1994 S420 - No Power @ Low Speeds

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LWB250
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1994 S420 - No Power @ Low Speeds

Post by LWB250 » Mon 22 Aug, 2016 4:48 am

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.

Thank you,

Dan

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Bartman4800
300 SLR
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Re: 1994 S420 - No Power @ Low Speeds

Post by Bartman4800 » Mon 22 Aug, 2016 12:16 pm

Dan,

It might not be the engine at all.
Could it be that the traction control is malfunctioning and holds the engine back?
I think it uses the ABS sensors, but other people here are better informed.

Bart
1963 220 Sb Sedan "Kermit" (Australian Assembly)
1960 220 Sb Sedan "Zum Schlachten" (Early German Assembly, with a torsion bar spring for the bonnet) - Stored in Country WA
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LWB250
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Re: 1994 S420 - No Power @ Low Speeds

Post by LWB250 » Mon 29 Aug, 2016 12:46 am

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

CraigB
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Re: 1994 S420 - No Power @ Low Speeds

Post by CraigB » Mon 29 Aug, 2016 4:48 pm

good news, thanks for feeding that back.
Craig Baulderstone
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Ivanerrol
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Re: 1994 S420 - No Power @ Low Speeds

Post by Ivanerrol » Mon 29 Aug, 2016 10:56 pm

EZL? Are you sure your not talking about the ECU?

Here's the issue.
Your car falls into the years of the deadly eco faulty wiring harnesses.
Faults in the wiring particularly in the wiring between the coils and the ECU are known to blow out the latter.
As a matter of urgency I would have your wiring harnesses checked.
W211 - E240
W204 - C280
W210 - E240
Departed
W202 - C200, C180, C180
W126 - 380SE , 380SE (Ex SA Import), 560SEL
W124 - 300e, 260e (ex Japan)
W111 220s (Indonesia) 4 speed manual column shift
W123 230
W116 450SEL
W140 420SEL
W210 E240
W209 CLK 240
W201 190e 2.6 (ex U.K.)

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McGavin
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Re: 1994 S420 - No Power @ Low Speeds

Post by McGavin » Tue 30 Aug, 2016 12:22 pm

Abstract thought here, didn't the EZL/ECU control the transmission in these? Sounded like it was taking off in a tall gear, was it free revving out of drive?

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Ivanerrol
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Location: Melbourne

Re: 1994 S420 - No Power @ Low Speeds

Post by Ivanerrol » Tue 30 Aug, 2016 4:10 pm

Some cars got the 722.5 - no ECU control
Last of the series 722.6

Early cars had HFM ignition/injection

And the dreaded Eco wiring.

Issues with early cars were
Brake light switch
Abs sensors
Traction control
W211 - E240
W204 - C280
W210 - E240
Departed
W202 - C200, C180, C180
W126 - 380SE , 380SE (Ex SA Import), 560SEL
W124 - 300e, 260e (ex Japan)
W111 220s (Indonesia) 4 speed manual column shift
W123 230
W116 450SEL
W140 420SEL
W210 E240
W209 CLK 240
W201 190e 2.6 (ex U.K.)

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