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kenbam, Nissan Mechanic
Category: Nissan
Satisfied Customers: 390
Experience:  23 years in the trade, last 13 years training auto apprentcies
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Need assistance with a 91 300zx that idles roughly, sputters

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Need assistance with a '91 300zx that idles roughly, sputters and loses power when accelerating until engine warms.   Temp gauge died again after having ect sensor replaced 5 months ago. Ran conzult and has heated O2 sensor code. I think there may be something else wrong. Please advise...
I would be looking for air leak, Engine sounds like it may be running lean during warm up.

Temp gauge sender is different to the sender for the ECU. Its the one with the single wire.

Hope this helps.
Customer: replied 8 years ago.
Any guess as to where I should start looking for the leak? Is it running lean due to the heated O2 sensor or could it be something else also? How would I correct a lean condition?
O2 sensors generally make them run on the rich side, hows your fuel economy, any dramatic changes?

You can start looking for the leak by visually checking all your vacuum hoses, they are all getting on now if they are original hoses. Also, once the engine is warm and you have a steady idle, spray small amounts of wd40 or similar around the inet manifold area and listen for any changes in idle speed. The best method i have used, if its available to you is a leak testing machine. It pressurises the inlet manifold with an artificial smoke. Look for the smoke escaping and you have found your leak, although not everyone has access to the machine. The 300zx can be a pain to find an air leak.

Hope this helps.
Customer: replied 8 years ago.
Sounds like a plan, but what causes engine to sputter and lose power and almost stop when I press the accelerator when the car is not warm? Possible MAF sensor problem, rich condition, something else or just a vaccum leak?
Could be MAF, wouldnt hurt to clean it, you can buy spray cleaners for hotwire sensors. My money would be on the air leak though. Start by looking at the vacuum hoses, even start pinching them off listening for a change in engine note.

Let me know how you get on.

kenbam and 4 other Nissan Specialists are ready to help you
Customer: replied 8 years ago.
No problem