450SL - Rough Idle and Slow Start. Are these symptoms related?

[supercanuck]

I am the proud owner of a 1980 450SL, which is my every day driver, but recently I have noticed a couple of things it has been doing and I'm wondering a) if anyone knows what may be causing them, and b) if they may be related.

1) Vibrating more at idle - Maybe it's just me, but in the last couple of weeks it seems like the car has been vibrating more at idle. It's not a rough vibration at all, in fact, it's pretty smooth, but it seems like it has gotten a bit worse as of late.

2) Slow off the go - also recently, it seems like when I punch on the gas, it takes a couple of seconds longer to catch up with itself before I can really feel it. When I hit it, I can hear the engine rev, but it doesn't get up and go right away.

For each of these problems, can anybody let me know what the cause of the issue is, and what may be able to be done to help?

Thanks!

[meltedpanda]

my first thought is to make sure all rubber connections are good shape, vacuum is very important on these old gals, 2nd reason, injectors, have they been checked, cleaned?

[rocky raccoon]

Agree with MP. Sounds vacuum related.

[supercanuck]

Thanks for the feedback.

When you say check the vacuum, is the a certain area or vacuum system that needs to be checked, or could a leak anywhere in the vacuum system of the entire car contribute to this problem?

[230/8]

Certainly you should check the vacuum lines, but also do a check on the plugs. It is easy to foul one and have it give a ragged idle. There is one on mine that is quick to foul during cold starts so I keep an extra plug in the tool kit.

230/8

[supercanuck]

By plugs, you mean spark plugs, right?

[rocky raccoon]

I assume your 450SL has an "economy" gauge as do the later models. If you have such a gauge and it is not fully pegged to the left with the engine idling, that is a sure indication of a big vacuum leak.

A vacuum leak anywhere (depending on severity) can cause driveability problems. By all means look at your spark plugs but if they all look good, I'm afraid you have to start chasing a vacuum leak. Inspect your vacuum hoses and connectors one at a time starting from your intake manifold vacuum source. Be methodical so you can isolate the problem. If you find one rotten rubber vacuum connector, change them all. Your car is 28 years old and I would expect the vacuum connectors to have reached the end of their useful life due to the oil and high temp environment under the hood.

[supercanuck]

Rocky, what is the economy gauge?

So a couple of weeks ago I changed out my plugs and wires, but I didn't notice it getting any better. I've also noticed that the car doesn't have the power it used to have. For example, I was going up a hill today (it was a steep hill, but nothing to write home about), and I had the pedal to the metal and it just kind of crept up the hill.

On a flat highway, it will get going to speed eventually, but still seems to be lagging.

[meltedpanda]

is your timing set? injectors serviced? trigger point plugs cleaned?

[rocky raccoon]

I looked at some 1980 450SL photos on ebay and found that your car does not have an economy gauge. Sorry about that. You have to learn to ignore me like my wife does.

By the way, not having one does not make your problem any less vacuum related. Sound like it to me.

[supercanuck]

Panda,

I'm not sure, probably not, and probably not

Are these things I can do at home pretty easily, or will it require a visit to my mechanic?

[supercanuck]

Alright guys, I was out looking around under the hood, and ran across something that I'm thinking may explain some of my symptoms. Take a look at the attached picture...I found pieces of a blue/gold vacuum line lying next to the air filter, and then I found what looks like to be the other end of where that line used to connect.

a) Can you tell me where this vacuum line is supposed to go to?
b) Will this explain a lot of what I've been seeing going wrong with the car?
c) Is it bad for me to drive the car like this until I can order a new vac line?

Thanks for your help!

[supercanuck]

Ok, so I'm starting to freak out a little bit about what may be going on with my car. It seems like everyone has their own idea/opinion about what may be causing the problems, and to be honest, it's starting to feel extremely overwhelming.

Let me recap the symptoms and things I've noticed:

• The car seems to be running pretty sluggish sometimes and doesn't seem to get up and go like it used to. It seems to hesitate sometimes on acceleration
• The car is shaking more while in idle than it used to
• I've also noticed that there is white smoke coming out of my exhaust. It's not happening all of the time, but mostly when I start it up and when I accelerate
• I changed out my plugs, wires, and distributor cap a couple of weeks ago
• The coolant I have is a generic green kind

I'm waiting to get a gauge to test the fuel pressure, and I am trying to get an appointment to have the cooling system pressure tested ASAP, but besides that, I really don't know what direction to go or what to look for/test first.

With all of that information, does anyone have any thoughts/suggestions?

Thanks!

[rocky raccoon]

Find a piece of small tubing (plastic works o.k. temporarily) and fit the two pieces of vacuum line together. I think you will find it will do wonders for your driveability issues.

Your symptoms still sound like massive vacuum leak problems.

[meltedpanda]

agree, fix those lines.
You really need to check the timing, and clean the trigger points
White smoke at start up could also be vacuumm related
I would not worry about fuel pressure until you do the basics
Cooling system would not cause these problems unless its empty!
Green Fluid is not good but not the cause of any of these issues