Hi, bit of a long story bit ill try keep it short.

2 years ago I bought my 300 TT. It was in pretty rough shape. I took it to my garage and tried starting it for the first time (parked for 10 years previous). After ripping out the old Clifford alarm and adding new fuel, plugs, oil and battery it fired right up, smooth as butter! Drove nice and boosted no problem. I then went and started the restoration. 

Car was stripped down to 90% bare shell to fix rust on the floor, roof, sills, and a bit in the engine bay. Full inside out respray was done, and sealed underneath. Engine removed and reinstalled when painting was finished. I put the car back together and was very happy with the outcome, until....

The idle was never right from when I put engine back in. I done water pump, timing belt, all auxiliary belts, cleaned inlet manifold, throttle bodies, IACV ect. 

The car is running extremely rich and you have to keep on the throttle to keep it running, there's a small mis at 1000rpm,

1) all the plugs are sparking,

2)I smoke tested for vacume leaks,

3)no codes when I flash the ECU,

4)TPS seems fine

5) IACV is working 

6) PTU was replaced

7) brand new MAF

I'm exhausted trying to get it sorted as the plan was to have a nice summer driver, especially after the time and ALOT of money I'm into it. I'd appreciate if anyone has any ideas. Thanks!

Couple of suggestions just based on my own experience, not much of a mechanic 😉

Mine sounded like a misfire or rather an intermitttent stumble on idle or low revs. Turned out to be a broken/leaking injector or collar. Early ones are permanent live, so a crack could cause a short. 
 

Have you tested/reconnected the o2 sensors in the exhaust? Although that may show up in ecu?

 

also, 10 years stored, worth swapping the cam belt to avoid age related failure

How about the engine harness the plastic connectors crack and get corrosion especially the injectors, look for green corrosion.

1 hour ago, Bones28 said:

How about the engine harness the plastic connectors crack and get corrosion especially the injectors, look for green corrosion.

Injectors are my next port of call, the ones I've been dredding 😫 are they a pain to get to like everything else on the car?

49 minutes ago, OdhZ³² said:

Injectors are my next port of call, the ones I've been dredding 😫 are they a pain to get to like everything else on the car?

Unfortunately yes a bit of a pain, you need a small screwdriver to unclip the sides of the metal clips and ping them off, have a magnetic ready to catch them.

I would recommend making sure your fuel pressure is 3 bar as it should be, takes 2 mins. buy an 8mm fuel line adapter with gauge for 20 quid from eBay, then add that into the fuel line just after the filter.

If OK then remove plenum. Pull the fuel rail out but leave the injectors in place, hook the rail back up to the fuel lines and put the connectors on without the clips, then place some blue roll down somewhere in the engine bay and remove the CAS and turn it by hand, this way you can see the pattern left by each injector, you want all 6 marks to look the same. It will be immediately obvious which injector is causing the issue. If you had an injector stuck open, be sure to change the oil once the injector is fixed

The injector plugs often have green corrosion whilst they are unplugged it may be worth cleaning them with a set of diamond tipped tweezers, you can get a set from eBay for £15 . laser tools part no 6546

Edited March 23, 20241 yr by Toomanyzeds

9 hours ago, Toomanyzeds said:

I would recommend making sure your fuel pressure is 3 bar as it should be, takes 2 mins. buy an 8mm fuel line adapter with gauge for 20 quid from eBay, then add that into the fuel line just after the filter.

If OK then remove plenum. Pull the fuel rail out but leave the injectors in place, hook the rail back up to the fuel lines and put the connectors on without the clips, then place some blue roll down somewhere in the engine bay and remove the CAS and turn it by hand, this way you can see the pattern left by each injector, you want all 6 marks to look the same. It will be immediately obvious which injector is causing the issue. If you had an injector stuck open, be sure to change the oil once the injector is fixed

The injector plugs often have green corrosion whilst they are unplugged it may be worth cleaning them with a set of diamond tipped tweezers, you can get a set from eBay for £15 . laser tools part no 6546

Thanks for that, I'll be sure to look into it

On 23/03/2024 at 08:23, OdhZ³² said:

The car is running extremely rich and you have to keep on the throttle to keep it running, there's a small mis at 1000rpm,

Running extremely rich is also a symptom of failed damper (FD). It's worth replacing the FPR and FD as a matter of course as they

can fail with age. Details in link.

http://www.twinturbo.net/nissan/300zx/forums/general/view/2610744/Here-is-how-it-works.html

Small Update:

I removed and cleaned the IACV thoroughly and it's running under its own power now, we'll atleast I don't have to constantly have throttle to keep it running. 

I removed the pipes into the throttle boddies and there was a lot of carbon built up (see photo of rag). It's running alot better after this.

I removed the injector connectors (what a pain 😢) and surprise surprise they wer corroded (see pic). I cleaned them with a file and contact cleaner but didn't see much of a difference. The idle is fluctuating from 600rpm to 1500rpm intermittently. I done the "ear" test with a metal bar on all 6 injectors and they seem to be firing like they should. 

I didn't check the fuel dampner ect yet. 

Any input extremely welcome 🙏 

Dielectric silicone grease will help to prevent the ingress of moisture and oxidation/corrosion of the injector connectors.

15 hours ago, OdhZ³² said:

Small Update:

I removed and cleaned the IACV thoroughly and it's running under its own power now, we'll atleast I don't have to constantly have throttle to keep it running. 

I removed the pipes into the throttle boddies and there was a lot of carbon built up (see photo of rag). It's running alot better after this.

I removed the injector connectors (what a pain 😢) and surprise surprise they wer corroded (see pic). I cleaned them with a file and contact cleaner but didn't see much of a difference. The idle is fluctuating from 600rpm to 1500rpm intermittently. I done the "ear" test with a metal bar on all 6 injectors and they seem to be firing like they should. 

I didn't check the fuel dampner ect yet. 

Any input extremely welcome 🙏 

Oh pretty bad I replaced mine with new pigtails, you will need to check all the connectors, tps everything.

I have a new TPS on route, I'll have it Friday. I think this is the issue

24 minutes ago, OdhZ³² said:

I have a new TPS on route, I'll have it Friday. I think this is the issue

Make sure the connector is not corroded.

I would say to try and diagnose what is actually at fault before ordering parts willy nilly, Nissan data scan & a cable is relatively in-expensive compared to the price of quality replacement Z parts

You said you have a brand new MAF - you must have shelled out a lot of money for a new OEM MAF? The aftermarket pattern ones never work right so if you've put one of those on your better swapping to a used genuine Nissan unit.

On 23/03/2024 at 22:25, Toomanyzeds said:

.........The injector plugs often have green corrosion whilst they are unplugged it may be worth cleaning them with a set of diamond tipped tweezers, you can get a set from eBay for £15 . laser tools part no 6546

Great tip mate, thanks - I have just ordered a set of these, definitely handy to have around the garage 🙂