Rough Idling and Occasional Stalling

[Paul]

Hello EricTheCarGuy-nians,

😆

Car Details:

Car Year/Type/Made : 1987 Nissan Sentra B12
Engine : E13 or E16
Transmission : 5 spd manual
Km : 244,000 km

Few weeks ago my B12 was running smoothly though I have a feeling there was a slight drop in fuel economy, one day when I was driving it to my office I step hard on the gas and next is the power surge, when I was starting to slow down from 80km to 10km, my car stalled (engine turned-off), since I was still in a rolling motion I was able to bring it back on but the idling became noticeably rough when I was on full stop. After that event, I started experiencing rough idling during start-up and running.

I experience rough idling during:

• Full Stop
• Cold Start
• Coming of from High Gear Motion to Rolling Resistance motion
• Slow rolling

I experience engine hesitation/stalling during:

1. Stop and Go
2. Full Stop

I diagnosed the car yesterday, and thought it was the Electrical Distribution, so I replace the spark plugs (there is also noticeably rich amount of carbon on the tips for #s 2, 3, 4, aside from the carbon there is also oil in it as well as outside the plug’s well),

I also replace the distributor cap with a new one as I have noticed some corrosion on the four pins inside (there is already a carving)

I also replaced the air cleaner with OEM air cleaner

Unfortunately, none of the above fixed the problem, albeit I noticed the following:

1. When Temperature is moderate (Engine is already on operating temperature) the idling does not drop or it appears the car is running smooth but I’m nervous about it going to stall
2. During Start-Up, car is one-click start but then eventually if you race the gas pedal its starts go on rough idling.
3. Sometimes it starts and perform fairly well but there are some interval the idling starts to fall, sometimes I would be able to bring it back to steady by revving up the engine but sometimes it wont and just would stall.

I think its hard to diagnose the car when its already on its operating temperature, I’ve also read that its possible that there’s a vacuum leak, I tried some water but I’m not sure if I did it right on my first try.

I suspect some vacuum leaks but how am I sure it is? How can I accurately check for it?

I rode to the office today using the car, it run good but I notice some performance drop though it still reach 100kph.

Update:

I tried to do some vacuum leak by smoke, I did by unplugging one vacuum hose and putting the smoke to it, at first there was no smoke, but when I removed the air cleaner, a thick smoke just went out, is it normal that that smoke comes out of the carburetor? I’ve also noticed that the gasoline deposited in the bank of the carburetor disappears a day or two after being unused.

Can somebody help me diagnosed and fix my car? What else do I need to check?

Topic

[college man]

If I remember right there is a fuel filter on the drivers fire wall.
You may want to change it.

[Paul]

Hi college man,

If I replaced the filter, what should be my expectations?

Should the fuel be retain in the bottle?

Also, would this fix the idling issues I’ve mentioned above?

Lastly, when the car is running, is it expected to have the fuel filter bottle to be full? I’ve noticed that mine was only fill up to 3/4, any signs of fuel pump going out?

[college man]

[quote=”mirageservo” post=122844]Hi college man,

If I replaced the filter, what should be my expectations?

Should the fuel be retain in the bottle?

Also, would this fix the idling issues I’ve mentioned above?

I just re read your post. If oil is on the plugs and inside the well
This is part of the problem. Ignition components won’t run in oil.
When you start the car cold does the car idle up or if your car has
ac and you turn it on and the ac works does it idle up? It sounds like two
issues here. oil in the plug well means the seals are leaking. Also your
carb/IAC sounds like it needs to be cleaned. 3/4 full through the filter is
normal for a carb.

[Paul]

Hi college man,

When I start the car, these are the possible scenarios:

• If gas has already evap from the carb, the car will start but will easily die down
• If gas has already evap from the carb and the filter bottle has gas in it, the car will start and eventually die down, need to restart and try again, might lead to rough idling or sometimes will die down again.
• If gas is on the carb and the filter bottle is dry, the car will start and if gas is enough will idle rough and eventually die down, on next start car will be on rough idling until you race on the gas pedal, car will be on smooth idling.
• If gas is on the carb and the filter bottle is filled with gas, the car will start and will idle

I do the following before starting:

1. I race the gas pedal once,
2. I step on the clutch cable (I recently found out that it helps to lessen the weight of the engine during crank which helped in the starting of the car, albeit I am not aware if this is bad to any components – car does not have a clutch ignition switch control fyi)

After the car have start, I do the following:

1. I slightly step on the gas pedal until the car idling stabilizes.

IAc – AirCon?

Also, what leak, valve or pistons?

Thanks,

[Author]

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