FAO: Oscar - Merc 350SE acceleration related

[BJ]

Hi!

I just watched your movie clips in the gallery section with your 0-100km/h runs in your 350SE. Your car farks off, that's for sure! 

My car can do a similar run like that, but then I have to start in either L or S because it doesn't hold the gears in D long enough.

Eg. No matter how much you floor it from standstill in D, it changes up at about 3000rpm or so anyways, but holds the next gear until about 4500rpm or so which helps.

My car has been out of use for the past 2 years, and I have only been driving it around for about a month now. I serviced it immediately after I got it. Replaced oil, filters, plugs, etc. and it's a lot better now. When I got it, it wouldn't even rev over 3000rpm when in park!

What can I do? Should the engine be tuned? Should I have something adjusted on the gearbox?

Your thoughts greatly appreciated.
BJ

Edited to add: O yes, it also doesn't kick down when floored at speed. The only time it will kick down is under 60km/h. Above that, nothing happens when you floor it.

[oscar]

Haha, I had to watch them again, I just love the sound.  I had 7 runs recorded and I was around 10 seconds each time.  Don't think I broke 10.
I drive with two feet a lot so what I did in the clips was stand on the brake whilst in gear and floor it, then let the brakes go.  That occurs when you see the camera lurch backwards.

Now to your car - you'll have k-jetronic mechanical fuel injection, my car's a '73 with d-jetronic electronic injection.  There's a couple of tricks with d-jet  like messing with the CO screw and Manifold Pressure Sensor but I'm not going to play with them and you wont have them.   I'm not sure what you could do to k-jet.  I just don't know enough about k-jet servicing but someone else fluent in k-jet will be able to help and suggest what to change.

Regarding the kickdown, there's a round button on the firewall sticking thru your floor mat behind your accelerator.  It's a vacuum operated kickdown switch and operates when you floor the accelerator.  The accelerator rod supporting the pedal pushes this button in and kicks the tranny down a gear.  Check where this black round switch is behind the accelerator, then next time you're driving and after it's upshifted to 3rd or 2nd, stand on the accelerator so you contact the switch.  It should kickdown.  If it doesn't give it a little more pressure.  At the moment you may not be reaching it.
Another possibility is the switch is buggered or the vacuum lines are disconnected or cracked.  I haven't had problems with it so if it is stuffed, I know there's others here that has dealt with them in the past.

Lastly, adjust your timing and advance it.  Go in increments but no more then 10o BTDC.  You might start hearing pinging after that especially when you accelerate.  I think you said the timing jumps around a bit so look for where the marks hang around the most.  See how advanced you can go before pinging.  Adjust on a warm engine and adjust idle to around 750rpm afterwards.  My ignition was around TDC or on the retard side for those runs.  I've since advanced the ignition to about 5o BTDC but haven't been out again.  There's definitely more power from advancing the timing.

Actually, one last thing.  Regarding the auto, make sure you check the level after going for a drive and manually selecting all gears so  the AT and engine warm up to operating temp.  Don't turn the engine off, check the level whilst engine is running.

That's all I can think of for now.  Good luck.

[WGB]

If the 350 has the same set-up as the 450 you can adjust the kickdown rod which is connected to the throttle linkage at the back of the manifold.

From memory moving the rod forward makes it kickdown quicker and holds the gear for longer and moving it back makes it change up quicker,

Remove the aircleaner and look at the rear of the manifold where the throttle linkage is visible - there is a curved rod disappearing down to the transmission. It is held in a spring clip and is easily adjustable - just do little bits at a time and then try it out.

Bill

[BJ]

Thanx Oscar and Bill.

Will check out the things you mentioned.

I know of the button under the accelerator pedal and I do press it firmly, but no kick down over 60km/h. Since you mentioned that it's vacuum operated, my vacuum seems to be a bit problematic since my central locking and cruise control doesn't work. Could this have something to do with the lack of kick down?

[oscar]

Possibly.  I don't know exactly how the kickdown switch is plumbed but the faulty kickdown, troublesome central locking and non working cruise control, could very well be three seperate issues.  If you could block vac off from all other lines other than the vac switch, you may be able to check its operation once and for all.  But I don't know how the switch is connected.

[WGB]

The rod on the throttle linkage only controls part throttle kick-down on my 450 - as fas as I know this is separate to full throttle kick-down .

So you may have two problems.

I would fix that vacuum leak - it's probably only one connector and if all systems are affected it is probably very early in the system - I would check your manifold connection.

The hand-book gives a good description and diagnostic flow chart of how to diagnose problems.

Bill

[BJ]

The rod on the throttle linkage only controls part throttle kick-down on my 450 - as fas as I know this is separate to full throttle kick-down .

So you may have two problems.

I would fix that vacuum leak - it's probably only one connector and if all systems are affected it is probably very early in the system - I would check your manifold connection.

The hand-book gives a good description and diagnostic flow chart of how to diagnose problems.

Bill

Probably stupid question, but where can I find said "handbook"?

[oscar]

http://handbook.w116.org/ Then click on the link towards the bottom of the page.


I had a look at the handbook last night but only in the vacuum section regarding central locking.  Both control pushrod that WGB talks about and the kickdown switch is mentioned in my Haynes manual, but I couldn't find anything about the switch in the Handbook.  The Control Pushrod may be in there too but I couldn't find it.

[BJ]

http://handbook.w116.org/ Then click on the link towards the bottom of the page.


I had a look at the handbook last night but only in the vacuum section regarding central locking.  Both control pushrod that WGB talks about and the kickdown switch is mentioned in my Haynes manual, but I couldn't find anything about the switch in the Handbook.  The Control Pushrod may be in there too but I couldn't find it.

Which model and year should I look at since a 77 350SE isn't listed, or would any of them suffice?

[BJ]

Ok so I found the part on the central locking vacuum. I'm fairly certain I know where my problem is. There's a little pipe close to the aircleaner on top of the engine that's being held in position (sort of) with isolation tape. Think it needs to be reconnected properly.

I will take pics as soon as I can and let you guys know.

PS: Let's not kid ourselves here, my knowledge on these cars (or any for that matter) is pretty limited and everything I know, I've learnt in the past month since acquiring my car.

[WGB]

I know I have a diagnostic chart for the vacuum system and I thought it came from the Handbook.

I'll look tonight and if I can't find it I'll hunt for the pages I have and "PDF" them.

I think however that with all systems involved it is likely to be the main vacuum connection that is the problem.

You will have to take the aircleaner off the car (Three nuts and disconnect the pipe underneath) and you should see the rod that I am talking about as well as all the vacuum lines.
The main distribution system for vacuum goes from the engine into a vacuum tank in the ?driver's wing and then back to a collection of pipes next to the brake booster. Some of these connections have one way valves to isolate one system from the other. It is unlikely that all systems have failed individually - much more likely there is a leak in the main line that feeds the whole system.

The vacuum pipes and the control rod should all be visible with the aircleaner removed and in the same general area of about a foot at the rear of the engine on the driver's side - (unless the 350 has a different kickdown system)

Bill

[oscar]

Which model and year should I look at since a 77 350SE isn't listed, or would any of them suffice?

Sorry I forgot - Look at a 77 450sel, or a 76 450se.  Any 450 4.5L after and including 1976 will be virtually the same.