My engine...what's wrong!?

[cawimmer430]

Thanks for all the help so far. 

[FoMoJo]

It's a bit odd (telling) that it happened quite suddenly.  From your description, it sounds like it could be a dead cylinder (not getting spark or the sparkplug fouled).  I would be inclined to pull the plug wires one by one and see which one didn't make any difference, then pull the plug to see if it's fouled.

[hounddog]

I would be inclined to ...

Drive it to a mechanic. 

[FoMoJo]

  Drive it to a mechanic. 

No fun doing that.  Just a whole lot of aggravation and money .

[hounddog]

As opposed to doing it yourself which is still a whole lot of aggrevation and money.

I would use the free time to drink, that way the aggrevation would be proportionately less as counted by the number of beers!

[cawimmer430]

I think I will have someone take a look at it. There's a friend of my fathers who lives close by. I phoned him up a few hours ago. Tomorrow he can help me out. 

[GoCougs]

Well, take this anecdote for what it's worth, but I had the exact same symptoms with a bad tank of gas (from a gas station that had been flooded).

[Cobra93]

I've never seen that cause a problem for the individual, have you?

Have you ever leaned against a car and grabbed a plug wire while the engine is running?

[Cobra93]

So then I tried again. This time I extended the firing sequence and also pumped the gas pedal - only then did the engine start but in P or N the RPM was fluctuating between 900 and 400 (!!!) RPM.

UPDATE!!!

I just started the up the 500SL to see if it would start and if the problem was still there. Amazingly the car started up right away, no hassle at all. And the engine was idling smoothly at precisely 900 RPM. "Had to problem gone away by itself?", I thought.

The transmission was in "P" so I press the accelerator slowly and give it a very light rev up to about 1,200 RPM. That's when the trouble started again.

I could be way off base here, but doesn't it seem like the problem is related to gas pedal movement? Therefore, I ask again: Does this fuel injection system have some variation of a throttle position sensor?

[S204STi]

Have you ever leaned against a car and grabbed a plug wire while the engine is running?

Yes, but just leaning against it while spraying doesn't seem to have the same impact... maybe so, I'll have to give it a try sometime.

[Cobra93]

Yes, but just leaning against it while spraying doesn't seem to have the same impact... maybe so, I'll have to give it a try sometime.

Let me know how that works out for you there, Sparky  

BTW, what's your take on my TPS theory?

[cawimmer430]

I could be way off base here, but doesn't it seem like the problem is related to gas pedal movement? Therefore, I ask again: Does this fuel injection system have some variation of a throttle position sensor?

I honestly don't know. I know our E320 has it but the 500SL? No idea. It's 1989 model if the date helps. It might have it, it might not. 

[S204STi]

Let me know how that works out for you there, Sparky 

BTW, what's your take on my TPS theory?

Anecdotal I know, but I've seen all of one or two TPS failures in my four year stint as a tech. Obviously others with more or different experiences may have seen more of them.  Take that for what it's worth.  As for the symptoms, I think a TPS would cause a flat spot or a shifting issue, but not necessarily a rough idle.  Just my .02.

[Cobra93]

Anecdotal I know, but I've seen all of one or two TPS failures in my four year stint as a tech. Obviously others with more or different experiences may have seen more of them.  Take that for what it's worth.  As for the symptoms, I think a TPS would cause a flat spot or a shifting issue, but not necessarily a rough idle.  Just my .02.

I know they'll cause a wandering idle. I'm thinking that if it is a bad TPS. it could be telling the computer that the car is at half throttle or more when the throttle blade is actually almost completely closed at idle. That might cause it to run super rich and surge like it's doing. 

[S204STi]

I know they'll cause a wandering idle. I'm thinking that if it is a bad TPS. it could be telling the computer that the car is at half throttle or more when the throttle blade is actually almost completely closed at idle. That might cause it to run super rich and surge like it's doing. 

Yeah maybe you're right.  Electrical problems can manifest in all kinds of odd ways.  Hopefully Wimmer gets it to a shop and we get an answer on what cased it.

[93JC]

...

Idle air controller?

[S204STi]

...

Idle air controller?

Possible as well.

[Raza]

I'm hoping it's fuel lines.  I haven't gotten one right since Payman's voltage regulator. 

[S204STi]

I'm hoping it's fuel lines.  I haven't gotten one right since Payman's voltage regulator. 

Internets diagnosis is always a crap shoot.

[93JC]

Even real diagnoses are often crapshoots.

[S204STi]

Even real diagnoses are often crapshoots.

All too true.

[Raza]

Any update, Wims?

[cawimmer430]

Any update, Wims?

Just came back from M?hldorf with the BMW 118i. The 500SL survived the journey back and the funny thing was the engine felt totally fine. 

When I started the car up after school there were no serious deviations in RPM. Though I did notice that in traffic while the transmission was either in "D" or "N" the car "sometimes" vibrated heavily when the RPM went under 500 to 400. When you leave Munich in the direction I took there's an Autobahn and I pushed the 500SL all the way to 180 km/h and the engine felt fine and responded nicely. I couldn't detect a problem with the ignition system. I really don't know what the problem was.

Right now my dad is handling the problem. He'll tell me what might be wrong with the car. One of his buddies who fixes up cars thinks it might indeed be a minor problem with the ignition system and some "regulator system" that might be "confused" at the moment. Updates will follow. 

[hotrodalex]

I would get a new tank of gas before you do much.

[cawimmer430]

I would get a new tank of gas before you do much.

The tank was 3/4 full when I left Munich and I drove very fast and aggressively doing lots of kickdowns (to give the engine a workout). When I arrived in M?hldorf the tank was almost at half full. My dad will burn up the rest. 

[AutobahnSHO]

Internets diagnosis is always a crap shoot.

Someone webz-diagnosed a bad crank sensor on my SHO based on the fact that it stalled (for a half second) on cruise control highway driving ONE TIME then intermittently wouldn't start a week later.

(that car had a known problem with those though.. :) )

[S204STi]

Someone webz-diagnosed a bad crank sensor on my SHO based on the fact that it stalled (for a half second) on cruise control highway driving ONE TIME then intermittently wouldn't start a week later.

(that car had a known problem with those though.. :) )

yeah, different issue.  I could tell you that a Buick that cycles power on/off constantly with the key on has a bad ignition switch, but that's just because it's a problem I've seen before.