hesitation on cold start popping in plenum
 

i have an 89 300ce, replaced both fuel pumps with high flow fuel systems pumps,replaced the ovp,replaced fuel filter,had air fuel ratio calibrated,now i just need to replace the o2 sensor,car has to warm up for about 10 mins,or it will hesitate taking off popping in plenum,bucking then finally taking off and driving normal,but it still lacks full power,and when it down shifts it stays reving until i lift accelorator,does an o2 sensor cause this much issues with fuel,i was told from my mechanic all this would solve the issue,so i wonder if anyone thinks just the o2 sensor will solve this,thanks poeple.

The O2 sensor has no relevance to cold start operation, so a new sensor will not solve your cold start woes. What you describe is a lean condition that appears to be caused by a lack of cold start enrichment. Could be something as simple as an engine coolant temp sensor but my diagnosis is faulty mechanic.

well that is a new avenue i can check into,i know there is about 2 or 3 of them,so why not just replace them to,right.

Only one of the sensors is read by the engine control, have it tested and replace it if it is out of spec. Could be many other issues causing your problems. Temp sensor is an easy inexpensive and common fix and should be ruled out before further diagnosis.

Sounds to me like the EHA or coolant temp sensor at the back of the head. Remove the plug from the sensor and see if you notice any difference. If there is no difference (only noticeable when cold, warm has no difference connected or not) it may be wise to replace it..Not too expensive either.

could be a erratic OVP relay ,the cold start system depends on it .
mak

i will check into the temp sensor,the ovp is new,the eha is also new.thanks guys.