Car hesitating around 2000 RPM's

Not familiar with Stanzas, but I've known it on other Nissans if either the ignition is too advanced or the wrong brand (non-NGK) plugs are used or if the engine is a little hotter than normal (doesn't always show up on Nissan temperature gauges as some have a dead spot in the middle). If it's worse after a hard run then one of these is likely, if not perhaps it's emission control stuff gunged up.

Have you checked the catalytic converter for blockage? I had the same problem with an '85 Pulsar. Catalytic converters do clog up, especially if the car is burning a little oil, and once it starts, it will only get worse if the car is driven regularly. If not replaced, a clogged cat could result in burned valves, rings, and other engine components from the ever increasing back pressure.

try removing the vacuum hose on the EGR valve.

Get back to me with your findings

Funny that you mentioned it, I had a 90 Stanza once, and the only time it ran good is with the EGR hose unplugged. Had way more power.

the EGR system on most nissan require cleaning very so often. But Most of the time even dealer service neglect it!

I have come across few sentra/pulsar/se-r forum that has details on how to clean them. do a search on google or something!

good luck!

AV wrote:

First of all, good job on following instructions and your description of your problem and the steps you have taken to remedy the problem.

ok, here is the cause of your problem, by un hooking the vacuum lint to the EGR valve you have basically stopped the introduction of EGR gases into the combustion chambers, the reason EGR is used is to lower cylinder temp and reduce NOX (oxides of nitrogen) emissions which is a harmful gas into the atmosphere.

the way EGR gas is introduced into the engine is via 4 ports which are located on the intake manifold, the reason the engine surges is because too much EGR gas is getting into one of the cylinders, the reason that is happening is because the EGR gas is not getting evenly distributed, the reason for that is because 1 or more out of the 4 EGR ports are clogged up with carbon.

if too much EGR gas is introduced into a cylinder it displaces the correct fuel to air mixture ratio causing what's called a lean cylinder missfire, that is what you are feeling when you are driving.

the fix. The fix is to remove the upper part of the plenum to access the EGR ports and clean them out, it is not the kind of thing I can describe how to do within an e-mail, If you take it to a shop that has some experience with Nissan and ask them to do it they might know what you mean, the dealership should also be able to do it too.

Thank you for a great explanation of what it does. It appears that my 96 Quest is affected by this problem. Does it also have ports which have to be cleaned or is cleaning the valve sufficient?

the V6 engines have a different way on injecting EGR gas into the engine, my guess it that you air flow meter/hot wire modulator has become dirty and needs to be cleaned