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Old 06-17-2005, 11:25 AM
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Join Date: Jan 2000
Location: Long Island, NY USA
Posts: 195
Code P0303 Power Loss on E55

Hey gang;
Need some advice here on where to start...
2000 E55, 46,000 miles, original plugs, wires. Replaced MAF and air filters about 2000 miles ago. Seems to be running OK with no pronounced miss or rough idle.
There is a noticable loss of power at highway cruising speed, 60MPH on up.
Engine seems to be running at a higher temp then normal. Sometimes, there is an coolant odor in the garage, no visable coolant loss.
Yesterday the check engine light came on with hard acceleration. Code P0303 and some random misfires stored. I reset the codes and the check engine light did not come back on.
I'm thinking of starting by replacing all the wires and plugs with copper core-or should I start by replacing juyst the #3 plugs and wires?
Any suggestions? Should I be looking somewhere else?

00 Silver/Black AMG E55
96 DCM Impala SS
94 Admiral Blue ZR-1
81 Candy Apple Corvette Cpe

Last edited by zrusny; 06-17-2005 at 11:47 AM.
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Old 11-29-2005, 04:10 AM
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Old 11-29-2005, 09:24 AM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Start by replacing the spark plugs, MB/Bosch suggest a MAXIMUN life of 5 years OR 100K which ever comes FIRST!

OR you could switch a coil & spark plug wires from a different cylinder & see if the problem moves to that cylinder!
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Old 11-29-2005, 05:07 PM
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Join Date: Jun 2003
Location: SF Bay Area
Posts: 599
Exclamation E500-Runnig hotter than normal

Originally Posted by zrusny
Engine seems to be running at a higher temp then normal. Sometimes, there is an coolant odor in the garage, no visable coolant loss.
How much higher is the engine temperature? Does the electric fan operate at varying speeds? You may want to have an "activation test" performed on the electric fan to ensure that it is cycling correctly. I worked on an ML500 last week that had visited numerous repair centers to cure a running hot problem. You name it and it was replaced, if not twice then 3 times, all to no avail. An activations test revealed that the electric fan was incapable of operating above 30% speed. Checked the PWM signal from the ME control unit, the fan control signal varied to the degree of activation. (IE: 1.5 V for low speed and 9.5 V for High) Performed a voltage drop test on the power and ground circuits, discovered 9.8 V on the main power lead from the 100A fuse attached to the battery terminal.

If your fan is not capable of operating from as low as 10% to as high 90% with several stages in between then I might suspect it may answer your “running hotter” than normal complaint.

FWIW: Just another .02 in the kitty
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Old 01-29-2006, 04:50 AM
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Join Date: Nov 2005
Posts: 7
Missing Adaption

After Changing The Missfiring Cylinders Wires The Car Was Doing Exactly What You Are Describing, Loosing Power And Such. All That Needed To Be Done Was To Reset The Crank Shaft Sensor Adaption. This Will Have To Be Done At A Dealer With Star Diag. Tester.all It Does Is Resets The 5 Operating Speed Ranges In The Ecm.this Is Not Common But In Certain Instances Will Need To Be Done When A Missfire Is Present.
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Old 01-29-2006, 11:08 AM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Sensor ring adaptation is reset to original coding by a scan tool, but actual adaptation is done on the road or dyno. It sort of takes a tool to know that one is in the load/rpm block to adapt the first block. After that the rest are left to adapt themselves. Untill some level of adaptation is achieved the controller won't recognize a misfire. Not that it couldn't, it just needs that level of adaptation for the software to allow it.

Full load misfires due to cat restrictions are common on that motor. I would probably replace the plugs as stated for the time reasons stated and then not do anything else till another code appears. I would probably also move the coil packs to an adjacent cyl and note that at the same time. If the problem has anything to do with cats or overall mixture, the misfire will likely appear on a different cylinder.

If a repeat misfire comes from the cylinder that now has the pack that was on #3 previously then I would replace the wires on that cyl and repeat the testing.

Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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