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Old 03-25-2012, 05:16 AM
mercmad6.3 mercmad6.3 is offline
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Join Date: Jun 2004
Location: brisbane,Qld.Australia
Posts: 2,062
Because it a MFI engine and you say the throttle butterfly was adjusted ,I suggest you go back to the beghinning and start with a correct tune up. Firstly, the injection is the LAST thing to be touched.
Start with a cold engine.
1/ remove the plugs inspect them and take a note of the color of each one.
2/ do a leak down test .NOT a compression check.
3/ adjust the tappets and check the timing chain condition..Replace the chain if the wear equates to more than 5 degrees of crank rotation.
4/ run a test on each plug lead to check for high resistance. Replace the terminals NOT the leads and if it has silicone carbon string leads ,throw them in the garbage bin and use Correct mercedes /Bosch parts.
5/ Check the distributor .Overhaul as per necessary. Replace the points with a pertronix.
6/ check the rotor arm resistance.
Check the fuel pump pressure (14PSi) and flow rate at the cold start valve (1 liter per 30Secs)
7/ Set the distributor timing to specs at cranking speed.
8/ replace all Worn throttle linkage ball ends.
9/ clse the throttle butterfly and set it so that it closed tight and can be felt to "bite" when Opened.
10/ The rod that goes across the cam cover must be set so that with the throttle closed,the ball end for the link rod must in line with the holwe in the raised casting on the manifold ( normally a tool is passed through this hole to fit against the linkage.
11/ make sure the oil level in the MFI pump is at the correct level (too much and the car will be sluggish) .
12/ make sure the lever is against the idle stop and fity the up rod to the lever and the cross rod. it must fit without moving either the lever or the cross rod,adjust it's length to tget it right.
13/ Move the linkage through it's arc, both the injection pump and the throttle lever must go from dead idle to full throttle and rest against the stops together.
IF NOT, YOU GET EITHER TOO LEAN OR TOO RICH RUNNING. IT IS VITALLY IMPORTANT THAT STEPS 9 THROUGH 13 ARE FOLLOWED RELIGIOUSLY.
14/ Remove the air filter on the MFI and start the engine. leave it to idle. It must be idling faster than normal .
As the enginer warms ,the rubber hoses running to the MFI must be hot.
If not check for blockages.
As the engine idles and it reaches 80C on the gauge the idle speed should slow down . ZFeel the port where the MFI aircleaner fits, if there is suction and the engine speed is still fast,the thermo is fualty.
(Note, the engine thermostat needs to be perfect)
15/ do a CO check on the exhaust at hot idle. it must be 2-5%. Any less and it's too lean.
To enrich or lean out the engine at idle, STOP the engine and turn the thumb screw on the end of the pump clockwise to rich ,anticlockwise to lean but never more than three clicks in either direction and ALWAYS on a hot engine.
16/ Check the two way solenoid on the trans .
17/ Adjust idle speed by turning the airbypass screw. open the screw more and you will need to enrich the mixture at the pump by one click.and to slow down viceversa. If turning the screw makes no difference ,the intake has either a faulty thermo on the MFI or an air leak (check power booster on brakes)
18/ turn off the engine, turn on the ignition .
open the throttle slowly, a click must be heard from the transmission as the throttle is moved off the closed position (about 1mm off the stop) .
Adjust the throttle switch until it works correctly.
18/ touch the acelerator pedal, as it moved slightly,a click must be heard from the trans, there is a switch on the rear of the pedal and this MUST work.
Finally , push the acelerator to the kick down and you should hear click as the trans solenoid click in the other direction .
If you cannot get the trans solenoid to clicj=k,it must be rectified otherwise the trans will never work correctly.

When driving, you must take your foot right off the acelrater when stopped in gear. If you leave your foot on the pedal , the trans effectly stays in gear and will be trying to drive the car. The throttle switch activates a oil pressure valve in the trans and releases the pressure from the fluid flywheel (it's not a torque convertor,thus no stall speed and it's constantly driving) when the acelreator is released.
If the engine is slowing when in drive and all of the above is OK,then set the idle speed solenoid on the intake manifold . When in gear ,the solenoid is activated when the pedal is released ,and it opens the throttle slightly . By holding your foot on the pedal you making the trans drive the car.
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