Cruise control I have a 92 Merc Benz 190e, auto and the cruise slows to cuts out, if I hold the accel, then it speeds up without kicking out, what do you think?

step 1
Remove the left sound insulator
step 2
the stop switch is here, way way up top
use flash light to see it.
it is there.
top of pedal it is there. SM books step1.

buy the service manual.?
if the switch ever sticks on , cruise ENDS
it is a NO, switch normally open contarts
no calibration is stated so its PnP

It is HVAC 1fuse #39 in the rear fuse block ,this powers the on/off switch for cruise control ! Fuse Block - Rear Beneath the left rear seat. What engine does it have ? 4.2 L or 5.3 l There is no vacuum involved in the operation of the cruise control ! Your vehicle has electronic throttle control .
Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at vehicle speeds above 40 km/h (25 mph). Steep grades may cause variations in the selected vehicle speeds.
The following are the main components of the Cruise Control System:
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The powertrain control module (PCM)

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The On/Off switch

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The Resume/Accel switch

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The Set/Coast switch

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The TCC brake switch

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The stop lamp switch

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The throttle actuator control (TAC) motor

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The vehicle speed sensor

Cruise Control Engaged
The cruise control system will engage and adjust the vehicle speed based on the activation of the following cruise control switches:
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On/Off

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Resume/Accel.

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Set/Coast

The cruise control switches are located on the multifunction/turn signal lever.
The powertrain control module (PCM) monitors the signal circuits of the cruise control switches in order to determine when to capture and maintain the selected vehicle speed. The PCM uses the throttle actuator control (TAC) module motor in order to control the vehicle speed. For further information on the TAC System, refer to Throttle Actuator Control (TAC) System Description in Engine Controls - 4.2 L.
Ignition positive voltage is supplied from the 10 ampere HVAC 1 fuse to the cruise control switch via the ignition 3 voltage circuit. When the normally open cruise control On/Off switch is turned On, the switch closes and the PCM detects a high signal voltage on the cruise control on switch signal circuit. When the normally open Set/Coast switch is pressed, the switch closes and the PCM detects a high signal voltage on the cruise control set/coast switch signal circuit. To engage the cruise control system, turn the On/Off switch On and momentarily press the Set/Coast switch. The PCM will confirm that the cruise control enable criteria has been achieved. The PCM will engage the cruise control system and record the selected vehicle speed. The PCM sends a class 2 message to the instrument panel cluster in order to illuminate the cruise control indicator. Pressing the accelerator pedal, while the cruise control system is engaged, will allow the driver to override the cruise control system in order to accelerate the vehicle beyond the current set vehicle speed. When the accelerator pedal is released, the vehicle will decelerate and resume the current set vehicle speed. The driver can also override the current set vehicle speed via the Set/Coast switch and the Resume/Accel switch. When the cruise control system is engaged, pressing and holding the Set/Coast switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating the cruise control system. When the Set/Coast switch is released, the PCM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily pressing the Set/Coast switch will allow the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the Set/Coast is momentarily pressed, with a minimum vehicle speed of 37 km/h (23 mph). When the normally open Resume/Accel switch is activated, the switch closes and the PCM detects a high signal voltage on the cruise control resume/accel switch signal circuit. Activating and holding the Resume/Accel switch, when the cruise control system is engaged, will allow the vehicle to accelerate to a greater vehicle speed than the current set vehicle speed. When the Resume/Accel switch is released, the PCM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily activating the Resume/Accel switch will allow the vehicle to accelerate at 1.6 km/h (1 mph) increments for each time that the Resume/Accel switch is momentarily activated, with the maximum acceleration total of 16 km/h (10 mph) over the current set vehicle speed . Momentarily activating the Resume/Accel switch, after the cruise control system has been disengaged by pressing the brake pedal, will recall the previous set vehicle speed that is recorded in the PCM.

cruise controls are controlled by several units
VSS or road speed sensor, clutch and brake sensors , engine speed (tacho) and the on/off switch
cruise controls will disengage automatically if the road speed is too slow ( higher for manuals than autos ) so if the road speed is below around 20mph it may not engage at all as the VSS says it is too slow for the engine rpms
check all sensors for adjustment

Bummer deal! This may be a way to tell you some tail lights are burnt out. Some cruise controls have a fuse in a second location.
The fuse is not in right or is blown. Check with a new fuse. Hope this helps. ...gc http://www.auto-tune-up-and-repair-options.com/

not being informed if it is auto or manual, here are some of the items that control the cruise control
brake pedal sensor ,
clutch pedal sensor,
vehicle speed sensor
engine ignition control module , tacho ,
vehicle speed --will disconnect if the road speed is below setting minimum speed
ratio changing
bad cruise control switch
wiring and connections
ecm problems
problem cruise control module

i would start by checking the idle air control valve. it may be called something else on a merc but basically it its a solenoid that controls the amount of air entering the throttlebody when at idle they tend to get sticky and slow when they are on there way out. hope that helps, i dont know if it is the answer but it is certainly worth looking at. let me know how you go

Serpentine Belt Diagram - 87 Merc 190E

Go to the following web site below (copy and paste the web address below into your browser)

http://www.daycoproducts.com/daycoweb.nsf/cf652a4feb630ad0862571a4005ae40c/a866a821123f887c862571a5006988df!OpenDocument

There are 2 PDF documents to open - above the photo on the site.

The first - the Routing Guide - shows the reference for the belt diagram (1987 MERC 190E) which is 6-2 on page 92 of the Guide.
The second PDF shows the belt diagram for 6-2.

Hope this helps.
Cheers
Sean
Voluntary contributor.

i would suggest it could be the fuel filter hope this helps regards Jim

please check whether you put "W"(Winter mode) instead of "S" .....

have you had the transmission flushed? it seems to be caught in a limbo. where the calibration of the speedo and the transmission are not compatable. Now as wierd as that seems it happens usally like when going up a hill if you have a manual trans. and cruise locked in. it cant hold that speed and moves to a different speed if you dont down shift. Or perhaps your cruise control cable is slipping. is it vacume over mechanical? pop the hood and make sure all your hoses to cruise control are tight and no leaks.