Irradical Idle and Odd Shifting. HELP

[BrianZ32]

Welp, im back here again

So i just came from my trip to San Diego, took DaiZy with me
And as i am arriving home from my two hour trip, i realized she was behaving oddly.
She has fluctuating idle and theres a bit of late shifting that is casing some jerking when it does. One observation i made was that there was white smoke from on top of the engine block
So may be oil coming from somewhere? I took it to a local mechanic and he basically told me that it could be in need of a major tune up. He stated he would have to take off the intake manifold and replace some hoses and whatnot. His hypothesis is that a valve seal might be bad. It is not the first time she has done this. Last time was about 8 months ago. At that time, we had replaced some vaccuum lines that fixed the issue. What do you guys think? Im trying to see if there is another alternative or something else that can be the issue so that way i dont have spend a pretty penny for a major tune up. Im sadly letting her go to a family friend. I am getting a Z33, (Younger sister) in about a month so im just trying to save some money.
1990 Nissan 300zx N/A
Only mods i have done are Popcharger and muffler delete. My mechanic believes these are the long term effects of the muffler delete. She has had delete for a year now. Please help a brother out here.

[rgregoryb]

Disregarding the white smoke, have you checked and set the TPS? Did the mechanic run the ECU codes?

[BrianZ32]

Disregarding the white smoke, have you checked and set the TPS? Did the mechanic run the ECU codes?

No, i can run the ECU codes myself, but he did not check the TPS
He is a private mechanic that did not have actual time to put his hands on it, this was simply from his previous experience working on it.

[rgregoryb]

A "major tune-up" sounds like a lawn mower mechanic's " response. I would want someone to isolate the specific problem.

[BrianZ32]

A "major tune-up" sounds like a lawn mower mechanic's " response. I would want someone to isolate the specific problem.

Thats why i got so frustrated, i want to find the issue and he couldnt help me at the moment.
UPDATE: its been two days since i returned from san diego, and the car ran rough the same day i returned. it ran normal yesterday and today so far...i have yet to experience high idle this morning...any ideas? I doubt this is an issue than can just go away on its own

[rgregoryb]

I would check the TPS, they can be erratic

[DCaff300ZX]

Do check the TPS, but I suspect your PTU harness and corrosion and possibly more corrosion in the normal places such as injector connectors, IACV, and CTS and sometimes even the CAS connector. A semi-short as occurs with oxidation corrosion causes a lapse in power and the jerky shifts most likely, and do look for a better mechanic as that one sounds like the type I avoid at all costs- I would have walked out without a word after that assessment.
There is an online service manual in the "everything you need to know about the Z32" sticky, do download it and it can be your best friend if you are mechanically inclined, and can still be helpful with pointing you in the right direction on certain problems such as you are experiencing with some tests and flow charts.
DO also hunt around as best possible for a Z32-specific mechanic as these cars do need more knowledge and experience than most normal mechanics have with them, and as you experienced with the shoddy "assessment", ask away here with any more specific questions, and Good Luck!

[BrianZ32]

Do check the TPS, but I suspect your PTU harness and corrosion and possibly more corrosion in the normal places such as injector connectors, IACV, and CTS and sometimes even the CAS connector. A semi-short as occurs with oxidation corrosion causes a lapse in power and the jerky shifts most likely, and do look for a better mechanic as that one sounds like the type I avoid at all costs- I would have walked out without a word after that assessment.
There is an online service manual in the "everything you need to know about the Z32" sticky, do download it and it can be your best friend if you are mechanically inclined, and can still be helpful with pointing you in the right direction on certain problems such as you are experiencing with some tests and flow charts.
DO also hunt around as best possible for a Z32-specific mechanic as these cars do need more knowledge and experience than most normal mechanics have with them, and as you experienced with the shoddy "assessment", ask away here with any more specific questions, and Good Luck!

UPDATE: I ran the ECU codes, 55
So no issues there
But i now noticed the idleing issue only happens every other day. And it only lasts a few mins and goes away. That is what was causing the odd shifting. With that being said, i dont have the proper knowledge nor tools to check the TPS. Is this something i can do myself? Figure only things ive done to my car is an oil change and installed coils myself. I also went to a speciality Z shop. Mechanic there told me i was over reacting. The white smoke could have been oil leaked through the valve seals and that i shouldn't have anything to worry about. Says that the odd idle is the computer trying to reconfigure itself. What do you guys think about that? What should i do in my case

[z.Leinbach]

All you need to check the tps is a 7mm small socket, and a volt meter. Well and a timing light.

Verify timing is at 15°btdc and then use the volt meter is reading .451volts at closed throttle. A very good vid is on YouTube.