Running Rich, Stumbling, Stalling

[bslyth]

Okay guys. I'm at a real standstill now, and most of the time quite literally.

A while ago my MAF threw a code after some jerky driving and stalls; I replaced it and it drove fine for a little while. But the problem was not solved.

My issues are as follows:
1. After acceleration (hard or easy) the car begins to stumble trying to maintain the now slower speeds - let's say I gun it to 60 and then come back down to speed limit of 35. The entire car shakes several times and jerks forward/backward a couple times; all is fine after until the next come-down.
2. I can smell gas in the exhaust occasionally when I park, but most often when stalling (air issues?)
3. The car stalls off and on. Sometimes I take a turn and slow down substantially and the car dies. Sometimes I come to a red light or stop sign, and the car dies.

The work done the past few months:
1. new MAF
2. oil change
3. new Spark plugs
4. new fuel filter
5. replaced both Knock Sensors (they've been out on the car since before I purchased it 2 years ago)
6. I took off and cleaned the IACV myself

My best guesses right now are:
EGR stuck
Throttle dirty or TPS not working
vacuum leak

I have not been able to check any of these yet, but if you guys are confident I should check one or something else please let me know. All help is appreciated.

[bslyth]

Did a basic visual inspection of the vacuum lines. None of the rubber seems to be broken, nor the metal pipes.
The Throttle Body is relatively clean. There is a tiny bit of carbon and crap on there but nothing that interrupts the function of the butterfly valve.
I do hear a high pitch noise coming from the engine bay that wasn't there a few months ago (before the problems) which makes me think there is a leak.

In case it matters. 165000 miles - regular oil changes - always warmed before racing.

[skyvette427]

My similar issues were fixed by cleaning throttle body.

So there Check Engine is not on?

[OwnerCS]

What brand of MAF did you use for a replacement? The stumbling and stalling reminds me of a MAF issue with the type that is used in the Y33.

Sooner or later your injector o-rings will start leaking from old age. Failing o-rings and cracked pintle caps will let too much fuel pass from the rail into the intake manifold. Leaking injectors cause flooding and unburned fuel to pass through the exhaust system. I've replaced or refurbished all Phase II injectors on my 98 and 99 model Maximas. The Phase II injectors on a Maxima use the same o-rings and pintle caps as the injectors on a 2nd gen Q45. I'm seeing a high number of leaking injectors and related flooding problems occur with Phase II injectors in Nissan VQ30DE engines in the 1995 to 1999 model years.

Here's a picture of how leaky injectors look. These injectors leaked for too long and caused flooding that eventually lead to the cats to becoming cooked and clogged.



Here's a picture of injectors from a 98 model that I replaced as preventative maintenance.



You can see how the o-rings start to flatten with age in this picture below.

[bslyth]

I had begun to think there could be Injector leaks, but was aggressively hoping that was not the case. Next time I have some cash flow or time I'll check em out.

No Engine Check Light.. And the MAF was a generic replacement from Napa I believe. Could possibly figure out the manufacturer

[Q451990]

Non OEM MAF doesn't give me warm and fuzzy feelings, but hopefully it would throw a code. That high pitched noise seems like your best clue. Might be worth spraying some brake parts cleaner around that area to see if your idle speed increases, indicating that the fluid is being sucked in and burned as fuel. Ditto on Craig's thoughts on injectors as well.

[bslyth]

So I found some time to stick my head under the hood. Found one vacuum tube disconnected... BUT that didn't fix the problem, although the high pitch noise is gone I think (air whistling into the metal pipe?). After that though I now have a check engine light, which is hopeful yet dreadful.

Sprayed some cleaner on most of the pipes and tube fittings, but haven't sprayed across rubber yet. That didn't come up with much.

I have to get some tools, but I'll get a look at the injectors once I do.

[Q451990]

Have you pulled the code from the check engine light?

[bslyth]

Yes, just did.

Originally it was MAF and KS2, but I had started the engine yesterday with the MAF unplugged on accident.

Cleared codes, started the engine, revved to about 2K, and BAM comes KS2 again. I just replaced both of those so I ought to go talk to the mechanic about that.

And of course, it almost stalled while starting it. I've noticed it idles around 700+ no matter what I do to the idle speed control. And then when stalling it butterflies between 350 and 600 trying to stay alive.

[EdBwoy]

What is the KS2, is that a code in itself or an object related to a Pxxxx code?

[HansCC]

Coil Pack Replaced? you can use Hitachi

[HansCC]

Did the coil packs get replaced? you can use Hitachi

[bslyth]

Did not replace the coil packs.

KS2 is knock sensor 2. I don't remember the exact PID

Went to the mechanic a few days ago. His quick analysis before we made an appointment was a vacuum leak is still present somewhere as the whistling is not completely gone; there may be an air tube out of sight somewhere that was not accounted for. He also believes the vacuum leak could inspire a knock sensor ping, so the plan is to get the breathing right before taking the manifold off again.

Of course, just my luck my car won't start. Battery indicator light is on. I've charged it and it starts but soon dies (SCREAMS ALTERNATOR), so later will be getting electrical system checked.