1990 Z32 starts but no idle/limp mode help

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Erasaqd
Posts: 2
Joined: Mon Mar 07, 2022 1:23 pm
Car: 1990 Nissan 300ZX NA 5-spd

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Short version: My 1990 z32 won’t start. Code 34, starts but doesn’t hold idle and limp mode. Idle drops after few seconds of being on. It has knock sensor bypass, CAS is centered and plugged in. PTU is updated from previous owner. Has good compression. Has fresh fuel. No corrosion on coolant temp sensor or PTU. Can Drive but barely. Motor was inspected and is healthy. Help pls :wtf2:

Long version: I have a 1990 z32 that I bought with bent valves on cylinder 4 from a bolt laying in there. Had 0 compression on cylinder 4.

I replaced the head and put the car back together timed correctly, of course everything was torqued to spec and put back together as the FSM instructed. Deleted the nightmare of an EGR and those coolant lines plus welded them shut. Here’s the problem.

Car still doesn’t hold idle just like before. When I go to drive it it goes right into limp mode and sounds like trash, misfiring. Compression test is solid across the board. Fuel filter is good, spark plugs look brand new. I suspect the coil packs however I’ve been told it’s rare for them to go bad.

Code 34 is present.
I cleaned the connectors to the CAS and hit it with electrical cleaner. I did the same for the coolant temp sensor, water temp sensor is not present next to coolant sensor instead there is a ground no idea why.

As for the PTU. I called Nissan and they said it’s likely the previous owner did the recall for the PTU as they have no pending recall on my vehicle. PTU is a black box and looks great and has no green corrosion. Cleaned it anyways. Still not working.

Looks like the previous owner ripped the knock sensor wire from the plug. I thought nothing of it when assembling it as I was going to bypass it anyways with a 1m ohm resistor. Did that, still not working.

The fuel injectors plugs were cut and new ones installed via previous owner. Perhaps the new style injector upgrade. Regardless, the harness was messed with and I suspect I’ll be needing to buy another harness. Problem is, that new harness will cost around $600. To avoid that, I’m hoping someone will answer my prayers in this thread. What the heck is wrong with this car. Im buying new coil packs and spark plugs and injectors. If that doesn’t fix it, I’ll truly be at a loss of words.


Erasaqd
Posts: 2
Joined: Mon Mar 07, 2022 1:23 pm
Car: 1990 Nissan 300ZX NA 5-spd

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Update: Now I’m getting code 55. PTU wasn’t making contact, had to force it some ways in to get the car to fire again as it decided to not start this morning. I changed spark plugs which made it run a whole lot better; however cylinder 1,4,6 have no fuel so car still dies out, need to change those injectors and/or test them to see if it’s the harness. Fuel pump also might be on its way out. Gonna change that and update y’all to see if it runs.

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NolimitZ32
Posts: 7112
Joined: Fri Jun 27, 2008 9:07 am
Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
Location: Houston, TX

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Ah the fascinating world of Z32 ownership. I feel for you bud, let us know what else you come across.


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