# Please help, rough / high idle



## jennab (Nov 7, 2014)

Hi,

Im helping a girlfriend with her new 89 sentra. I've done hours of research but still have questions.

The car has a very fast idle, maybe 1500-2000 rpm or faster. It will also die coming to a stop occasionally.

I researched here and inspected the vacum hoses which look pretty good. No splits or visible holes. Ran propane all over and didn't find any leaks that way either.

I cleaned all the electrical connections around the throttle body. The air flow meter had the most corrosion. Some plugs are missing their wire clips. I also sprayed the wax type fast idle cam with carb cleaner and some silicone lube.
The idle seems to have stabilized slightly after this but it's stiil high and surging up and down.

The ECU gives code 25 which might be the AAC or FICD or a third solenoid I cant recall, according to posts here.

I tried to remove the AAC valve from the TB to clean it but it's held on with screws and I couldn't get them loose with the TB in place. How do I remove the AAC to clean it?

I did pull the FICD solenoid out and it looked spotless as did the passage behind it.

I also read to clean the AIV. How is this done, just remove it and take it all apart?

Id like to check timing but do not have a FSM. The sticker says 7degrees I think but at what RPM? Also what vacum hoses to I need to plug to check properly and how can I get the idle down to say 800RPM to check the timing.


I downloaded the Pulsar manual which is some help but still cant figure it out. Any suggestions? Thanks


----------



## rogoman (Dec 16, 2004)

The fast idle may be caused by a bad IACV - Air Regulator. The air regulator provides a high idle when the engine is cold. Also check out the IAA unit which consists of the AAC solenoid valve, the FICD solenoid valve and the idle adjusting screw. The IAA unit can be removed and cleaned out.


----------



## jennab (Nov 7, 2014)

Thanks so much rogoman,

I don't have a sentra FSM but have the stanza one. Which is the IACV - air regulator? Is it the air flow meter in this picture?










I didn't mention but I have a GA16i. Does that have an idle adjusting screw?

We also lost the spring for the AAC. Can anyone suggest a replacement? would a ball point pen type spring have enough force?

Thanks again.


----------



## rogoman (Dec 16, 2004)

If your engine uses a single throttle body with one fuel injector, then it looks like there is no Air-Regulator. It uses a wax type fast idle cam as shown in your picture. I'm not familiar with this setup; maybe someone else can chime in.


----------



## smj999smj (Jan 1, 2006)

Not much to a wax element. Coolant jacket runs behind it. As it warms, the wax is heated, moving the plunger to take it off fast idle. Reverse happens when it gets cold, again. Sometimes the coolant line will get clogged, restricting the flow past the wax element, and keep the idle up. Sometimes the wax element gets seized or leaks coolant, but they are pretty reliable, overall.


----------



## 89B12 (Sep 1, 2013)

Would the wax element make the engine rev higher and higher as it warms up? It seems to be a simple mechanism, so I don't see how it could, but -- my car starts and *begins* it's normal cold, fast idle. As the minutes pass, with no interaction with the accelerator, the engine gradually gains speed. It isn't an up or down rev -- it is consistent, although it just keeps climbing. The most I've let it run is 8-10 minutes. If the accelerator is pushed, it will almost "bog" for a second, like it has a vacuum leak, then rev, only to return the high idle is was at and keep climbing.

I have pinched off each vacuum line I can get my fingers on, although I have yet to pinch off the brake booster hose. The car also emits a hazy smoke. It doesn't smell look or smell like oil smoke. It has a hot, warm smell to it -- almost like it's lean? Not sure . . I've never seen one do this.

The car ran perfectly, with no smoke, and was my daily driver until October. It then sat for about a month and a half, only to be started and driven onto a trailer and started to be driven off. At that time, it still ran fine. After sitting another month or so, I changed the thermostat and had a really hard time getting the car started -- the accelerator had to be pressed, and I had to keep "milking" it to keep it running, only to discover the aforementioned issue. One last clue is my water temp gauge is no longer active. Might I have disturbed a ground or some other connection during my thermostat change? I don't see how, as careful as I was, but it is a variable.

I haven't checked for codes, but I guess that would be the first recommendation?


----------

