hard cold start popping hesitation
 

89 300ce,i replaced both fuel pumps per techs order of low fuel pressure,replaced fuel filter,i replaced the ovp,i also replaced the eha with a used one,the car still needs an 02 sensor.i had the air/fuel ratio recalibrated.do you think i purchased a defective eha? im going to check into the coolant temp sensor,does anyone know wich coolant sensor is the one that controls air fuel,where is it located? thanks for all your help guys.the car starts ruff when cold,needs to warm up 3-5 mins,or will hesitate pop,buck,misfire,even when full warmed up,car lacks full power on highway in passing gear,it will not shift unless i lift foot off accelerator,also i noticed while it revs,the cars engine gains more power as i lift my foot off the accelerator.

What is the condition of all the electrical items such as plugs, wires and cap & rotor? Who adjusted the fuel mixture? I wouldn't bother with a used EHA. They do wear out internally over time. What was wrong with the old one? You could try building yourself a code reader and checking for codes. A search will reveal more information on how to do this.

the wireharness is in like new condition,the connector ends are all shiny silver,the mercedes mechanic adjusted the air/fuel/after i replace the o2 and it still acts up,i will check into the coolant senser,keep in mind e verything is all original on this engine,the plugs/wires look great,i havent pulled the cap yet to look at the rotor,the wires and plugs are 21 yrs old,you think i should give her a fulll tune up next?i.e. plugs wires cap rotot? i did regap the plus and it helped a bit,but nothing to brag about.

Original plugs and wires? Doesn't seem likely, but if that's so, you got your nickle's worth on those, and getting a fresh set would be a good idea. It sounds as though a regular maintenance program was never followed on this car, so I would begin that now. That means plugs, wires, cap & rotor, regulator brushes, all filters, all fluids, all vacuum lines. At least then, any further driveability issues can more readily be diagnosed and pinpointed. You may have needed EHA, O2, duty cycle adjustments and all the rest, but it sure seems like your tech came at it backwards.

yes i think the tech did,look backwards,what are regulator brushes?,im going to change the cap and rotor,the s plugs look great.the wires are very clean in like new cond.there still crimp numbered #1 and #6.ive inspected all wire boots and they appear brand new,but everything has the mercedes emblem on it,or says bilstien.several hard plastic vacum lines were broken so i had to fix them,the line to the fuel fressure regulator was broken,and the line ncoming out of the air breather was broken,several were disconnected,i need my tech to check all vacum lines for leaks and proper line up,my economy guage sits about 3/16" to the right at idle,then in gear sits just off the red line.