I've tried it all: Idle Problem Persists
 

Hey guys,

I've exhausted every common fix, I think, for my 2000 SE Manual.
Maybe you guys can point me to some other ideas.

Symptoms: Idle is always perfect during warm up/cold start. After warm up period it *sometimes* decides to dip to 200rpms, or die altogether. Performing the idle relearn fixes this for another couple hundred miles, sometimes even more, but eventually it decides to die at a stoplight again.

Car has: New plugs, new IACV, new MAF, new PCV, and new air filter

Car gets great gas mileage, has no power band issues of any kind. Throttle response is great.

I can't find any vacuum leaks or obvious bad hoses. After the new IACV, the idle was more consistent, but still went back to dying again a few days later. I assume the IACV did help, but wasn't the root cause.

I've learned to live with the issue, as I can usually get it to idle again by turning it off for ten seconds and restarting. not always. Then when I get home, I do the relearn.

Throttle body? Sensors?

Thanks for all your help

I always go for the knock sensor. I know then I will have also have fresh upper/lower intake manifold gaskets/TB gasket etc. And so I can look over and clean the items removed.

If my knock sensor was going bad I'd have problems throughout the power band. I've replaced a few of those, they are not idle specific. The gaskets are a good idea. I also should clean my throttle body.

To anyone else, I should of stated I have NO check engine light/codes. Any other ideas???

I never said it was bad. I own a few Maximas and when problems become persistent at 120-130k miles I go for the knock sensor only because it's a wear item and it covers all gaskets from the cylinder heads up to the TB. And allows for thorough inspection and and the best cleaning possible. It just happens to be below the intake and while I'm there it's replaced. I'd hate to tear down my work and buy more gaskets.. It's just a thorough procedure minus the BS. I can then verify none of those are my problems and then move to the IACV, TB, TPS... Which you opted for first. Different strokes for different folks.

what about coil packs the 2k is notorious about failing ?

Those would almost certainly throw a code.

Honestly? With that much work, I'd check fuel pressure. I'd also check to make sure some critter isn't nesting in your airbox.

Also, double-check those connectors for corrosion, if they have been stressed, etc, and replace as needed. But then, I am VW-trained, so I have chased more electrical ghosts than most.

You may want to check the fuel pressure. The FPR could be an issue at idle. Also the fuel filter is an easy enough change.

tps thats what mine did

No code if your TPS is on the fritz?

That should be something the Nissan scan tool (not the generic OBDII ones) picks up on. Heck, the ECU should pick up on it, and throw a P-code for the OBDII to pick up.

Thanks for the ideas guys.

Tps- perhaps this is the next part
Coils: already multimetered and replaced a few of those a month or two back (this problem pre dates those and existed during and after their issues)

Fuel pressure/Filter is a long shot. I think I would of seen a driveability issue during WOT or any other usage other than idle. Like hard starts, etc.

I agree, but TPS aside, you've exhausted all possibilities. There was another thread where someone had difficult-to-trace driveability and idle problems. Something else (but not the fuel pump) failed back there, he swapped the sock-type fuel filter in the tank, and all sorts of things cleared up. That's why I mentioned it - when troubleshooting something weird I tend to follow likelihood in cost order.

Doing a seafoam through the booster line is worth a shot

So as an update: I just pulled my ECU for a rebuild. A thorough diagnostic revealed that the computer refuses to keep idle parameters. No vacuum, electrical, TPS or other problems were the culprit. My shop thinks that the IACV took out the ECU (the dreaded ultimate problem).

200 dollar rebuild from a company in California I found on here. Fingers crossed.

I had the same problem... Just clean your TB and everything should be fine ! Just use the proper stuff and be carefull with the TB.

Well beyond that now. TB is immaculate. Problem didn't go away.

If you have a lot of miles on the car, a new fuel filter cannot hurt. They are pretty cheap and somewhat easy to replace yourself.

135,000 miles. I had the fuel system inspected. ECU is in the mail.