power vanishes....

[johnshop]

so i have made post's about this before, and i did everything everyone told me, and for some reason it keeps happening.

so, when i turn the car on, i have all the power available, but after 5 minutes or so the power literally vanishes. to get going i have to pretty much floor it and the revs build up slowly all the way to 3k then is picks up.


here is a rundown of what i've done so far:
no codes.

checked maf, cleaned it and reinstalled.

adjusted TPS, Note: closed throttle read .45, but WOT it was all over the place, is that normal?

relocated knock sensor
what i have not done:

check for coilpacks

check spark plugs

test for bad injectors.

fuel filter

is there anything else i should check for? besides doing a power balance test?

[twinturbozxtacy]

id check the cat possibly, and o2 sensors and no the tps is a precision sensor should not jump in a fixed position unless you have a bad ground or connection some where

[NolimitZ32]

Cant say for certain without actually doing the diagnosis myself but 95% its electrical, something is heating up, raising the resistance and putting out the wrong reading.

[johnshop]

Cant say for certain without actually doing the diagnosis myself but 95% its electrical, something is heating up, raising the resistance and putting out the wrong reading.

and that could be the tps, maf sensor and such?

maybe a cable routed wrongly or something in that general area?

i did have my plenum pulled when i just got the car to replace injectors. maybe the mechanic put the cables too close to a hear source?

[t.mcginley.jr]

So the loss of power only happens after the car is up to operating temp?

And just as a note, the TPS should be 0.45V closed throttle, between 4 and 5V at WOT, and it should steadily increase from 0.45 to 4-5V as you press down on the throttle.

[johnshop]

i remember it being at .45 every time no problem, but then it wouldn't keep a steady reading at WOT.

[NolimitZ32]

You have a closed loop fueling issue, the car goes from open loop to closed loop fueling once warmed up and starts using the sensor readings, the sensors it reads are the MAF, TPS, & O2s. one or more of those is malfunctioning or you have a vacuum leak elsewhere that you have not yet found. It also switches between open and closed loop base don the load and RPM which might explain why it runs better above 3k revs.

[johnshop]

yes only when is at temp, in fact when is cold i have to be careful with the throttle, the rear end loves to slide around when the car is cold.

some times to get it going too after not making a complete stop, i have to floor it, and then it thinks about it for a second and shoots like a rocket, but if i won't floor it, it just as slow as a prius...

what is a closed loop fueling issue? so when the car is cold, it does not uses sensor readings? im confused.


and is the're a more common spot for vacuum leaks? or it could be anywhere? would this diagram from tt help?

http://www.twinturbo.net/nissan/300zx/f ... agram.html

and it just might be a vacuum leak, when car is in park it revs high, but when i put it in drive, it goes back to normal... ( auto, OH THE SHAME ahah )

[NolimitZ32]

When the car is outside normal operating conditions (like before its warmed up) it uses the output from the TPS and matches it to a predetermined value in the fuel maps and sprays the predetermined value of fuel in. once it warms up it goes into closed loop where it uses readings from the MAF and O2s to adjust for better economy, efficiency, and power. Search open loop and closed loop feuling, I'm not going to type it all out but the basics are here. And your problem sounds like either a vac leak or a bad MAF or bad connection to the MAF.

[johnshop]

will be definitively reading that.

i will check for the most simple one for now maf.

and will follow this guide to check for my o2 sensors: http://www.twinturbo.net/nissan/300zx/F ... s/O2s.html

will report back.

[NolimitZ32]

BTW I'm originally from Houston and still have tons of contacts down there for Z32 related stuff, let me know if you need any specific parts and check out my "Nolimit's Moving to Australia Sale" Thread. All that isht is still either at my buddy's or at my parents house in Clear Lake.

[johnshop]

aww sweet, I am tired of getting parts online and taking a week to get here ahahah