Very fast Idle, 5.0 in 1980 450 SLC (Euro)

[kip Foss]

Leewolf,

If you are going to buy more than a few aprts from the local MB dealer try to register yourself there as a restoration company or some such. I did this at my local MB dealer in Corpus Christi, Tx. and they matched the aftermarket people's prices very closely. Granted I had a very cooporative partsman, but all I did was show him the prices I could get my parts for from the cataloges and he said that with a dealer's discount he could match or beat them-and he did in most cases. It never hurts to ask.

[Damian]

Thanks for your info Deltacom.

Actually my contour hose does have a connection point for a vacum hose, but both are also blocked with small screws.

As for the vacum swith over valve where would I find that?

Some one has disconnected the positive feed to my A/C switch before I got the car, cant seem to find it either. So it never worked. So it may have something to do with it .



Many thanks for your help on this

Damian

[CamelotShadow]

Originally Posted by Damian

Thanks for your info Deltacom.

Actually my contour hose does have a connection point for a vacum hose, but both are also blocked with small screws.

As for the vacum swith over valve where would I find that?

Some one has disconnected the positive feed to my A/C switch before I got the car, cant seem to find it either. So it never worked. So it may have something to do with it .



Many thanks for your help on this

Damian

Mine came w a hose with 2 screws blocking the ports also.
I purchased a new part identical but with no open ports on top.

I have to wonder if mine was converted & didn't need the 2 vac lines or
buy the correct part & reinstall the 2 missing vac lines.

[Deltacom]

Damian,

The switch-over valve (change-over valve) on most 107 is located in the firewall just behind the air filter (in others is on the fender just below the washer reservoir). Since your A/C is not working you might as well disconnect the electric plug to the switchover valve to eliminate this possibility.

Your vehicle with the vacuum inlet in the contour hose indicates the vacuum-controlled pressure regulator is required. (without it the acceleration response is more sluguish and noticeable lack of performance at high revs.) to do away with this requirement this function is taken over by the pressure-step switch to activate the control unit in the lambda control wich it might not have been upgraded in your car.

See pic of the switch-over valve

[Leewolf]

This is the second time I've tried to send this message and the first time in several days that I've been able to use the forum. For some reason they decided my password was no good and I couldnt get to the right place to reset it. Anyway its fixed now i hope.
We reset the timing and the idle screw as you suggested. It runs a couple of orders of magnitude better. Not perfect, just a little cold natured and also a little rich. You can smell it in the exhaust.
I've taken it to the tranny shop for now. I felt we needed to make sure the linkages and tranny itself were functioning properly befor fine tuning of the engine. I hope you dont mind my keeping you informed, I am fust so very grateful for the help.
Thanks, Lee
ps see my new thread regarding the euro headlights i haveon this car.

[CamelotShadow]

Originally Posted by Deltacom

Damian,

The switch-over valve (change-over valve) on most 107 is located in the firewall just behind the air filter (in others is on the fender just below the washer reservoir). Since your A/C is not working you might as well disconnect the electric plug to the switchover valve to eliminate this possibility.

Your vehicle with the vacuum inlet in the contour hose indicates the vacuum-controlled pressure regulator is required. (without it the acceleration response is more sluguish and noticeable lack of performance at high revs.) to do away with this requirement this function is taken over by the pressure-step switch to activate the control unit in the lambda control wich it might not have been upgraded in your car.

See pic of the switch-over valve

Where would I find this?

My engine

[Damian]

Deltacom,

You are a wealth of knowledge arn't you.

I will have a look at these as soon as I get my car back from the painters, it in there getting a new trunk lid but on and getting the soft top cover panel tidyed up.

I may be getting a manual on this engine soon which could help me out to no end I'm sure, but at the moment I'm going by a generic k jet fuel injection book which doesn't mention all the fancy bit these cars have. like the pressure-step switch and the lambda control unit.

I wish when people played around with them they wouldn't remove thing that are required, just to get the job done.

Thanks to you i'm getting closer to fix it all back up

Thanks
Damian

[Leewolf]

The Aux Air Valve did exactly what you said it would. The Idle came down to about 1200 at cold start and works its way down to about 400-600 at 80C. I am however having some intermittant problems when starting warm or just-a-little-bit-warm. after sitting just a little bit it starts very rough and has to be rev'd a little to get it to not die and then it will idle and perform alright. BUT, after sitting awhile(say and hour or more but not cold) it can start very rough and then buck, backfire(a little), chug and will hardly get out of its own shadow. This is very similar to a problem I had with a GMC in which the distributer had been misinstalled. If I get it to a highway or long stretch I can get it running OK until I slow down to turn, it will die.
Incidently, I have the timing advanced about 13 degrees for performance. Could this in any way be contributing to the problem.
Also, this EURO 5.0 has 2 vacume connections from the WUC to the Aux valve hose. One comes from the bottom of the WUC and goes to a connection at the engine side of the Aux Air Valve(AAV). The other goes from the top of the WUC to a connection on the other side of the AAV. I cant tell from you picture if this is correct or not. Any thoughts on this would be appreciated.
Again. Thanks so very much for your help on the AAV, Lee

[Deltacom]

Lee,

It's clear that the initial problem of high revs was a defective AAV, so this problem is solved (its causes) or you are in the process of replacing the AAV.

There seems to be two additional problems from your post:- a) stalling due to low revs on load and b) hot-starting problem. It would seem to me that due to a defective AAV causing high revs it has masked these two other problems by compensation with high revs (costly in fuel) and there has been an attempt to compensate by adjusting the idle regulator screw (the nylon screw with a spring) and now that the AAV excessive air volume has been restored to normal (by blocking the AAV or replacing it) the idle adjusting is too low.

Low revs on load and timing advance have a knock-on effect on each other. I suggest to stabilize timing back to "0" (TDC) to eliminate this contributory factor to the two problems at hand for the time being (afterwards you can advance timing for performance but to no more than 5 degrees BTDC as over 5 degrees it has other repercussions at low revs). The timing back to "0" should be done with engine at operating temp and vacuum advance disconnected and blocked. Then start the engine and engage gear in "D". The idle revs should be adjusted to 500 RPM minimum in gear. (Your symptom of stalling when on a turn indicates de revs falls lower as the steering power pump adds to load when in gear and the engine can't cope).

With regards to problem b) there are a number of factors that can cause these symptoms, e.g.: Loss of Rest Pressure, improperly adjusted airflow sensor, sticking or binding control plunger, leaking injectors, leaking cold-start injector or shorted thermo-time switch, incorrect control pressure, defective fuel-pump check-valve, and others….
For each of these possible factors there are specific procedures for testing and verifying but at this stage I suggest you attend to sort first problem a) as you did (or are in the process of) with the AAV. Will assist you with problem b) once a) is out of the way and the reasons for this are that sorting problems out of sequence creates compensating "cheating" as in the case with the AAV and when the "cheat" is sorted out problems masked by the cheat become apparent.

[Leewolf]

I'll be able to get on this thing Monday. Please let me review.
1. AAV replaced, idle revs reduced to 1300 cold coming down to about 400-600 at 80C.
2. The AAV problem has most likely been masking some other problems that are now showing up, rough warm starting and chugging, etc on occasion and stalling on turns.
3. You recommend the following actions. reset timing to 0 TDC,
adjust idle (screw).
4. The list of other "possible" contributers is daunting to saythe least BUT will keep you informed of progress.
Thanks again, Lee