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Q: nissa d21 z24 carburated strange rattling noise

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I am the owner of a 1987 Nissan 4x4 d21 z24 carbureted. First of all, the engine has been completely rebuild, new pistons and everything related to that , new head and gasket , new valves , and new timingchain/kit. , etc etc..... I swapped out the old carburetor with a much better , (rebuild one). The problem from the beginning was that the engine could not stay idle, at least not at 8-900 rpm as it should. at 1000 rpm and above idles fine. And from the begining i had this rattling noise from the engine , not at startup , but when i release the gaspedal after acceleration and kept the gaspedal in the midrange (cruising). no specific rpm. When i accelerate and braking with engine no rattling noise , only with gaspedal in midrange, (sounds like a dieselengine).

My car has 107000 miles.
My car has a manual transmission.

A: Hello. In regards to your idle speed issue,...

Hello. In regards to your idle speed issue, I would recommend tuning and adjusting the carburetor until the correct idle speed is achieved.

As far as the rattling noise goes, firstly I would check to make sure that the engine has adequate oil, and that it is clean, as the tensioner, as well as the valve lifters on that engine, use oil pressure to work. If they are starved for oil, for any reason at all, it can compromise their ability to do their job.

The rattling noises you are experiencing may be either a result of a loose chain, perhaps due to an improperly functioning chain tensioner, or perhaps lifters. If your vehicle is turbo, I would also double check to make sure that you have no vacuum leaks, and that your turbo diverter or recirculation valve are functioning properly.

If you need assistance with this, feel free to contact a certified mechanic who can pinpoint the rattling noise in your engine and make the appropriate repairs to get your engine running normally once again. Good luck.

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