Rough Idle & Some Questions

All things Altima Coupe.
Xenoseal
Posts: 37
Joined: Mon Feb 11, 2008 2:44 pm
Car: Altima Coupe 3.5SE

Post

Hi All,

Car: 2008 Altima 3.5 CVT, about 115k miles. Sole owner of the vehicle. Spark plugs replaced recently at the dealer. I'm not really a "car guy" but I've been able to handle most repairs myself.

I've got a rough idle while stopped or in neutral where RPMs drop below 700, the engine will shudder for a few moments and then come back up to normal. Rinse and repeat every 20-30 seconds or so. I'm going to go through my list here this weekend, but I have a few questions.

- Check / Clean MAF & Intake.
- Check / Clean Throttle Body & Sensors (Next to the intake? That area)
- Check / Replace Vacuum Tubes.
- Check / Clean the Butterfly Valve on the left side if facing the engine. (Opposite the intake? I don't know what that's called.)
- Seafoam
- Throttle position reset procedure

1) Does anyone know the ID of the little vacuum tubes? Looks like 3.5 or 4mm. I'm going to order silicone replacements.
2) I hear a sound coming from the butterfly valve / left side when facing the engine. The best way I can describe it is the "hiss" or "whine" you hear when you turn a water faucet on partially.
(EDIT) -- The hiss does not stop immediately when the engine is cut off. Goes for a second or two more.
3) Any other suggestions for this?


Thanks


Xenoseal
Posts: 37
Joined: Mon Feb 11, 2008 2:44 pm
Car: Altima Coupe 3.5SE

Post

Just checking back after the repairs and cleaning this morning.

I did everything except the Seafoam. (That's tomorrow morning.) The idle problem appears to be fixed, but also lead me on to another possible repair.

1) I removed the RH Power Valve (what I had called the butterfly valve on the left side, where I am hearing the hiss sound). Removed the 4 screws using T25 and it pulled off without much issue.
2) Inspected and Cleaned. The gasket looked good, but there was a lot of oil on the valve and in the intake manifold collector. I cleaned up the oil as best I could. (Bad PCV valve?)
3) I replaced all the small vacuum hoses I could find at the top of the engine. The OEM hose was 7/64 (2.8mm), I replaced with 3 mm thick walled silicone. Most of the connectors measure >3.5mm.
4) Pulled off my Intake and cleaned the Throttle Body & MAF. Throttle body wasn't bad, but had some buildup.
5) Re-assembled the Intake.
6) Performed the Accelerator Pedal Release & Thrtottle Valve Closed Position reset.

When I turned the car on, idle was about 1500 RPMs / quite a bit high. Probably due to aftermarket Intake.

7) I drove for a bit to bring the engine to temperature before repeating # 6) and performing the Idle Air Volume Learning.

Idle stayed high and CEL stayed on.

8) Performed a ECU Reset Procedure and Repeated Steps 6 & 7.

Everything is working good now. Idle is a steady 700 RPMs.

I still hear the "hiss" from the the area around the RH Power Valve area, this may be normal operating sounds and I'm not familiar or it might be something else, I will continue to investigate that.

I did find quite a bit of oil up in my Intake Manifold Collector while looking at the RH Power Valve, searches seem to indicate that this would be a bad PCV Valve, which could have also sparked the idle problem. I am going to pick up a replacement and do that sometime this week. I'll pull the valve off again in a month or so after that and check it again. I snapped a picture before cleaning it up, see below.

https://imgur.com/7GLuKFN

Image


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