Z won't start! Many symptoms leading up to it

Nissan 300ZX technical discussion forum: Maintenance, performance, installations, modifications, how-to's and troubleshooting.
HaveTwinZ
Posts: 3
Joined: Mon Oct 10, 2011 1:43 pm
Car: '92 300zx TT

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Hello everyone, first off thanks for viewing and having me at the Nico forums. Sorry to greet everyone with a technical issue but help is greatly needed.

So; every once in a blue moon my Z would idle rough and stumble upon acceleration in low RPMs. Around 3k it would clear up and run smoothly the rest of my drive. Just last week it started happening just about every other start up. Warm or not. it felt as if it were running on 4 or even 3 cylinders. Very rough and practically NO power! The car died on me at a red light. No sputter or stall just cut power and i didnt notice. I pushed it aside and got a ride to work later that night i went back to the Z and she started up and drove fine (no stumble) all the way home. Garaged her and Popped the hood later that night, fixed multiple vacuum lines that were BROKEN! and some weathered looking fuel lines as well just for good measure. Cleaned the air intake, reset the ECU and she ran like a beast from then on out. Idle was smooth and boost gauge works again. No stumble at any rpm or anything.

Now here's where it turned on me. I was driving some fun back roads the other night (boosting quite a bit too) when the engine started to stumble around 4k and boost was cutting in and out. Doing about 45mph and 7Lbs (stock gauge) it would boost and accelerate then cut boost and slow down. Felt very similar to topping out at max speed. This immediately Caught my attention, and driving up a Steep hill on heavy boost, the car lost boost altogether and ran N/a to the top of the hill. This makes me assume it's a boost leak. So I drove Under 3k to avoid any boost, to my work. I cooled the car for 5 mins or so before shutting it down. Hung out for 30 mins or so before heading home.

Here's the kicker. Car started and drove fine the whole way home (avoiding boost mostly) but right down the street from my house, at a stop, my car died altogeher like the week before. I checked all the vacuum lines and intake pipes. Couldn't find any thing.. The car cranks and turns over but won't start. Tried jumping her and to no avail.

Known problems:
ECU reads code 34 DET sensor
Blown seal on turbo or maybe oil line. Hasn't boosted like when I first got her (this happened long before hand)
Misfire in unknown cylinder. Ticking. (did coil pack test but nothing!)

I ran a multimeter through most components and everything checks out.

Hope this makes sense, as I'm typing this through my phone it's hard to review everything. But if anyone has any insight or ideas as to what I should try/test please help me out. I am a novice to this 300zx but I need to get her running. All and any help is greatly appreciated. Once again sorry for greeting you all on a bad note! But I need help and DON'T want to take her to a shop.

Thank you in advance! :sad:


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BigTDogg (MA)
Posts: 4194
Joined: Wed Aug 29, 2007 8:26 am
Car: 1990 Nissan 300ZX TT
Location: Boston MA

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How many miles on the engine and turbos?

7PSI indicates a code 34, as you found out. 9PSI is stock boost.

Did you check all the injectors for proper impedance?

Where are you located? Depending on location, I may be able to recommend a Z specialist in your area.

HaveTwinZ
Posts: 3
Joined: Mon Oct 10, 2011 1:43 pm
Car: '92 300zx TT

Post

Hey thanks for the reply. And sorry for such a delayed response, have been out of state so this issue wasn't too much of a concern lately. Anyway, I have 170k on the chassis and 100k or so on a swapped engine. (The previous owner swapped it before I had purchased it) But after some examination I found a hacked up ground wire between my ptu 'harness' (I have newer style ptu) and the temperature sensor that's left of the CAS (engine temp?) could a fried PTU be the cause of a sudden Engine fail and a non start? It sounds plausible to me.
The ground wire was severed down to the last two strands which eventually broke leaving the ground cable severed completely.

Also can I use a donor PTU from an N/A to test in my TT MODEL? or is the turbo model PTU different?

I'll be sure to post pics soon as well.

Oh and I'm located in the southern California. Closer to the San Diego area
Thanks for the help!

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BigTDogg (MA)
Posts: 4194
Joined: Wed Aug 29, 2007 8:26 am
Car: 1990 Nissan 300ZX TT
Location: Boston MA

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PTU is the same for all types of Zs

A fried PTU will cause a no start condition. Get the wiring straight before testing a new PTU though, or you could fry that one as well.

I know of a great mechanic in the Laguna Beach area, but you'd have to be able to get your car to him. PM me for his email address, he may be able to recommend someone closer to you as well.

HaveTwinZ
Posts: 3
Joined: Mon Oct 10, 2011 1:43 pm
Car: '92 300zx TT

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Turns out the PTU wasn't the issue. I did a very thorough soldering job on the severed ground wire, wrapped it tightly too. Plugged in the new PTU and still no start. One thing I did notice though was that when I turn the key on to accessories, before this issue, you would hear the hicas power up and what I believe is the fuel pump also. Now since it died I haven't been getting those sounds when I put the key into the acc. Position. All lights and everything else seems to be working ok, but the absence of those familiar sounds makes me think it's power related. Any additional help would be greatly appreciated.

BigTDogg - I believe my boss has a car trailer and he happens to live in Laguna as well, I'll ask him about bringing it next time he's down here. Could work out very easily for me :)


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