Severe hesitation on acceleration from stop
 

Hi!

Recently purchased 1991 300CE (W124/M104), currently 108,000 miles. Over the last month I have replaced both transmission cooling hoses, Transmission Pan Filter & gasket, Spark plugs (bosch twin platinum), distributor cap, rotor, valve cover gasket, Upper timing seal gasket, Fan belt tensioner damper, fan belt, fuel filter. Timing chain and upper rail guide "looked" ok when I replaced the seal strip gasket 3 weeks ago.

I disconnected the battery when I changed the fuel filter and upon reconnection the MB was rough idling and hesitant on acceleration from stop. After about 3 days this problem cleared itself.

This past weekend I had to remove the steering wheel to locate a loose part in the bottom of the steering wheel. I disconnected the battery to avoid setting off the driver airbag.

When I re-connected the battery, the MB idled a bit rough and the hesitation problem resurfaced. The hesitation could almost be classified as a misfire at times but feels more like flooding.

Today, the hesiation exists but there is now a noise that sound like it might be coming from the timing chain area.

The hesitation is only upon acceleration from a stop. Once the car is moving there is no hesitaion, however; the noise is still there. (Sounds like a clanking noise)

I've done research looking for help on this issue to know avail.

Is there anyone out there who can help me in my pusuit. Any help would be greatly appreciated.

Thanks,
John:p

Have you had your fuel:ratio measured?

Intruder

Twin Platinums ?
 

We consistently read here about avoiding Platinum Spark Plugs and sticking with Copper Core.
I am not sure about your model, but with the 126 cars - using Platinum always effects Idling. You might want to consider replacing the Plugs. Hopefully that will do the trick.

Update
 

Haven't done anything with fuel/air mixture.

Yes, I have read some posts about platinum plugs (hindsight 20/20).

Seems the clatter is from the engine fan. Bit of a wobble. Only question I have now is, what is the difference between the fan clutch and the fan clutch bearing bracket?

Still, replacing the plugs is inexpensive-we know they work poorly and effect Idle - I say go for it...

The fan clutch bracket is the part that the fan clutch bolts to. The clutch is the part that the actual fan blades are attached to. If it is wobbling change the fan clutch bracket. For a competent diyer it is doable. Sounds like you already changed the tensioner. The fan clutch bracket is where the fan bearing is located and and in my experience they do need replacement around 105,xxx miles.
Dump the plat plugs and go with copper.

Update #2 Plus new question!
 

OK!

Final analysis of noise problem. Fan pulley has lost at least one bearing. Wobbles like a tree in the breeze.

Have ordered new fan clutch, clutch bearing bracket, pulley and removal tool.

Next question: Which way do you turn the allen bolt to remove the fan clutch? I've been told counter clockwise (conventional threads).

Also, ordered new Bosch plugs.

After fan is in working order will go to the hesitation problem.

One question I still have in my mind is that when I disconnected the battery didn't it remove all stored data in the computer chip. Hence, poor performance at initial start-up.

Would appreciate any responses.

Have a great day!

John

Final update this post
 

Hi!

Was succesful this past weekend in replacing fan clutch, fan pulley and the clutch bearing bracket. Bearing bracket was missing about 6 bearings........

Not too difficult! Thanks to Phil for all his help in getting the material and tools to me in a timely fashion.

If you need any parts....FastLane is the place to shop. Local Checker wanted $221 for the fan clutch!

Also, replaced the belt idler tensioner adjusting screw and swapped out the platinum plugs for Bosch Super plugs. No change in performance.....now to get that hesitation problem fixed.

John

:D

low rpm hesitation and rough idle on 91 300ce
 

I have read a great deal about low rpm hesitation and rough idle over the past 2 years. I had this problem and after replacing plugs, cap, rotor, o2 sensor, fuel filter, and enriching EHA, I finally was able to find the problem and fix it. Although I know that there are many things that can cause this problem, I was convinced from the get go that it was a fuel issue. Last week I pulled the plugs to check them and noticed that the #1 plug had some carbon on it while all the rest were super clean. I pulled the #1 injector and using carb cleaner with the red extention tip which fits perfectly in the injector end, cleaned the injector. I noticed some black stuff that came out and I continued spraying into the injector until I got a fan-like spray pattern...reinstalled the injector and after months of chasing these two problems, she now idles like new and is a rocket from dead stops. I truly hope this post saves someone time and money.