged battery. I do not buy AGM battery replacements typically as it is not useful, but that might be a good choice as your vehicle shares the same use characteristics as a marine vehicle. Short use periods followed by long storage.

3. Would that be a "Crankshaft Position Sensor" that the mechanic replaced?

4. Just a hint: When posting "Dead Ends" describes my ex-wife. More eyeballs on your problem (not mine) will be had with more informative title.

5. About the rear windows: Those are not essential functions. But air out the interior - summer is coming - let heat drive off the moisture and see if the problem resolves. If not and it still bothers you, get a wiring diagram, and a multimeter, and find the last common point. Strange that left and right would both fail.

6. I would appreciate the courtesy of a reply/followup. Feel free to PM if you want.

if you can't tell, I am opposed to 'parts-darts' solutions driven by scans showing a 'failed sensor'. I prefer to first do a simple PM Diagnosis. Sensors rarely fail. Wiring (corrosion at connections, bad grounds), hoses, fuel filters,etc do.

And: Provide your VIN and I will look for a wiring diagram or window circuit troubleshooting guide.

Out, here. NOTE: I have 2 ea ML320's which I love - both at 190k on the chassis. Best truck ever.

jay4usc

#1 could be your motor mounts. Those mounts gets hard over time and will cause rough idles at stop lights. I had this problem with my w613 and tried to fix everything except the motor mounts. When they were changed rough idles disappeared

AlecJK

I have done the test for motor mounts by revving the engine and seeing if it heaves to one side. It does not, and visual inspection to the extent possible does not show wear. I will look again.

Thank you for your suggestion...much appreciated.

Al

jay4usc

I did those same test and felt and look perfectly fine. Plus, I rarely drive my 2001 W163 which only has 100,200 miles and replacing the mounts was the last thing in my mind. I ran out of options and it was bugging me so I decided to replace them. The mechanic showed me how visually they look just like the new ones but after holding them, the old ones felt like bricks compared to the new ones. He explained how overtime the mounts just get hardened which is what’s causing the vibrations.

good luck 👍🏻

Dfixit1

As to the motor mounts. My story of woe was with my 95 F150.Not exactly the same animal but motor mount issues share similar components that can fail in very similar ways. On the way to make a "transaction" back during covid I found my truck shaking, at speed, wasn't bad but at "red light" felt like it was about to "Lift Off". Finally got it home and replace the visually obvious mount on the passanger side. The rubber was still in place but the torque would show a seperation and only the Pin holding it all in place. I replaced that mount,, still the same issue. What the heck, replaced the drivers side which was "as bad " as well. Then still in full shake mode I had to get creative in my search. I finally found my harmonic balancer had come apart and the outer portion was moving and not in sync with the motor. I replace the harmonic balancer, then loe and behold,, smooth as a baby's behind slathered in talc.
As to the electrical, my Sweetheart's son has a Mini, not driven lately but I run it once a month and keep on a trickle charger. We live in the mountains surronded by TREES!!!!!!, over time his sunroof drains clogged hence 2+ in of water in the floor passanger side when I had looked in after a more recent RAIN event. After pulling and repairing that, then drying out the floor there was 3 of the little running lights on the fenders stayed on all the time. That took days with used a 6.5 HP wet vac then a big rock pressing a towel down into the carpet to keep wicking that up then a box fan placed in front of the seat to finally get all that mosture out.
Wish you luck with you ride. I just love my 2000 ML ans do all I can to keep her up and running. If you decide to letter go I'll be happy to come pick it up. But seriously,,, hang in there and PEASE let us know what you find is wrong.

croat

Bad motor mounts are easy to figure. Pop the hood, put car in D with left food on brake pedal and then give some gas and other person to check if engine has big movement. If they are bad, the side of engine will move up

If that's all good, then to resolve vibration issue at stoplights (considering there are no codes), replace spark park wires. Ask how I know