Car problems - Idling leads to engine chugging

Henroid

Over the last couple of weeks I've noticed a problem with my car that seems to be getting worse with time. Whenever I have the car stopped the engine chugs. Usually when I'm at a stop, it idles at just under 1k RPMs. And it does for the most part, but then it clicks and the RPMs drop to about 500 RPMs, bouncing barely over and barely under, for a few seconds. Then it clicks again and I'm back to idling normally. The problem doesn't really happen if I'm set to park, it's really subdued in that case. Otherwise, when I'm driving it's totally fine. So does anyone know what could possibly be causing this? I don't run the car low on gas, by the way. Earlier this year, we had the fuel injection and the distributor replaced by the dealer. That's the only work done on the car in any recent time.

Also I'm making a thread of this instead of going to a mechanic or whatever because I'm specifically trying to avoid paying 1) for a diagnosis and 2) a bullshit diagnosis and 3) a bullshit diagnosis and someone going ahead and starting work.

Skoal Cat

First guess is that your spark plugs aren't firing right. Could just need some new ones.

Daenris

In addition to spark plugs, it could be the idle air control valve or mass airflow sensor. Depending on the car they're usually pretty easy to clean.

The Black Hunter

Go to a mechanic and get a tuneup. Tell them to contact you about any replacements over $50

spending $400 now to get it in bang smack condition is better than needing to buy a new car and sending this one off for $90 at a scrap yard.

If you got the injector changed over it probably needed to be run in, and upkept in good tune.

Bendery It Like Beckham

What is the make and year of the car?

Well, order of least costly to most costly.

Air Filter
Spark Plugs
Spark Plug Wires
Fuel Filter
Timing (you had your distrubutor replaced, so if your timing was retarded or advanced it could wonk your idle on occasion)
Engine Wiring Harness (very very unlikely)
Idle Control Valve
Mass Airflow Sensor

What I would do is start by changing the air filter, then checking the wires to make sure they are completely snug from distributor to engine. When was the last time you changed your wires/plugs? Air filter doesn't do it, time to change the wires/plugs if it's been a while. Chances are it wont be the fuel filter, it's uncommon to mess with your idle unless it is clogged, but you're not stalling. Timing is an unlikely candidate but possible; you'll need to go to a shop to have it checked.

If your wiring harness isn't making contact 100% of the time to your ECU it can mess with various things, but this is only common in engine swaps and custom ecu jobs.
ICV could be slightly loose, depending on your car you may be able to tighten the valve with a hex wrench consult youtube.
MAF sensor is the sensor normally connected to your throttle body, it's the one that is not the throttle position sensor (they are normally the same type of sensor wired to different parts of the ECU, consult your manual or the internet to find out which one is which).

Thats a good place to start, any other behavior? Do you have enough water in your radiator reservoir? Your ICV is controlled by engine temp read by fluid from the radiator, so if the fluid is too hot because the reservoir is low this could also create a problem.

L Ron Howard

Do you get a check engine light when it happens?
If you do, you should just take it to Autozone and get them to do a free diagnostic scan on your car.

Henroid

The timing issue is something my stepdad brought up, but I don't see how it could be an issue if the actual manufacturers did the replacement (it's a 2000, I think, Nissan; they have a place in town). Unless they just screwed up by chance. They said they've put us on warranty, at least with regard to the replaced parts, so that should mean they'd be willing to look at things without me having to pay out for it right? I hope? Maybe?

Edit - And no, there's no check engine light coming on.

Henroid

I dunno if this counts as necroposting and I apologize but there's plenty of updating to do.

L Ron Howard wrote:

Do you get a check engine light when it happens?
If you do, you should just take it to Autozone and get them to do a free diagnostic scan on your car.

I get a check engine light now, over the last week and a half. I just got back from the dealership (it's my first real chance to get the car over to them; I'm not the owner of the car, so I can't make decisions on how to fix the fuckin' thing without consulting that shit (long story)).

The guys at the dealer said that the intake manifold gasket is leaking, and what's causing the car to start to want to die any time I'm stopped. They also identified a separate unrelated issue that's not as critical (the valve cover gasket is leaking too, said that oil leaks a bit because of this).

Here's the thing - To fix it all, cost of parts is like $50 to $60. But that doesn't include labor. To fix the intake gasket it'll be like $760, and the valve cover gasket would be $290. I've been instructed to start calling mechanics in the area to see what they would charge to fix that shit, which has me nervous as shit that they're going to fuck something else up.

Donovan Puppyfucker

Changing intake manifold gaskets is easy as piss. It sure as hell isn't $760 worth of labour (what is that - 10 hours?!?). And the rocker cover gasket? Half an hour, MAYBE 45 minutes. So $290 is too much for that as well.

Henroid

I forgot to mention the fuckers charged me $105 for taking a look at the car and diagnosing it.

Donovan Puppyfucker

That's pretty much standard.

Bendery It Like Beckham

Changing the intake manifold gasket is super easy. Buy the part and hit up youtube.

Henroid

Bendery It Like Beckham wrote:

Changing the intake manifold gasket is super easy. Buy the part and hit up youtube.

You mean like this?

http://www.youtube.com/watch?v=0huAd-CusBo

Honestly, while I don't know shit about cars I am pretty mechanically-minded, and the idea that this is nearly $800 in labor is goddamn insanity. I'm in the wrong career field.

L Ron Howard

It'll take you a good day, if not two, if you're doing it the first time. If you pay attention to the video, it probably took him a good chunk of the day as it is.

Donovan Puppyfucker

And he put the new o-rings on the bottom of the manifold, then flipped it over and sat it on the asphalt. Yeah, that's really good for the rubber o-rings. Also, dirt. You dumb shit.

Henroid

This is why you guys are here to tell me these things.

Bendery It Like Beckham

Yeah, that's basically it. Keep in mind that intake manifold is to a ford, so it's plastic. It's also to an 8 cylinder. Fords are hard to work on because their part placement is just silly sometimes. Nissan should be easier depending on year.

Edit: I guess some anecdotal evidence is when I first started getting in to car repair I changed the intake manifold gasket on my Honda in ~2 hours. A breaker bar is going to make things substantially easier for getting the manifold off, just take a bit of pipe ~3 feet long and attach it to your ratchet (or preferably a proper breaker bar just in case... I've broken a few ratchets with a "cheater bar")

L Ron Howard

Yeah, I didn't want to mention the whole putting the clean engine parts in the fucking dirt.

Henroid, if you have a 4-cyl engine, it will be easy as hell. Everything should be pretty easy to access.
If you have a V-6, it will be so much harder, as half of the engine is going to be hard to reach because the bolts in the back are going to be really hard to reach.
V-8's aren't too bad, but the last couple of bolts in the back are a pain, but I doubt you have any more than 6 cylinders.

Donovan Puppyfucker

I think the Xterra has a 2.4 four cylinder.

L Ron Howard

My English am good, no?
I meant to say that the back cylinders of V6's are usually tucked behind and underneath the cowl (where the vents are up top, with your windshield wipers). They are hard because it's almost always a very tight fit to get your hands back there, let alone a wrench with an extension.
But 4 bangers are awesome.

Pel

I doubt an intake manifold would require serious ability to remove even on a v6: typically the intake lies between the heads and dead in the middle of the engine compartment, and the plenum leans over forwards or back. If it's the 2.4l 4 then it should be pretty simple regardless, I had an Altima which I think had that engine and as long as you take lots of pictures of what you're doing and have someplace to work on it, you can do it yourself. Buying a set of basic tools for the job will probably save you money in the long run. My advice would be to find a Nissan/ Xterra enthusiast forum and ask there for advice before you start, though. Every car I've had, I've joined an online community based around it and typically they are the most helpful and knowledgeable groups you will find. Often there will be lengthy guides for most commonly encountered problems, and a multitude of posters willing to give newbie-friendly advice.

Donovan Puppyfucker

The absolute best resource for any car will always be the factory workshop manual. If you can get one, then do so. Sometimes they are reasonably priced, sometimes they are exorbitant, but they are always worth it.

Henroid

My car is a Nissan Altima, 2001. It's a 4 cylinder engine.

My friend at work told her husband about it and he's gonna drop by to help me out with it since he's done this before. I think this is case closed here. Thanks for all the input you guys.