# 1994 HB HD VG30E Manual trans 140k mi IDLE PROBLEM



## Driftme (Nov 25, 2007)

Hi everyone, new to the forum.

I have an idle problem on my HB. When I first start up when it's cold outside the idle is real low for a few seconds then rev's up and idle's high for a few minutes (HD model, no tach so not sure what the rpm's are) and it runs really rich as you can smell the gas. After it warms up, when you come to a stop it idles fine for about 10 secs then it starts a miss and have a small sputter. Other then that it drives perfect, No CEL. Not sure where to start. Any idea's?


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## smj999smj (Jan 1, 2006)

Could be any of a number of reasons...so, you need to start with the basics...usually a good tune-up. Now that doesn't mean go out and start replacing parts! Inspect them and replace as needed. Generally, if you follow the manufacturer's recommended service intervals, the tune-up parts should be in good shape. Remember to stick with genuine Nissan or NGK ignition parts, such as plugs, cap & rotor, wires...I also prefer to stick with genuine Nissan filters, when possible. Plugs and filters are usually replaced at 30000 mile intervals (platinum plugs can go double that or more). I usually recommend a new cap & rotor every 60000 miles and ignition wires at 100,000 miles. I also clean the throttle body out every 30000 miles, as well. Timing belt should be replaced at 105,000 miles. Check for any vacuum leaks, especially the vacuum hose to the fuel pressure regulator at the back of the engine. Wiggle the MAS harness connector while running and see if the RPM jumps; it was a more common issue on 95 models, but there were occassional issues of a bad ground connection to the MAS. If this is the gas, the pin in the connector should be replaced along with adding a supplemental ground wire to the one of the two EGI harness ground points on the intake plenum (not far from #3 spark plug). You would have to get the pin through a Nissan dealer as it's included in their harness repair kit from Kent-Moore. Also, make sure those EGI ground connections are clean and tight! Also, make sure the coolant is reaching proper operating temperature and the engine coolant temp sensor is operating in proper range. If the ECM senses the coolant is cold, it will keep the engine running rich. 

Adjust the timing and the base idle. Vehicle should be fully warmed up prior to adjusting the timing. The procedure for adjusting the idle is a bit lenghty if you follow the manufacturer's procedure. Base idle adjustment is critical, however, for proper operation of the AAC valve, which maintains the idle speed under loads and controls your fast idle speed for cold starts as commanded by the ECM. If you want the full procedure, e-mail me at [email protected] and I'll see if I can download it and get it out to you. The quick method: Adjust the idle speed screw on the AAC valve to 750 (+/- 50) RPM. Disconnect the AAC valve harness connector and adjust idle to 700 (+/- 50) RPM and reconnect AAC valve harness connector. 

These engines were occassionally prone to misfire, especially when cold or under a load, due to dirty fuel injectors. A bulletin was released concerning this matter. A professional fuel injection cleaning service often cured this problem, but you could get a faulty injector now and then. 

This should give you a good starting point.


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