hesitation at normal speeds

[clickdoc]

i have been scouring the forums for help -- i have a 90 300zx na with hesitation -- most of all the probs that are usually listed have been replaced - almost new everything including injectors, o2 sensors, maf, etc -- one of the posts that replied to my query in 300zx forum mentioned that it could be the pcv valves ?? i also read that it could be a PCV hose leak ?? my car seems to run better when cold and hesitate or stall before 3500 rpm -- i will drive but you have to stay in it -- also stumbles after letting off the acceleration ?? what do you think ?? thanks
Modified by clickdoc at 9:50 AM 3/20/2007

[clickdoc]

sorry

i just read the part about full description of car :

the hesitation is happening in a 1990 nissan 300zx non-turbo

thanks

[clickdoc]

i jsut emailed the previous owner -- a really sharp guy -- a mechanical engineer no less -- he replaced the hoses underneath the plenum less than a year ago and replaced the PCV valves and cleaned the EGR ports -- PCV valves have a longer life than that -- don't they ??

thanks

[clickdoc]

well another update -- not PCV valves or hoses -- talked to previous owner -- new within the last year with all new hoses -- looked at the factory manual codes listed here http://zhome.com/ZCMnL/PICS/he....html -- it looks lilke i should have it narrowed down to three things -- because in addition to hesitation i also have surging -- the factory lists: 1. ECU 2. EGR 3. o2 sensors which are new - but previously i noted one of the wires was touching the headercan't wait to go in today and have it checked ~!

thanks

[wrenched_1]

have you checked your coolant temp sensor? could cause the same problems.

[clickdoc]

so i tried to go and get a diagnostic done yesterday -- they wanted me to schedule two weeks from now for a #$%&*ing 10 min diagnostic -- went to another place and said they would do it but based on the fact that the wire had been touching the header it was most suredly cooked and it would need to be replaced -- a nice guy -- they couldn't do the work because they can't get my car on their lifts -- so i am headed back to ultimatez so they can fix their own work !

[clickdoc]

ok guys

the final verdict -- it was the o2 sensor -- just had them replaced less than a year ago -- so here is the question for the professional -- if the o2 sensor wire was sitting on the header -- but did not burn through the wire -- could it still cause the o2 sensor to go bad ??

it is running great now !

[clickdoc]

hey guys -- are there really some online mechanics in thisforum ?? i have been trying to get a question answered by a professional -- anyway short story -- had headers and new o2 sensors put on several months ago -- had hesitation before -- that fixed the problem -- then it returned -- got to looking and the o2 sensors wire was sitting on the header -- anyway -- took it back out to get it replaced after running the diagnostic -- it was the o2 sensor but the wire was not totally burn through to be visible -- could the increased heat still cause the sensor to go bad ?? the o2 sensor was only about 6 mos old -- they originally going to charge me for the sensor but i talked them out of it -- what do you think ??