Hey guys, I'm Mark.

As you could probably tell from the thread title, I'm new around here and need some help diagnosing the main issue with my (stock) 5-speed SR20 powered 2000 Sentra SE. I apologize already if, in my noobiness, I posted this thread in the wrong place, or broke some rule of SR20 etiquette. If I did post this in the wrong place, just let me know how to move or fix it.

Anyway, down to brass tacks...

For a while now (a bit over one year), my car has been having two separate, but related issues.
1.) Idling low and stalling
2.) Losing power and bucking

The first problem that appeared was the idling low and stalling. This problem presents itself mostly when the engine is warm and I've been driving for a while. For example, when I get off of the highway and stop at a red light. This isn't a huge problem, as I have adapted to it by heel-toeing the brake and gas at traffic lights, stop signs, or any other time when the revs are apt to drop.

The second problem presented itself more slowly, but has lately progressed to the point where the car almost isn't drivable.

It is definitely the worst when the car is cold. You have to wait until it warms up for about five minutes before the engine will even rev past 3000 rpm while in neutral (forget about trying to put it in gear while it's cold). After it warms up, you can drive it, but you have to accelerate extremely slowly. EXTREMELY slowly. Like, way slower than would be considered safe, even on a desolate side street. If you give it more gas than it likes, you loose power and the engine will slow down (even if you give it more gas) and it feels like the gas tank is filled with chocolate pudding (which would be delicious, though not terribly useful). At that point, if you don't come up off of the gas, the car will start to buck back and forth like it's being driven by someone who has never before attempted driving a manual transmission. As of a few weeks ago, getting on the highway is tricky at best.

Around the time it got really bad it was throwing a code for the O2 sensor under the car, right before the catalytic converter. We checked the sensor and found that it was literally 100% disconnected. All four wires were completely snapped. Hoping that was the entire problem we threw in a brand new sensor. It improved a bit and stopped throwing the code. The problem is still there though, and driving the car is still a chore. This was about two weeks ago.

Repairs / Attempted Remedies:
Cleaning the idle air valve (slight improvement)
Clutch (no improvement)
Injector Cleaner (no improvement)
Exhaust system, minus the catalytic converter (no improvement)
O2 Sensors (moderate improvement)

We checked the spark plug cables and they seemed fine. We have new spark plugs we plan to install (hopefully today).

Well, that was probably way more info than anybody wanted or needed, but I figure too much info is better than too little. Any advice or help would be tremendously appreciated. Thanks, everybody!

Have you taken it anywhere to pull codes of the ECU. It has been quite awhile since I messed around with a B15, and I'm not sure if their ECU has a self diagnostic mode with flashing LED indicator like our B13's have.

Judging from your symptoms I would say its possibly your Engine coolant temp sensor. Its about a $20 part and can be a bit of a pain to replace, due to its placement (AC lines get in the way, it's nestled under the intake manifold on the pass side).

Have you taken it anywhere to pull codes of the ECU. It has been quite awhile since I messed around with a B15, and I'm not sure if their ECU has a self diagnostic mode with flashing LED indicator like our B13's have.

Judging from your symptoms I would say its possibly your Engine coolant temp sensor. Its about a $20 part and can be a bit of a pain to replace, due to its placement (AC lines get in the way, it's nestled under the intake manifold on the pass side).

Thanks for the help. My check engine light has probably been lit continuously for the last year, throwing off the same codes:
Bank 1 Lean
Bank 1 Rich

Both codes have been coming up simultaneously every time, not individually on separate occasions. It thought I was simultaneously rich and lean.

The time I mentioned where the car was at it's absolute worst was about two weeks ago. I was driving down the road when it started bucking like crazy and my check engine light went from steady-on to flashing. After about a minute, the light stopped flashing and went back to its usual steady-on.

We took the car to auto-zone, and found that it was throwing only one code, and it was for the lower O2 sensor. That's when we found it was disconnected and had it swapped. Moments after the sensor was replaced, the check engine light turned off, and for the first time in about a year the car isn't throwing any codes.

typically, the IAC sensor is the culprit.

Nope MAF, guarantee it. It wont throw a code and sometimes it will.

These cars came with bad MAFs I was in denial for 2 years. Finally crapped out and was barely driveable. Reground it and replace the MAF

yep nx$paniard is right

I think it actually both. The idling and stalling issue is the IAC. I just did a motor and 5sp swap and am having the stalling at stop lights and signs. For this you would need to adjust the IAC. For the MAF issue, the jerking and bucking are usual signs of a bad MAF. If its slow to rev or if it doesnt rev past 3000 rpms, then its in limp mode

You should probably pull the transmission and ship it to me. That would fix it. Lol.:biggthump

Been there. It's either the MAFS or Intake Hose... Threw bank 1 codes all the time... I replaced 02 sensors multiple times... Plugs many times... Wires... Then I replaced the MAFS and it stayed off for about a week (The longest it stayed off in a while at the time) then it came back on and the rubber hose from the MAFS to the intake manifold was eaten by heat and oil and had pin holes all in it... Take it off to inspect it. From the top mine looked fine. It was bad on the underside. I think your in the same boat.

You get bank 1 rich/lean codes from Actron equipment for VACUUM LEAKS as well. They generally "assume" o2 sensors.

Post again and let all know if that's it.

I've had this problem with a 91 Ford Ranger. 04 GT and my SE-R

Thanks for all of the replies. I've been out of town for about a week, but checking up on this via mobile. I'm going to try going down the list of suggestions and tackle them one at a time. This problem will be defeated!

MAF!!!!!

Howdy Mark,

I think I'm going to agree with NX$paniard here, my list would be:

1. MAF - reground and test. I've read multiple places that the B15 mafs are known for taking a crap more frequently than is acceptable. Could he upgrade to something like a Z32/N60/N62 MAF? Either way, I've seen B15 MAFs in the classifieds section. There's some guy with like 20 MAFs for all kinds of SRs for sale in there somewhere.

2. Vacuum lines/hoses - check for leaks.

3. IAC - inspect and replace if necessary. Not sure how, as my B13 doesn't appear to have it.

Best of luck and keep us posted.

Blah I have the same issue with the stalling at lights and stop signs on my 2000 SE.

I've narrowed it down to the MAF or IACV but am not sure how to rule out one or the other.

Someone on g20.net said that if the IACV harness is disconnected that the sensor needs to be reprogrammed per a reset procedure outlined in the FSM. I tried that but it didn't help at all. Can that sensor be cleaned and if so, HOW?

Nope MAF, guarantee it. It wont throw a code and sometimes it will.

These cars came with bad MAFs I was in denial for 2 years. Finally crapped out and was barely driveable. Reground it and replace the MAF

I'm late but I second this. Same problem when my MAF went.

OK I went out and tested my MAF today and from what I can tell the voltages are within the working range per the FSM. The next step was to try to clean the IACV. I removed the blue sensor under the throttlebody thinking that was the entire unit lol.

Anyway I ended up removing the throttlebody to pull that and the IACV off together since I couldn't reach some of the screws but I couldn't get the vaccum lines off of the IACV. They are wedged in there pretty good. I'll make another attempt at it but from what I can see, my intake manifold is dirty like hell.

There is black soot all up in there as well as on the back of the butterfly flap. Can I use air intake cleaner in there?

This is the issue I have.
http://www.youtube.com/watch?v=aZZTgWPSp70

Ok I literally just finished putting in a replacement MAF on my 00 SE. My replacement came from a 3.0L Maxima [2000-2001]. From what was posted on B15Sentra it's the same part just a different part number.

It plugged right in and as soon as I started the car everything seemed normal. I warmed it up and the car idles normally. The RPM no longer dips randomly nor does the motor want to stall out.

I'll give it another few days of driving and see the results but so far so good.

its fixed dude... I had to reground my maf....so that may be something worth doing otherwise, you should be good to go.

its fixed dude... I had to reground my maf....so that may be something worth doing otherwise, you should be good to go.

My MAF was regrounded years ago lol. It goes from the connector straight to the battery terminal. :biggthump


Now I just have to fix one more problem-the stupid rattling sound coming from my SSAC header. It's not hitting anything-I think it's the flex section itself because I only get the noise at WOT and around 3K during normal acceleration.

So it's been a week since I swapped out the MAF and the idle is still steady as it should be. No more idle drops or stalling.

I didn't even have any MAF codes prior to this as said above.

My stalling issue is definitely solved.