All research does is make me more confused!

I'm considering 1/3 in the fuel tank, 1/3 in the oil, and 1/3 slowly poured in the Brake Vacuum Hose with the engine running and NOT choking it out. Turning off the engine and then let it sit 30 minutes. Then restart and smoke. Almost 218K.

JHolley in 2008 said in a post, Seafoam cured his Maxima of that sitting in Idle with the brake on at a light, stumble that is annoying as Dung!

I refreshed EVERYTHING on the entire Intake and it's still there.

Please share your experiences!

Don't use it in the oil, it's a petroleum product similar to gasoline and can fuel wash your bearings. My own vehicles right before I change the spark plugs out, I just use an adapter to the brake booster hose to attach it to a smaller diameter hose and let the smaller hose suck out the seafoam over a 5-10 minute timeframe into the intake then attach the vac hoses again and rev it to make the smokeshow. I just toss half a bottle of marvel mystery oil into the fuel tank as well. For adding something to motor oil, about 1000 miles before youre due for an oil change you can drain 1L of oil and add 1L of auto transmission fluid to the crankcase. It has detergents that will clean out engine internals, i've done all of this for years and even my high mileage engines the internals are spotless

Keith,

To be completely honest, I’ve tried pretty much everything over the decades … Seafoam, TCW3, MMO, Lucas, Liquid Moly … pretty much everything at some point.

My sincere advice?

Don't use any of them.

Just do regular and routine maintenance.

But,
But
But, That Efffin STUMBLE at a light, in drive, with the brake on!

Thank YOU!

Your car has all the symptoms of a simple
vacuum leak.

Keith,

It sounds like a couple of additional/other culprits might include:

- a malfunctioning or maladjusted throttle position sensor;
- a worn or failing intake air temperature sensor;
- as always, a dirty or old MAF.

Maybe have a look (if you haven’t already) at the accordion tube and the baffle box assembly between the MAF and the throttle body.

I did the IATS the last time you suggested it in the past year. And the TPS right before that. Even a new IATV.

I have 3 MAFs here. The last one that I bought recently was from JHolley with low mileage. All have been cleaned and swapped out. And the accordion hose is in good working order too thankfully.

JvG, unfortunately is probably right! Built a smoke machine and found the big leak. Looked at as much of the vacuum lines as I could see, and replaced most. Propane through a tube by all the gaskets in the Intake too.

Over the years, so many have posted about the stumble and always the same responses. The only one that I saw that followed up with a positive outcome was JHolley using Seafoam.

Burl Ives had a Christmas song back in the 60s.... Silver and Gold. One day, I'm going to change the words to Fire and Theft. LOL As the flat spot on my forehead grows ever increasingly larger!

But when in Park or Neutral.... A smooth as a _______. use your imagination

Ya know Keith … I know that a Ford 351W matched to a Ford E4OD auto-trans doesn’t have much in common with a factory 4th generation Maxima combo, but the Ford setup will sometimes exhibit a symptom of stalling and/or rough idle when shifted into R.

Having ruled out other possible contributors, the cause of this symptom is typically a dislodged or fallen off auto-trans filter that’s fixed by draining and dropping trans pans and reinstalling the trans filter.

I wonder …

I guess I should remove the Ford transmission and put the Maxima one back in?

When I said "use your imagination", I probably should have put some parameters on that? LOL

Does it having the A/C on change anything?

The idle increases a little and less power accelerating! Stumble is the same.

I'm replacing the S2 O2 sensor by the firewall (Bank 1) tomorrow. The O2 sensor stays on one voltage while all the others are constantly adjusting as they should.

It's been 15 years so I don't recall how I fixed the stumbling idle? As others have noted I now stay away from seafoam. For engine cleaning today I use BG109 engine cleaner. I get it for $19 on Amazon. After warming it up for just 10min you need to empty the oil. You'll get black crud in your oil pan.

Another better cleanser is MOPAR CCC (combustion chamber cleaner). The foam expanding cleanser reaches further areas than liquid cleaners. I last got a can at the local Dodge dealership for $25.

Keith.....
You mentioned that the car dies not stumble in park or neutral.

Let's try an experiment.

1. Engine should be at normal operating temperature.
2. Note rpm in park or neutral.
3. Move gear selector to Drive position. Note rpm
4. ( the actual experiment) raise rpm in drive to the rpm it has in neutral. Does the engine feel the same as in neutral. I mean the missing issue.

Experiments? Hmmmmm..... Very Interesting!
Park or Neutral all warmed up: 750.with up to +/- 25
In Drive: 625.... +/- 25......
with giving a little gas to 750... Better, but not smooth like Neutral.
Funny, No more Swirl Valve codes after replacing the B1S2 O2 sensor. Who'd ever think?
Also NOTE.... This is the lowest I can get the RPMs to with the IACV adjustment.

I have to be missing some sort of vacuum leak. What if the EGR valve is stuck open all the time? Would it definitely throw a code? It would explain why Propane by all the usual suspects didn't change the RPMs.

There also looks to be a vacuum hose to the Cruise Control unit. But when I pull it, there's no vacuum. Does that only happen when it's engaged driving?

Thanks JvG! Hope all is well and moving forward!~

I agree with Turbobink.. routine maintenance is best, the so called “cleaners” don’t do much and I’ve actually had components crap out from using them.

- air temp sensors Nissan oem are inexpensive on eBay
- using MAF cleaner doesn’t always resolve issue even after proper steps taken (letting dry).. worth a try but MAF sensors are fairly inexpensive at junk yards..

Could be:
- o2 sensor
- fuel line
- fuel pump
- fuel pressure sensor (the fuel intake/near fuel injector line)
- fuel filter** <definitely>
- PCV valve clogged (throttle body cleaner/brake cleaner dissolve build up)
- EGR valve (bottom right engine, near top of trans, have to disconnect large metal rail or jimmy-cut studs to remove egr pipe plus actual EGR)
- fuel injectors (must get oem, aftermarket requires full tune)(make sure to get new gasket/rings)
- spark plugs, bad Gap or not tightened to spec
- coil packs (must be oem, 1 of 10 after market will resolve misfire)(must swap all six or no solution)
- valve cover gaskets
- intake plenum gasket (not sitting correct or old/brittle)
- head gasket
- cracked crankshaft (due to forced accelerating and delay trans shifting) (- can cause drive train issues: axles, power steering fluid/parts)
- one or both crank position sensors (front and back)
- a/c compressor and or a/c components (a/c into cabin/heater core/cabin radiator thing)—>(there are components involved with engine cooling which helps engine compression, timing, ECU things)

sure, it could be a vacuum leak… but if you’ve tested and resolved the majority of leaks, replaced/cleaned other parts like the IACV… it’s time to branch out to observe if something else can be the issue.

I’ve had three 4th Gen. maximas, numerous different issues and some the same.

Edit: sorry, haven’t read all of your posts / problems.. definitely check the transmission fluid and consider a trans fluid/filter service.

Wish I could say THANKS with that wild goose chase list with some things on it almost laughable, And never brought up here with the newest 4th Gen being 24 years old. That's a lot of years to never be discussed and most likely not a 4th Gen weak spot. And if did happen somehow, wouldn't be running smooth in Neutral.

There's a MUCH smaller list when the lowest I can get the RPMs is 750 and they all have to do with air getting into the intake some place it's not supposed to. That makes the ECU add more fuel by the O2 readings that squelches what the MAF is sending. If no extra air was getting, I could easily drop the RPMs to below 500 with the usual adjustments.

I also did the ENTIRE Intake Refresh less than 500 miles ago.... EVERYTHING! And done with all the best available parts and rebuilt JECS Injectors.