# 99 nissan altima surges.



## tmoneymike (Jun 20, 2012)

having problems with my 99 altima. It surges through the driving range mostly while under light acceleration and cruising. The engine would loose some power for a split second then go back to normal. No surge while heavy acceleration tho. Ive changed the plugs and wires and also the fuel filter thinking that was the problem. but no luck. soo hopefully i can get some helpfull info on how to fix this problem. thank you


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## smj999smj (Jan 1, 2006)

"Surging" usually occurs when an engine is lean. A common area on these engines is the intake gasket, but any vacuum leak, low fuel pressure or volume, faulty or dirty MAS or a faulty front O2 sensor can all make an engine run lean, as well.


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## tmoneymike (Jun 20, 2012)

A faulty o2 sensor would throw a check engine light right? whats the best way for testing to see if there is vaccume leak? and also how can u check to see if the mas is faulty?


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## smj999smj (Jan 1, 2006)

Spray carb cleaner around the intake gasket, or an area you suspect may have a leak, while running; if there's a leak, you'll notice a change in RPM while you're spraying the area. A faulty O2 sensor will often, but not always, set a code. If it has become limited in it's range but still cycling enough to not set a code, it won't. The best way to check a MAS is with a scantool that views ECM datastream and compare it to the specifications in the FSM.


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## midlife (Sep 26, 2012)

smj999smj said:


> Spray carb cleaner around the intake gasket, or an area you suspect may have a leak, while running; if there's a leak, you'll notice a change in RPM while you're spraying the area. A faulty O2 sensor will often, but not always, set a code. If it has become limited in it's range but still cycling enough to not set a code, it won't. The best way to check a MAS is with a scantool that views ECM datastream and compare it to the specifications in the FSM.



Yeah, I have heard of this test, but also heard that you have to spray a very little amout of it and when the car is not warmed up.


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## smj999smj (Jan 1, 2006)

You can do it when the car is warmed up, but it's best when it's cold as the parts expand as they heat up. If the intake manifold is really bad, it won't matter whether it's cold or hot.


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