PTU subharness delete

[demonZ73]

i need help with removing the subharness on the 1990 nissan 300zx im looking for a write up or a detail discription on cutting and reactching the wires please help.....thanks

[t.mcginley.jr]

You mean how to wire in the PTU directly to get rid of the 2 extra connections?

AKA from this:

----[] [] ----- []PTU[] ----- [] [] ------

To this:

------ []PTU[] -------

where [] = connector
and ---- = wire harness

[itsa300zx]

Here you go, free fish.

http://www.aus300zx.com/forum/showthrea ... hlight=ptu

[demonZ73]

thanks for the help .....itsa300zx i dont really understand the the photo and the reading well i do its just that it doesant look like thats what im trying to do ....on my 300 i beleive i have the newer style ptu (because it does NOT have the aluminum fins) now i have what looks like an unnessecary harness that i was told that can corode and cause problem which is posibble what is happeneing right now .....mcginley ur little sketch makes a little more sence just tring to get ride of those extra wires and plug the ptu into the main harness ..

[itsa300zx]

In that photo, top is the new style with grey connectors from the sub harness and bottom is older with connectors from the EFI harness. Cut sub harness connectors and connectors at the EFI harness, use the purple lines as solder joints. (ie, on the left side, solder the brown wire with the white line(from grey connector) to the bottom black wire of the EFI harness (from black connector). Maybe post a picture of what you got.

[demonZ73]

thank u that makes alot more sence

[t.mcginley.jr]

So you got it figured out? It's not too difficult once you have a visual of it

[demonZ73]

ya it was actually alot easier than i thought it was going to be however still running like sh*t it will not idle............and when i tap the throttle kinda of rapidly it will not even rev ......it will only rev when i slowly press the throttle, one guy recomemded my PTU itself which i have not replace.............anyother ideas anyone????

[itsa300zx]

Have you adjusted or checked your TPS?

[demonZ73]

ya it has a brand new one and i adjusted it to .4 volts

[t.mcginley.jr]

Is the PTU a newer style? Have you checked your injectors and CAS? How old are your PCV valves?

[demonZ73]

yes i beleive it is a newer style ptu cuz it does not have the aliminum fins, i have brand new injectors and pcv valves, and as far as the CAS i assume its good cuz from what i hear the car will not run at all if its bad, and when i turn it the timimg mark does move

[t.mcginley.jr]

Ok so it's not your injectors, pcv valves, CAS, TPS, and probably not your PTU. That leaves... MAF, IAA valve, vacuum leak, the throttle cable itself, dirty/binding throttle bodies, etc.

You can try doing this and see if it helps: http://s95014253.onlinehome.us/63104/15 ... on*id*val*

Also pull the plastic intake pipes and make sure your throttle bodies are opening correctly when the pedal is depressed, and make sure the cable itself is tight and adjusted correctly.

A vacuum leak, even a small one, can cause rough idle and lack of power.

[demonZ73]

i have a second hand MAF i just put on but 100% know it was good beacause it was tested at ashspecz on a car before it was mailed to me so i know its not that, IAA has been comptly remove dissasebled, cleaned, checked, set and put back togther so i know its not that, same exact thing with the throttle bodys,.......althou the vaccuum leak thing has me thinking especially when u say even a small one, because i did alot of delete type stuff and i think i have a small hole not plugged somewhere i know there is one on the balance tube thats open, however i cant imagine this small a hole is causeing this much trouble.........anymore help is great....thank u

[t.mcginley.jr]

So what did you delete? EGR, AIV, TB coolant lines?

[demonZ73]

Yes exactly that .... All 3 and removed the unessesary solenoinds however the problem was happening before I did all that

[t.mcginley.jr]

Are you sure you didn't leave any open vacuum lines or uncapped ports?

[demonZ73]

what and where are the important vaccum lines that i should check........i do know of the ones coming from the pcv valve those i know are good, however where els can i have a vaccuum leak

[demonZ73]

anyone?........please

[t.mcginley.jr]

Alright go over your symptoms one more time if you can, all of them. I know you have eliminated a number of things already that aren't causing the issue but I just want to make sure I know what the problem is exactly.

[demonZ73]

sure not a problem ill start from the beggining..........i have rebuilt the entire motor from top to bottom:
1. all new gaskets and seals
2. rebored cylinders .020 over w/ oversized pistons
3 shaved heads
4. stage 3 500 cams jmf from import parts pro
5. full stainlees exhuast
6. new pcv valves
7. new and adjusted TPS
8. new MAF
9. new fuel injectors (cleaned fuel rail)
10. new injector connecters
11. new fuel temp. sensor and coolant temp sensor and connecters
12. throttle bodys removed cleaned and even syncronized back together (new gaskets)
13. idle air adjustment assemmbly removed cleaned inspected and put back together (new gaskets)
14. water coolant delete, IAV delete, EGR delete.
15. currently not throwing any codes.
16 have done a power balance test all coils seem to work and get spark.
17. fuel pressure good.
18. compression test good.
19. PTU sub harness delete
20. timing is correct and (and yes i did count the cogs correctly)
21. CAS seems to be good because car does run
22. good battery
23. new ngk stock spark plugs

now the symptoms are the car will always start, however will not idle and has very bad throttle response, like......will not rev when i press the throttle rapidly, althou will rev when i press it slowly, also the idle air adjustment screw has no affect on the speed or idle of the engine what so ever even when i turn it while running with the iaa plugged in or not. now even after replaceing all those external parts of the motor the symptoms have never changed not even a liitle, in other words after replacing a part or doing a delete i tried the car and no differance...........it aslways still ran like crap. well now that i think about it i will say this i pulled all coils and they all did get spark. but when i left all them in and then pulled the connecter to the #1 coil it did idle down wich is a good sign that the coil is working, however when i did the other coils from what i remember i do not think they idled down like they were suposed to (this of course was being done with me holding the throttle open to keep it idling)

things i have not replaced or checked ......02 sensors, PTU
this is everything i can remember i hope this helps if u have any questions let me know or if u can help me it would be great iv been working on the car for 4 years and would just like to get it to run right........thank you anyone

[t.mcginley.jr]

Ok I think at this point you should try putting in a new PTU, or at least a known good one. The O2 sensors shouldn't cause this kind of problem, usually they only make the car run rich when they're messed up. Someone had slightly similar problems that you have in a different thread and solved it by throwing in a new PTU:

running-out-of-ideas-t564182.html

[demonZ73]

cool thanks ill give that a try and let you know