SL/R129 99 500SL HELP - MBWorld.org Forums

Jul 31, 2019 | 02:53 PM

rscruggs2

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From: Linn County MO

SL500

99 500SL HELP

My '99 (55,000 Mi) is doing weird things. I can start it up and drive 1.5 miles to town and when you try to accelerate the RRM's go down. Then I stop at the convenience store and the idle is chugging and < 500RPM. Then I shut the engine down, restart and presto, everything works fine but the Check engine light is still on. We put it on my mechanic's diagnostics reader and it says to change 345&7 power packs. We both think this can't be right and the controller may be working intermittently. Has anyone else had this problem? Rick.

Aug 1, 2019 | 09:04 AM

sutliffe

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From: Epping,NH

1998 SL500

Do you know if the power packs are original equipment? I would replace two and see if any substantial improvement. If so replace all.
I had a similar problem There are a lot of crap parts in the market place, Use only good quality parts and country of origin..... mot no name junk.
Good luck.!

Last edited by sutliffe; Aug 1, 2019 at 09:06 AM.

Aug 1, 2019 | 04:14 PM

rscruggs2

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Junior Member

Joined: Aug 2013

Posts: 40

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From: Linn County MO

SL500

[QUOTE=sutliffe;7817601]Do you know if the power packs are original equipment? I would replace two and see if any substantial improvement. If so replace all.
I had a similar problem There are a lot of crap parts in the market place, Use only good quality parts and country of origin..... mot no name junk.
Good luck.![/QUOTE

Yes original equipment less 2 which are OEM. The thing is, that I started it this morning and the Check engine light was out and it ran perfectly. This leads me to believe there is a short somewhere in the computer or between the computer and power packs. If it were bad power pack/s it would run poorly all the time....yes? The car has but 55,000 miles on it. Do you know the name of the computer that distributes the voltage?

Aug 1, 2019 | 07:32 PM

sutliffe

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Joined: Oct 2014

Posts: 68

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From: Epping,NH

1998 SL500

Replace them

I believe the coils are braking down under load and heat. Change out the coils and your problem will probably go away.

Aug 1, 2019 | 07:43 PM

bobterry99

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From: Atlanta, unfortunately

'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55

Quote:

Originally Posted by rscruggs2

We put it on my mechanic's diagnostics reader and it says to change 345&7 power packs.

It may seem highly presumptuous for me to write this, but the diagnostic computer surely does not say to change any "power packs". The hardware and software necessary to make such a pinpoint diagnosis does not exist, and the diagnostic computer is not clairvoyant.

I would swap the coils from cylinders 3, 4, 5 and 7 with the other four cylinders and see if the diagnostic codes you have move with the coils or remain. If they remain, then I would do the same swap with fuel injectors.

Aug 2, 2019 | 06:36 AM

rscruggs2

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Junior Member

Joined: Aug 2013

Posts: 40

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From: Linn County MO

SL500

That sounds like a plan, I call the ignition coils power packs for some reason. I never thought about the fuel injectors.....what side of the engine is 3,4,5 & 7?

Aug 2, 2019 | 08:17 AM

bobterry99

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From: Atlanta, unfortunately

'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55

Quote:

Originally Posted by rscruggs2

what side of the engine is 3,4,5 & 7?

This is probably correct: https://mbworld.org/forums/s55-amg-s...rder-m113.html

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Aug 3, 2019 | 03:24 AM

Ahmed

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Joined: Apr 2002

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From: Bahrain

R129 SL55 AMG & W208 CLK55 AMG

Sounds like coils to me too.

Aug 3, 2019 | 12:33 PM

#10

rscruggs2

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Joined: Aug 2013

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From: Linn County MO

SL500

If it starts acting up again we are going to take Bob Terry's reasonable recommendation. Knock on wood the car hasn't missed a beat in 3 days now. I love this car.

Aug 3, 2019 | 12:53 PM

#11

bobterry99

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From: Atlanta, unfortunately

'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55

It's counter-intuitive to people who compare engine peak horsepower and who know that Chrysler "merged" with Daimler-Benz in the summer of '98, but the '99 and later 500s are the best.

Last edited by bobterry99; Aug 25, 2019 at 12:02 PM.