Need help 99 SL acting up
 

This one got me. My sweet 99 SL with 58,000 miles, after new motor mounts, changing several cracked vacuum hoses, maf gaskets above and below the elbow, air breather filters, lubricating vacuum fittings, still idles rough, worse than before the motor mounts were changed. it runs great otherwise and according to my mpg gage getting better gas mileage than ever, right now it's going thru a tank of premium laced with Techron additive since it was recomended by the forum techs, since the engine decided to knock for a few seconds at start-up when the weather is 50F or below, that still happening too. It idles around 750 rpm and it shakes, no check engine light, it shakes at the stop light but not as much, I've tested it with the brake pedal depressed to see if the drop in vacuum will change anything, with the climate control on also but it did not, vacuum leak was my theory, I do hear the climate control Y11 vacuum control valve clicking constantly.
Any ideas, any help will be appreciated.

long shot but....
 

Carlos:

No experience with MB as I've been owner of my 99 for only a few months...but I did have 94 BMW 530 that had the same ignition coil spark plug set up as the SL that caused rough idle. Two problems causing rough idle were spark plug boots between coils and spark plugs hardened and caused arching along with the valve cover leaking oil into spark plug well. You may want to pull coils and inspect boots and see if you have an oil leak. May also change the plugs while your at it. Finally not sure if theres a way to use ohm meter for each of the coil packs and compare specs between each of them.

Good luck.

Charles

I'd go with the jumper leads / coil packs. They can be connected to the diagnostics and voltage cycles be measured - hopefully just a new lead.

99
 

No visible cracks, no arcs and thank God no oil leaks, ran a plug wire tester that detects any arc outside the insulation found none.
plugs maybe? 58,000 on the clock, this plugs are suppose to last 100,000 miles but then again anything is possible.
Any ideas anybody? Taking the car to the dealer will be the very last option,
rather exaust every conventional route first

Have you measured the current and voltage from the coil packs? The plugs need changing every 40k miles - again depending on how it has been driven - that's Mercedes recommendation anyway. At 58k if they haven't been done I'd do that as a matter of course. NGK Iridium are good replacements.

99 Sl
 

Went to the dealer to schedule a computer diagnostics on my car, got there to late in the day, service advisors were on the way out the door, talked to the tech in charge of the SL's, he told me that if this was his car he would'nt do anything to it until he change the spark plug wires, that just about every complaint about rough idle in this engines is due to bad plug wires some with as low as 20,000 miles on the clock.
So we are on the right track stats007, I will change the wires first to see if there is any improvement before I change the plugs, at $20.75 a piece and 16 of them,I will not change them if I do not have to, I've change many plugs in my time but I've never dealt with this metal sleeves around the plugs, do they just twist and pull out, special tool?
Spark plugs Bosch $20.75 ea. Dealer
$10.28 Fast Lane
Wire set OEM $378.53 Dealer
$285.94 Fast Lane
I hate to sound Frugal (cheap) but I'm getting married in 2 weeks and money is thight.

This is what I mean about getting it on a diagnostic machine - they can measure each wire individually and tell you what ones need replacing. The way to remove them is to get a long 17mm spanner and lever them off using the intake manifold as a fulcrum - this is after you have removed the intake assembly (vanity cover and filter housing). They make a special tool to do it - though looks like a spanner to me!

SL acting up
 

Change plug wires no dice the engine still idles rough.
Bought a mitivac I will test every vacuum hose, fitting, assy, actuator etc before I change the plugs just to be sure I did'nt miss anything, wish me luck.

Good luck buddy. It sounds like you have been having problems with your car since you bought it. I hope that you find the source of the problem.

Also, I think you have the newer V8, not the M119, so it should be easier to diagnose the problems with the computer at the dealer.

This engine has a coil pack on each cilinder,there is no plug wires!!!
Are you sure what r u doing?

Sl
 

It has 8 coil packs with two plug wires each per cylinder 16 spark plugs and no I'm not sure I know what I'm doing because is not working like I expected.

So how did you change all 8 of the plug wires?:confused:

I thought hat iw was like my ML320. The plug wires and the coils are one unit, you just have to replace them all at once. I am not sure if that is how it is in your car, but I am just confused.

The M113 has 16 jumper leads that run from the 8 coil packs to the spark plugs. These leads can all be changed seperately.

99 Sl 500
 

It is a 1999 SL 500 with 113 engine 58,000 on the clock, 3 valves per cylinder, 2 plugs per cylinder.
I bought a complete set all 16 wires and replaced them, they can be purchased individually but that did'nt make any sense to me, with the exeption of the metal sleeve they look, feel and install like spark plug wires, the box is label as ( ignition wire set)
They did make a difference in the idle but it did'nt cure it so I'm still scratching my hard head, the smart thing to do will be to let the dealer fix it
but I'm getting married Friday and my money does't belong to me anymore, at least not for a while, I would really like to solve this with my hands, is becoming more than a challenge and I pay attention to all recomendations that you guys give me.

If you had an actual misfire there would be a check engine light. You likely need the sensor gear adaptations reset for smooth running. Take it to a dealer, or good indie and tell them that the engine mounts were replaced and the adaptations need reset. Not the mixture adaptation, but the sensor gear adaptation.