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  #1  
Old 06-26-2007, 12:26 AM
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S350TD Acceleration and power uphill: Am I expecting too much?

Recently bought a 1994 S350TD with factory replaced engine with 18K miles on it. Drove to Lake Tahoe via Echo Summit 5% grade and 7500 feet. Wouldn't go any faster than 45mph with full throttle and maximum rpm about 3400. Pulled over to let car by and from a stop was only able to reach 30mph with slow acceleration. Filters OK and recently changed. No other obvious problems. Runs smoothly at 70 to 80 mph on open road. Interestingly, it accelerates best when cold and then seems to lose power on acceleration when warmed up. I know it's a heavy sedan and somewhat underpowered but I would hope for better power and acceleration. Am I expecting too much?

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Old 06-26-2007, 12:32 AM
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You should be able to climb a 5% grade at 65 mph in fourth gear (2600 rpm) with the vehicle lightly loaded.

Anything below this level of performance indicates a problem.
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Old 06-26-2007, 02:14 AM
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Have you checked IP timing? What's the 0-60 mph time?

What does the engine temp gauge read when it's pedal to the floor on a steep climb?

Can you hook up a boost gauge? It's possible the EDS doesn't like something about the climb and is cutting back on boost. I'd sooner live with EGR than let the ECU determine when to allow boost. I replaced the vacuum wastegate actuator with a conventional pressure wastegate actuator in my SD.

Brian, what are the symptoms of a frozen IP timer? Do those things ever fail?

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Old 06-26-2007, 02:16 AM
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If it's lack of boost, maybe there's a leak in the wastegate vacuum circuit.

Sixto
93 300SD 3.0 - comatose
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Old 06-26-2007, 09:25 AM
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Sounds like the right maximum velocity if the ALDA isn't getting a boost signal in a 350 (its FAR more dramatic in a 350 than a 300).

Power should see a dramatic drop-off at about 3500 rpm.
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Old 06-26-2007, 10:23 AM
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Quote:
Originally Posted by sixto View Post

Brian, what are the symptoms of a frozen IP timer? Do those things ever fail?

Sixto
93 300SD 3.0 - comatose
The symptoms would be lack of power to some degree due to the late injection. But, I've never experienced it so, can't comment on how much power would be lost.

I don't think it's a common problem since the timer is strictly mechanical in nature.
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Old 06-26-2007, 01:53 PM
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Thanks for all of our replies. I had 3 passengers plus myself and some luggage at the time of our trip. Engine temperature did climb a bit over 100 degrees celcius during this particular climb but otherwise is pegged just above 80 degrees as a rule. We did have to climb a steep driveway at the end of the trip maybe 75 feet in length and I was worried that the car almost wouldn't make it even in low gear. On one other occasion with 2 passengers up a relatively steep country road about 8-10% grade about 100 yards or so, the car seemed to struggle and could only manage about 20mph with full throttle.
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Old 06-26-2007, 01:56 PM
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Originally Posted by bluhorizan View Post
Thanks for all of our replies. I had 3 passengers plus myself and some luggage at the time of our trip. Engine temperature did climb a bit over 100 degrees celcius during this particular climb but otherwise is pegged just above 80 degrees as a rule. We did have to climb a steep driveway at the end of the trip maybe 75 feet in length and I was worried that the car almost wouldn't make it even in low gear. On one other occasion with 2 passengers up a relatively steep country road about 8-10% grade about 100 yards or so, the car seemed to struggle and could only manage about 20mph with full throttle.
Have to get a boost gauge on it and see what you've got. It sounds like you're not getting any boost to the ALDA.

Or, just remove the ALDA and be done with it. It will transform it into a completely different vehicle.

Don't know if the W140 has any computer controls that will affect this modification. Sixto can advise.
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Old 06-26-2007, 02:49 PM
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My E300 cruises at 75+ up that summit, in 5th gear, loaded with five people and a trunkload of suitcases. Flooring the throttle is not required at all. Its 606 isn't that much more powerful than a 3.5L 603, although the E300 is 1000 lb lighter than the S350 (3600 vs. 4600 lb).

Something is definitely wrong, you are not at all expecting too much.
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  #10  
Old 06-27-2007, 12:09 AM
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Now that I've been alerted that something is not right, I've given closer attention to the car's behavior on acceleration. When cold and first starting up and flooring the accelerator, the car has great acceleration. At about 2500 rpm, there is a surge of acceleration which must be the turbo coming on. The car has noticeable torque and easily speeds up and shifts to a higher gear at about 3600 rpm. Upon repeated acceleration, there is no noticeable boost but the car continues to slowly acceleration with rpms reaching 4200 before downshifting. This is the situation that seems to occur when I was driving uphill to Tahoe and other times. The car doesn't feel like it has much torque and struggles when the load is increased.

Is this a sign that there is some problem with the turbo no turning on properly? What are possible causes of this?

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