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Discussion Starter #1
Ten days ago+-(100 miles ago) travelling at 70mph, cruise on, the engine skipped a beat, like the fuel shut off, the ignition failed on all cylinders, or there was water in the fuel line. It was a split second event, a hiccup. :eek:

A week later it happened twice in 2 minutes, same circumstance, hiway, cruise on, 70-75 mph.

Next day it happened coming off a traffic light after I exited a freeway.

Yesterday, it happened again on the interstate, at 70mph, and then actually stalled at a traffic light a few minutes later. It restarted perfectly.
Now I have a CEL on the instrument panel. :crybaby2:

This vehicle runs exceptionally well, shifts smoothly, no heating/cooling issues, no hesitation on acceleration, nothing to indicate a malfunction like this. It's not a single plug or wire type of miss, it's a system wide failure.

It's just a split second blip, like a miss or a tug, but it obviously is becoming more frequent. Occurs after 3-8 miles of driving.

The second time it happened I thought maybe the tranny was hunting for 5th gear, so I added a 1/2 quart of tranny fluid thinking it was possibly low. That didn't solve the issue. (Thank you Benz for eliminating the tranny dipstick!)

Has anyone else experienced this sorta' hesitation?

I've spent over an hour researching this on the forum, but nothing came up similar to my symptoms.

107k miles on the vehicle, it's a sweet ride, not a beater.
Could a wonky wheel sensor tied to the ASR cut the fuel momentarily? If I were to guess(and I am guessing!) I'd say it is an ignition issue rather than a fuel issue. MAF in very early stages of failure?
THOUGHTS?? :confused:

Now how do I clear the CEL? I can't find a link on that.
 

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Sounds like a CPS. Timing engine sensor at the back of the engine.

Works fine cold/first start of the day, and then nothing when hot.

The CPS can be a easy 10min DIY, or 10hr or so job if it is a metal sleeve sensor that is corroded on the engine...

By the way, what are the codes..?

http://www.benzworld.org/forums/r129-sl-class/1541905-m119-crankshaft-position-sensor-r-r.html

w140 Rear Crank Position Sensor / RnR nightmare - PeachParts Mercedes ShopForum

https://www.pelicanparts.com/techarticles/Mercedes-W129/37-ENGINE-Crankshaft_Position_Sensor_Removal/37-ENGINE-Crankshaft_Position_Sensor_Removal.htm

Martin
 

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Discussion Starter #3
CPS Failure Possibility

Sounds like a CPS.

Works fine cold/first start of the day, and then nothing when hot.

By the way, what are the codes..?

Martin
Thanks for the super quick response, Martin!

As I've studied this CPS issue in learning about these Mercs, I honestly cannot say this is EXACTLY what most people report for symptoms, i.e. the "Classic failure".

I do understand how this total loss of power COULD be related to the CPS, as it is an electrical choke point so to speak, however I'm not experiencing any " "hard starting when hot" symptoms. Ever!
Are you saying this "miss" is an early symptom of CPS failure?

Sorry, I don't know how to pull codes on the beast, I did seek the info provided by a HUM device attached to the plug under the dash, OBDII, and HUM tells me there are no malfunctions.

I'm not pressed to do something today, I have a back up ride.
I'll research "pulling codes" later today, and that should point me to the exact issue, correct?
My W124 had the OBD I and blinking lights so it was much easier to diagnose.

What you advise certainly makes sense, and the links were terrific. I thank you. :thumbsup:

Al
 

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I have observed the exact same thing a few times over the past 12 years, fairly intermittent and not dependent on speed, engine or ambient temperatures. Never had any check engine lights though, and STAR never showed any errors.
 

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Al

The car is OBDII compliant. As suggested, stop by any autoparts store and they can read as well as clear the code/codes. It's free and eliminates all the guessing.

Jim

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Al,

Mine displayed exactly the same behavior when I got it, like it shuts down for a split second and then goes on as if nothing had happened. Most of the time it doesnt cause a problem, but if it happens when your going slow it may stall completely. It used to happen once or twice a day. It didnt throw a CEL. It was the MAF sensor. SDS showed a MAF error so I swapped the one off my parts car and it's never happened again.
CEL can be cleared by most any handheld OBD2 scanner or autozone.

Hope this helps.

Mike in ABQ
 

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Thanks for the super quick response, Martin!

As I've studied this CPS issue in learning about these Mercs, I honestly cannot say this is EXACTLY what most people report for symptoms, i.e. the "Classic failure".

I do understand how this total loss of power COULD be related to the CPS, as it is an electrical choke point so to speak, however I'm not experiencing any " "hard starting when hot" symptoms. Ever!
Are you saying this "miss" is an early symptom of CPS failure?

Sorry, I don't know how to pull codes on the beast, I did seek the info provided by a HUM device attached to the plug under the dash, OBDII, and HUM tells me there are no malfunctions.

I'm not pressed to do something today, I have a back up ride.
I'll research "pulling codes" later today, and that should point me to the exact issue, correct?
My W124 had the OBD I and blinking lights so it was much easier to diagnose.

What you advise certainly makes sense, and the links were terrific. I thank you. :thumbsup:

Al

Everything you posted I went through with my 2002 W210, so that is why I replied to your post. Except I did not get any codes or lights.

Martin
 

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Discussion Starter #9
MAF Was My 1st Suspicion

Al,

Mine displayed exactly the same behavior when I got it, like it shuts down for a split second and then goes on as if nothing had happened. Most of the time it doesnt cause a problem, but if it happens when your going slow it may stall completely. It used to happen once or twice a day. It didnt throw a CEL. It was the MAF sensor. SDS showed a MAF error so I swapped the one off my parts car and it's never happened again.
CEL can be cleared by most any handheld OBD2 scanner or autozone.

Hope this helps.

Mike in ABQ
I've experienced failed MAF's on Subaru's. Slightly different symptoms, but that sudden BLIP, then normal behavior got me thinking.

I knew a failed CPS would give a hard start when hot symptom, but since it can shut down the electrical system, it certainly is a suspect.

I'm off this AM to an auto parts for the code check. I'll report back for an update.

Thanks to everyone with an input, I knew there had to be others with the same symptom. :goojob:
 

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Discussion Starter #10
Update On Engine Hiccup/CEL

I went to start the vehicle to run down to the auto parts just a few minutes ago. The CEL immediately went off. Car ran the usual wonderful, and I drove to the auto parts. The very knowledgeable manager there said he couldn't check the codes since the CEL was off, and that he could not clear the codes even if he found a malfunction code. He says he cannot access a history of malfunctions. As it turns out Rico owns a '95 S600 in white/tan w/ 107K.

So I get home, and HUM had sent an email, informing me that it detected a code, P0100, MAF sensor with the CEL lamp. It didn't detect the CEL/code till I started the car today.

I think I better check my air filter. I have a funny feeling that it may be dirty, since I never checked it since purchase. :nerd
 

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Discussion Starter #12
Mechanic In A Can

Knock on burlwood, I think cleaning the MAF did the trick. :thumbsup:
A $9 can of cleaner, a 25 mile test drive, and no more hiccups.

The dealer wanted $44 each for air filters, mine didn't look too bad, so I passed on that. The MAF didn't look dirty at all, and the throttle body was spotless. I suppose that MAF is just super sensitive to contamination.

I sprayed the MAF liberally, waited 30-40 minutes, and set out for a trial. Zero symptoms.

Thanks to everyone who offered advise, googling MAF failure symptoms drew the same conclusions, BTW.

If you choose to try this yourself be aware that:
I did lose a 7mm open end/box end that slid under the intake manifold while I tried to loosen the clamp under the MAF. :banghead:
And then the MAF would rotate, but I couldn't remove it. I just sprayed it in place and slapped it all back together. It was very awkward leaning over that huge engine working in tight spaces.
 

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Knock on burlwood, I think cleaning the MAF did the trick.
A $9 can of cleaner, a 25 mile test drive, and no more hiccups.

The dealer wanted $44 each for air filters, mine didn't look too bad, so I passed on that. The MAF didn't look dirty at all, and the throttle body was spotless. I suppose that MAF is just super sensitive to contamination.

I sprayed the MAF liberally, waited 30-40 minutes, and set out for a trial. Zero symptoms.

Thanks to everyone who offered advise, googling MAF failure symptoms drew the same conclusions, BTW.

If you choose to try this yourself be aware that:
I did lose a 7mm open end/box end that slid under the intake manifold while I tried to loosen the clamp under the MAF. :banghead:
And then the MAF would rotate, but I couldn't remove it. I just sprayed it in place and slapped it all back together. It was very awkward leaning over that huge engine working in tight spaces.
Al

What codes showed up when you had them pulled?

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Discussion Starter #14
Code For MAF Failure

Al

What codes showed up when you had them pulled?

Sent from my XT1080 using Tapatalk
I went out to drive the vehicle to an auto parts store the next day and the CEL disappeared the moment the engine started. When I got to the store the fella said he couldn't read the codes if the CEL was off, and he couldn't pull history of codes, nor could he reset codes. :confused:

When I arrived back home, HUM had sent me an email advising me that the vehicle had tripped a P0100 code and offered several suggestions and an explanation about the code.

I drove the car several miles that day, and sure enough it was hiccuping about every 3-4 miles of city driving. It didn't stall or trigger a CEL. :(

No guarantees I'm outta the woods with the cleaning solution, there may be a catastrophic failure looming down the road, but so far it appears the problem is solved. At least I'll recognize the symptom should it reappear.
 
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