Really CONFUSED AND SICK OF TROUBLE SHOOTING<-----

[figo_madrid04]

Ok guys, hope this finds everyone in the best of health and spirit.
Ive finished my valve train rebuild and driving the car very cautiously until it gets passed 800-1000 miles

Ive got a couple of concerns, when my car is at idle at a light or somthing the oil pressure drops to low, its goes down to about 15-20 psi, i know this becuase i changed the oil and put in fully synthetic 0w40 to keep the pressure up, and then i hooked it up to a manual oil pressure gauge from the oil pressure sensor.
So my oil pressure is too low and this is dangerous for the top end of my valve cover, because i could hear a knocking noise when the oil pressure drops lower 10 psi. Btw is got a nismo preformance oil pump so its not the pump for sure and its not the gauge cause that works fine, i dont know what else it could be ????? or what else to do

another problem that i encounter is when the car is cold or when i dont let it warm up properly or just sometimes when i start it, it idles at like 2200 and doesn't drop in rpm even after it has warmed up and when i start to drive the turbo's will spool up fine but the car starts to choke and doesn't accellerate at all....... i dont know what the problem is there either, ive already changed plugs, coil boots i dont know what else to look for or what else to do.... what i normally end up doing is turning the car off and start it up again and hope the idle returns to normal then the car runs fine....

HERE is a brain teaser for all you crazy smart Z lovers......
any help is appreciated i really just want to get my car running well and have it realiable so i can drive it around the east coast this summer...

again thanks guys for any help

[figo_madrid04]

wow , where are all the smart a$$ Z ppl, id atleast expect some ppl to admit thy dont know ???????

[DeleriousZ]

your oil pressure is fine i believe... i've heard they go down to like 10 psi on hot idle...

second problem is a sensor of somekind, no time to think now, will answer later

[barkercustoms]

0w-40 wow i would not run that its like running water in your motor, as far as the oil press being to low 15-20 psi is fine too low is below 10. too much oil press is bad too, oil lubes and cools, whens its moving to fast it doesnt help to cool the motor off and will start to heat the motor as well. 15-20psi idle 50-60 psi driving is good

[barkercustoms]

o yea thick oil will help the top end out too. this way when you cold start the motor there will be a little bit of oil in the top end still

[DeleriousZ]

0w-40 is fine, i run 0w-50 full synthetic in my 88.... the higher the last number, the better it handles high temperatures.... but if you think the oil is breaking down you can always add some lucas oil something or other (on the display stands at your local napa) and that should thicken it up a bit...

as for the second problem, it sounds most definitely like a sensor issue... buggered chts? i know that causes a lot of problems with the z31's...

is there any sort of smoke coming out of the exhaust when it chokes out like that? could be richening out during acceleration or something...

[Joe300Z31]

yeah actually my 87 n/a does that too... i gotta warm her up 1st and i'm also running synthetic. i think you're on the right track cuz i have a sensor light on and have no idea what it is. when i start it...the idle goes up like u said and when i give if gas while its warming up, it sounds like i'm getting a bad burn. my muffler is rusted out and all u hear is some kinda popping and crackling. after its warmed up i have no problems. dunno if i added to the confusion or not and i'm not sure if this
is the same problem as his.

[ExTrEmEDrIfT]

run ecu codes....


joe the sensor light im sure thats the o2 sensor the panel under the steering column theres a plug that says to unplug at like 70,000 miles or something weird but if you unplug t it will shut off the light .. mine was aready unplugged when i got my 86t and it ran fine...


dont make sense you have to unplug it though i never really read into it

[Joe300Z31]

i've run ecu codes b4 and the only probelm that came up the time i ran them
was a low idle so i really don't know. when i put in it gear and ease on the gas and ease off the clutch it seems i'm getting spurts of power than
a constant flow of power like i should be getting. that why i said i'm getting a bad burn or certain cylinders aren't firing or somethin. i did a basic tune up when i got the car but i don't know if u have any ideas.

[ExTrEmEDrIfT]

how did the cap and rotor look? could also be the coil -- did you ohm it out??

[Joe300Z31]

cap and rotor i replaced. its probably a bad coil...would make sense.

[DeleriousZ]

joe i recommend taking the question to 88hybrid.com they'll be able to help you out without a doubt.... my guess is the CHTS because they're Always seeming to go bad on these cars... or something along those lines... maybe fuel temperature sensor...

[figo_madrid04]

so i guess my oil pressure is fine........ but how do i explain some of the sounds that come from engine...... some come and go, some go when the oil pressure rises.... some only come when the car is cold and is warming up .....

i have no idea what the problem can be....


does anyone think that it can be some type of electrical problem ....
when the idle is at normal , the battery light somes on very slightly
and the car smells like gas out the back, im there isn't the right amount of spark or some shortage and there is a misfire and the engine boggs down and so that cylinder doesn't combust properly.......

ive changed the boots and the plugs , but how often do the coils need to be changed and also do i need diffrent coil assembly if im running the cold spark plugs???

thanks guys

[DeleriousZ]

do you have a voltmeter in the car? that might be a good thing to check... could be your battery is dead/dying and or your alternator is on its way out, or the belt is just loose...