1994 S420 - No Power at Low Speeds
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Junior Member
Joined: Oct 2013
Posts: 15
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From: Tampa, FL
90 350SDL, 94 S420, 97 SL500, 97 S420
1994 S420 - No Power at Low Speeds
I have a good idle, but the car has no power taking off from a stop. Regardless of throttle position, the engine will barely speed up under load and the car does move forward, but quite slowly. No missing, noises, etc., just no power.
One you get the car up to about 20-30 mph, it goes forward without a problem and seems to run just fine. You can drive it at freeway speeds without an issue. Slow down to a stop or below that 20-30 mph threshold and it acts like it has no power.
I'm satisfied that everything in the way of the MAF, ETA, plug wires, distributor caps/rotors are OK. The problem seems like there is no change in engine timing regardless of throttle position.
I'm getting a CEL all the time, yet the DAS shows random codes, such as knock sensors or ignition coils. I attribute these to occurrences at low speeds with the throttle at or near wide open. I can clear them without a problem and they'll come back again after I drive the car. Again, the codes are random and not at all repeatable. However, even if I clear them the CEL is on as soon as you restart the car. Strange.
So my question is, what exactly controls engine (spark) timing? I assume it's the EZL. I'm getting vacuum there, so I know that's right. I'm wondering if the camshaft or crankshaft sensor or pickup on the engine that is sending it information about the engine position that it might not be seeing.
I'm not in "limp home" mode that I can tell, as there is no limit on speed or RPM.
I'm about to have the car taken to a local shop for diagnosis, as I've pretty much hit the wall on this. Anything the collective wisdom of the group has to add would be deeply appreciated.
Thanks,
Dan
One you get the car up to about 20-30 mph, it goes forward without a problem and seems to run just fine. You can drive it at freeway speeds without an issue. Slow down to a stop or below that 20-30 mph threshold and it acts like it has no power.
I'm satisfied that everything in the way of the MAF, ETA, plug wires, distributor caps/rotors are OK. The problem seems like there is no change in engine timing regardless of throttle position.
I'm getting a CEL all the time, yet the DAS shows random codes, such as knock sensors or ignition coils. I attribute these to occurrences at low speeds with the throttle at or near wide open. I can clear them without a problem and they'll come back again after I drive the car. Again, the codes are random and not at all repeatable. However, even if I clear them the CEL is on as soon as you restart the car. Strange.
So my question is, what exactly controls engine (spark) timing? I assume it's the EZL. I'm getting vacuum there, so I know that's right. I'm wondering if the camshaft or crankshaft sensor or pickup on the engine that is sending it information about the engine position that it might not be seeing.
I'm not in "limp home" mode that I can tell, as there is no limit on speed or RPM.
I'm about to have the car taken to a local shop for diagnosis, as I've pretty much hit the wall on this. Anything the collective wisdom of the group has to add would be deeply appreciated.
Thanks,
Dan
Thread Starter
Junior Member
Joined: Oct 2013
Posts: 15
Likes: 0
From: Tampa, FL
90 350SDL, 94 S420, 97 SL500, 97 S420
I would add that this condition started after the car had been parked outside in a damp area (next to a large open body of water) for about 10 days, during which we had about 10-15 inches of rain, too.
WDBGA43E8RA145626
Since you appear to have some DAS experience, how can I use the DAS/HHTWIN to "see" the EZL operation, or the signals coming into it?
Thank you,
Dan
WDBGA43E8RA145626
Since you appear to have some DAS experience, how can I use the DAS/HHTWIN to "see" the EZL operation, or the signals coming into it?
Thank you,
Dan
Last edited by lwb250; Aug 21, 2016 at 05:44 PM.
Junior Member
Joined: Aug 2004
Posts: 41
Likes: 3
From: Richmond, BC, CA
1990 560 SEL , 1998 S 420
Dan,
Could that be a bad batch of gas you got somewhere?
Partially plugged fuel filter and/or air filter?
Alternator output good under load?
Good strong and healthy battery?
Good ground wires all around?
...hmmm, are the brake calipers and/or the parking brakes binding? ...push the vehicle in "N"! Feel good about it? How about touch the rear wheel after a short drive? Hot to the touch?
Sorry to mention these obvious stuffs before suspecting other more involved areas. I think you can omit the Crankshaft position sensor 'cos the engine would not fire up if defective. Others may chip in on more advance in-dept areas.
...hope these help ;-))
richard
Could that be a bad batch of gas you got somewhere?
Partially plugged fuel filter and/or air filter?
Alternator output good under load?
Good strong and healthy battery?
Good ground wires all around?
...hmmm, are the brake calipers and/or the parking brakes binding? ...push the vehicle in "N"! Feel good about it? How about touch the rear wheel after a short drive? Hot to the touch?
Sorry to mention these obvious stuffs before suspecting other more involved areas. I think you can omit the Crankshaft position sensor 'cos the engine would not fire up if defective. Others may chip in on more advance in-dept areas.
...hope these help ;-))
richard
Thread Starter
Junior Member
Joined: Oct 2013
Posts: 15
Likes: 0
From: Tampa, FL
90 350SDL, 94 S420, 97 SL500, 97 S420
Dan,
Could that be a bad batch of gas you got somewhere?
Partially plugged fuel filter and/or air filter?
Alternator output good under load?
Good strong and healthy battery?
Good ground wires all around?
...hmmm, are the brake calipers and/or the parking brakes binding? ...push the vehicle in "N"! Feel good about it? How about touch the rear wheel after a short drive? Hot to the touch?
Sorry to mention these obvious stuffs before suspecting other more involved areas. I think you can omit the Crankshaft position sensor 'cos the engine would not fire up if defective. Others may chip in on more advance in-dept areas.
...hope these help ;-))
richard
Could that be a bad batch of gas you got somewhere?
Partially plugged fuel filter and/or air filter?
Alternator output good under load?
Good strong and healthy battery?
Good ground wires all around?
...hmmm, are the brake calipers and/or the parking brakes binding? ...push the vehicle in "N"! Feel good about it? How about touch the rear wheel after a short drive? Hot to the touch?
Sorry to mention these obvious stuffs before suspecting other more involved areas. I think you can omit the Crankshaft position sensor 'cos the engine would not fire up if defective. Others may chip in on more advance in-dept areas.
...hope these help ;-))
richard
Thanks for the suggestions.
We can rule nearly all of them out, as the car will run without a hitch at highway speeds. That would cover induction, fuel and brakes. I'm pretty comfortable with the electrical system being OK. I have access to a DAS/HHT system, and there are no error codes indicating anything wrong elsewhere.
I would agree with the assumption on the CPS. I've never seen one that was marginal, that is, they either work or they don't, and when they don't the car won't start.
Thanks again for the suggestions - it never hurts to ask, even the simple stuff.
Dan
Thread Starter
Junior Member
Joined: Oct 2013
Posts: 15
Likes: 0
From: Tampa, FL
90 350SDL, 94 S420, 97 SL500, 97 S420
DAS/HHT said the EZL or coil was bad - looking into actual values showed that the left distributor, or the cylinders it drives, weren't firing.
Swapped coils and the problem remained.
Checked wiring between the EZL and coils, OK.
Got a used EZL off of eBay for $100 and installed it this morning.
Car runs like new.
Dan
Swapped coils and the problem remained.
Checked wiring between the EZL and coils, OK.
Got a used EZL off of eBay for $100 and installed it this morning.
Car runs like new.
Dan
Junior Member
Joined: Jan 2015
Posts: 27
Likes: 2
S500 w140
I have a good idle, but the car has no power taking off from a stop. Regardless of throttle position, the engine will barely speed up under load and the car does move forward, but quite slowly. No missing, noises, etc., just no power.
One you get the car up to about 20-30 mph, it goes forward without a problem and seems to run just fine. You can drive it at freeway speeds without an issue. Slow down to a stop or below that 20-30 mph threshold and it acts like it has no power.
I'm satisfied that everything in the way of the MAF, ETA, plug wires, distributor caps/rotors are OK. The problem seems like there is no change in engine timing regardless of throttle position.
I'm getting a CEL all the time, yet the DAS shows random codes, such as knock sensors or ignition coils. I attribute these to occurrences at low speeds with the throttle at or near wide open. I can clear them without a problem and they'll come back again after I drive the car. Again, the codes are random and not at all repeatable. However, even if I clear them the CEL is on as soon as you restart the car. Strange.
So my question is, what exactly controls engine (spark) timing? I assume it's the EZL. I'm getting vacuum there, so I know that's right. I'm wondering if the camshaft or crankshaft sensor or pickup on the engine that is sending it information about the engine position that it might not be seeing.
I'm not in "limp home" mode that I can tell, as there is no limit on speed or RPM.
I'm about to have the car taken to a local shop for diagnosis, as I've pretty much hit the wall on this. Anything the collective wisdom of the group has to add would be deeply appreciated.
Thanks,
Dan
One you get the car up to about 20-30 mph, it goes forward without a problem and seems to run just fine. You can drive it at freeway speeds without an issue. Slow down to a stop or below that 20-30 mph threshold and it acts like it has no power.
I'm satisfied that everything in the way of the MAF, ETA, plug wires, distributor caps/rotors are OK. The problem seems like there is no change in engine timing regardless of throttle position.
I'm getting a CEL all the time, yet the DAS shows random codes, such as knock sensors or ignition coils. I attribute these to occurrences at low speeds with the throttle at or near wide open. I can clear them without a problem and they'll come back again after I drive the car. Again, the codes are random and not at all repeatable. However, even if I clear them the CEL is on as soon as you restart the car. Strange.
So my question is, what exactly controls engine (spark) timing? I assume it's the EZL. I'm getting vacuum there, so I know that's right. I'm wondering if the camshaft or crankshaft sensor or pickup on the engine that is sending it information about the engine position that it might not be seeing.
I'm not in "limp home" mode that I can tell, as there is no limit on speed or RPM.
I'm about to have the car taken to a local shop for diagnosis, as I've pretty much hit the wall on this. Anything the collective wisdom of the group has to add would be deeply appreciated.
Thanks,
Dan
I think it all comes down to the battery. Get a new one and see what happens. I had a similar experience, didn’t want to go deep in troubleshooting so I just put a new battery and bam. Worked like a charm.
Thread Starter
Junior Member
Joined: Oct 2013
Posts: 15
Likes: 0
From: Tampa, FL
90 350SDL, 94 S420, 97 SL500, 97 S420
It wasn’t the battery or charging system. It was a bad EZL. Replaced it with a new one and all was well.
