New to forum...same old probems

I did a search on the forum and didnt find the information I was seeking so I'm looking for a little help...


Make a long story short, I got sold a lemon and its a 190E. It has a very rough idle and no acceleration at start. It runs fine on highway, so it seems. I would like to change out the fuel filter but thought I'd make a post here and see if there were any helpful hints in doing so before I got started...first thing I'd like to know is where its at and if I need to take the whole car apart to get to it.

Another of the long list of items that I would like to work on is the belt squeeling/chirping when the ac is on. I checked the belt and it seems loose but I'm not sure if you can tighten these manually or if some type of auto tightener wheel is shot. Any help would be great.

Tried to go online and purchase a subscription to Chiltons but they dont have MB available online. Anyone in Houston area know where to get a hard copy locally, pls share!

Great info on this forum and glad to be a member now!

[psfred]

You didn't list the year of your 190e, so I will have to make some guesses as to the source of your problem.

If it had KE-Jetronic injection (cis -- no wires to the injectors, just solid metal lines from the fuel distributor under the air filter), you most likely have the idle/performace problems common to the 300e of similar age. These are OVP relay, idle mixture at the upper or lower limit of computer feedback control, or a bad, stuck, or leaking idle control valve.

The hoses on the idle control valve will cause air leaks, and you symptoms are just like that -- rough idle, random stalling while stopping, particularly on a hard stop, and terrible throttle lag -- you stand on in and NOTHING happens for several seconds, then the car takes off. Sometimes is will also stall. This is due to the large air leak at the idle control valve.

Other vacuum leaks will cause trouble, too, so check all the vac lines -- there is one to the computer on the fender, a transmission line, and lines to the EGR and some thermovalves. I'd replace all of them, they are likely dead. If the tranny shifts late and hard, this is more evidence of vac leaks. The only part you need to replace is the short rubber ends, the hard plastic will be OK unless broken, in which case a short rubber bit will patch it.

The OVP relay provides power for the electrohydraulic actuator on the back of the fuel distributor, and if it is bad, the EHA goes on and off randomly, doing strange things to the fuel mixture. Causes rough idle and throttle lag, sometimes.

If the idle speed control valve sticks, in will cause rough idle as it fails to respond to small changes in idle speed, then "jumps" and sticks again. It is closed above 1000 rpm or so with the throttle closed, and if it sticks shut, the engine will die it if doesn't jump open soon enough. Cure is to take it off and flush it well with carb cleaner, perferably while running the motor back and forth, until it works properly and there is no more discoloroation of the carb cleaner.

There are many posts on idle/preformance problems on 300Es -- your engine and control systems are similar.

Peter

Sorry about lack of info but its an '87.

Sorry to sound ignorant about these cars but I'm learning. How am I to tell if I have a vac leak?

[psfred]

A big leak will hiss, usually loud enough for you to hear it if you take a piece of 1/4" ID hose and use it like a stethoscope. You can also tell if a rubber hose is leaking by pulling it off and putting your finger over the fitting -- if the idle changes, the hose was leaking.

The rubber connectors must fit tightly enough that the hose won't slide out, and if they are no longer pliable, they leak. Plan on replacing all of them. If the rubber parts rattles around on the barb (this especially applies to the idle control valve), it is leaking since it isn't sqeezing down any more.

Leaking actuators, transmission modulators, etc must be checked with a MitiVac hand pump, about $30 at any auto parts store. This is a hand gadget with a hand powered vacuum pump, guage, and a bundle of adapters. It will pull, slowly, a petty good vacuum on any system on the car. Some have tanks, and will take a while, but the MitiVac will get them down to 15" or so mercury with some pumping. If you cannot, for instance, get the climate control to hold vac by pumping at the green line in the engine compartment (disconnect from the engine and connect the mitivac instead), you have a leak and will have to check inside the car.

Peter

PSfred,

Funny thing after you made your first reply, I went and listened to the engine compartment just to see if I could hear anything (common sense) and sure enough I found a boot that was dry rotted (split down the seem) and had just a little bit of hissing. The little unit it connected to, connects to another hose and it slides off and on very easily. (Now from your second post I'm sure it leaks as well). Well, my next question are what are these lines and what is it connected to? First off, the item in question is to the left of the fuse box assembly. It has 3 inputs or outputs. A green hose (cant remember tracer) and a red hose with a grey tracer come in from the top end. Then the piece itself plugs into a black hose. The red hose/grey tracer goes down toward the engine compartment ( running parallel with the windshield) somewhere. I looked but didn't see where it emerges. The green hose seems to connect to a piece going towards the cabin of the vehicle.

My next observation was after pulling a plug out...I have ngk plugs that have some carbon build-up on them. My question is how sensitive is the vehicle to the proper plug brand being used?

Also, the squeeling/chirping I mention when the vehicle runs goes away completely if the A/C is not running. It still sputter a little then starts to go but not quite as bad when the A/C is running.

There are new plug wires, distributor cap and couple other items in the engine compartment that look brand new. Engine looks like it was rebuilt judging by the new looking gasket material in different places.

I very much appreciate all the feedback you have given...Thanks.

www.************************ has a 190E Haynes manual for 190E 1984-1988. Part number 99-096 @ $15.95. Also, you can get their 190E parts catalog free (very comprehensive and loaded with exploded illustrations/part numbers/descriptions).

Good luck and welcome!

Brian16V

[psfred]

Ha, you found your vacuum leak! The green plastic hose is the vac supply for the Climate Control. The red/gray is for something else (I only have two gas engines, the rest are diesel and they are different).

You will have to get anything but simple straight bits of rubber hose from a dealer or good independent MB mechanic, they aren't expensive, but you wil have trouble finding the y and T connectors anyplace else.

Check the rubber hose bits for all the hard plastic lines, there are several (some go to temp sensors, some to valves, etc) especially those on the intake manifold. They are all in the same condition as the one you found, and replacing them will make a big difference.

The black line is a vent line, usually, and, and can be ignored.

Carbon fouling of the plugs indicates rich mixture or ignition problems. The ignition is probably OK -- new cap, rotor, etc, but you may want to check condition of the wires! If not installed properly, or not removed properly, they will be broken inside and not working properly, and this will cause bad running, fouled plugs, and eventually a roasted catalytic converter. Don't play with them with the engine running, as the voltage can kill you if they are leaking badly.

NKG is a perfectly good plug, but check that the heat range is correct. Also, make sure this is carbon and not oil residue, as worn out valve guide seals will cause fouling and misfire, resulting in plugs with black deposits over brown/gray crud.

A leaking cold start valve will cause rough idle, throttle lag, and rich idle, too, from unwanted fuel running into the manifold.

The bad news is that a bad fuel distributor can make the car run rich, and the only cure is a rather expensive replacement, you cannot fix them.

Peter