M104, E320 Engine Surge,Update #4
 

After warmup the engine will surge, never cuts off. Thought I had some bad fuel. Drained fuel tank and changed filter, no change. Any ideas?

1996 E320 120,000

There can only be three (3) causes:

1. vacum leak via a hose or intake manifold seal

2. Bad mass air meter

3. Bad throttle actuator

Or a sticking throttle linkage. I have had a number that the linkage wouldn't come all the way home causing a surge.

Thanks, Suginami and Stevebfl. I will check those items first thing in the morning. Norm in FL

I only had a short time today to check things out. It looks like the throttle linkage is Ok,will ck closer tomarrow. The Ck. Eng. light never came on.If there was a misfire, or the Mass air sensor were bad I thought the ck.eng light would lite?I need to change the ATF so I will be checking for vaccum lines at the same time.Norm

1996 E320 120,000
1987 300D 230,000 totaled
1983 300D 268,000 sold

What is your surge like? Does it rev up and down? How is it under load (A/C or Defrost on)?

Matt
94 e320

Just to summarize my experience with the same problem:

After replacing the Mass air meter ($300-ish), and the throttle actuator ($1,400-ish), it was discovered that I had a vacum leak at the intake manifold gasket ($440.00).

I've learned from this forum that my kind of vacum leak is unusual.

If your problem is a vacum leak, there are other sources of vacum leaks that are more typical, like at the switch over valve at the front of the engine.

Mass air meter and throttle actuator failures are much more common.

Update: The surge starts after the eng. warmes up. I drove it today for about 5 min. no surge, parked it in the driveway. After idle for 4-5 min. the tach would start at 700 rpm drop to 500 then back to 700. It will do that two or three times then smooth out about 2-3 min . then surge, smooth out then surge. I changed the ATF today. The vaccum line to the transmission looks OK. I did lube the throttle linkage , It looks like it is returning to home . I was going to ck the vaccum but ran out of time. Will ck it later. By the way A/C on or off same. Norm

1996 E320 120,000

Well,

My car fluctuated the same way.

When cold, the idle was fine. After 2-3 minutes, the idle started fluctating wildly.

I guess it took that long for the intake manifold gasket to start leaking....

Update #2. I checked the vaccum today. Some of the information on Alldata is good! The info to check the vaccum helped me find the first indication. The vaccum was good at start 19-20 HG. Then it stsrted to vary 2-3 inches indicating ignition problem. Got my trusty tester out and checked spark puug wires. When the RPM drops No spark for just a sec. then spark again. Now What about the Overvoltage protector relay? Or something else? Cannot locate that OVP relay . It is not in the relay box under hood on pass. side. Where is it? Norm

1996 E320 120,000

No OVP.

If your are having a misfire instead of a surge the positibilities are a whole lot different. I usually replace the plug connectors under the three coils if you have HFM as I think a 96 should be. They are hard to diagnose and are cheap and are atleast 50% of all misfire problems.

Stevebfl, It seams to be all the plugs misfiring, not at the same time. I can put the tester on each wire and it does the same thing. It appears that it may be the spark signal? I shall change the plug connectors for a start , Thanks. Norm

1996 E320 120,000

Just for the hell of it take the crossover pipe off and clean the hell out of the EA with carb cleaner.



Joe

Update#3 Changed the sparkplug wires today. While changing the wires I noticed the vaccum line going to the EGR valve was just touching the elbow but not in the elbow. Well I changed the wires and reconnected the vaccum line,need a new one too short.Now the engine runs without surging. YES! Norm

1996 E320 120,033 mi.

Update *4 After replacing the plug wires and boots and reconnecting the vaccum line to the Air Injection Pump not the EGR valve ( my mistake). The surg is gone. Now the Ck. Eng.lite comes on. Code P0170 , Fuel trim malfunction. Now I have to track that down. Injectors I guess. Norm

1996 E320 120,070mi.