"Bobbing" Idle

[Antjaw]

I'm sure the answer is out there with the search button but it pulls a million responses.. so cut me some slack.

Heres the deal.

When at a dead stop, the engine drops from normal idle of about 800-900 down to about 300-400 and bobbles a bit then bumps back up to normal.. It continues to do this hot or cold.. doesnt matter.

It just started doing this.. no changes have been made to the engine what so ever.

The only thing I can think of is as follows: I pulled out in front of a truck.. I guess he thought it would be funny to ride my A$$. So I decided to just floor it and leave him in the past. I VERY rarely press the gass pedal to the floor. As I hit about 6000rpm in 2nd gear, I looked in the rearview to see where I left him and I saw a BIG puff of black smoke as I shifted. The car never smokes durring normal use though.

It just seems the rough engine started after this.. maybe it has somethin to do with it.. or maybe its the 150,000 miles catchin up with it.

Thanks guys.!!

[p00t]

I too do have that idle problem... tho its not too severe... it dips down to 500 with the brake engaged and 750 when not.

Black smoke indicates a rich fuel to air mix. So its possible under high rpms your intake isnt keeping up. Possibly something in the intake is clogged or its airflow is restricted. Thats my guess. Hopefully someone can help you a bit more.

[MaineExport]

If you rarely push your engine it isn't unusual to burn off some filth when you hammer on it. That MIGHT explain your black cloud. It could also be MANY other things... but not likely.

The irregular idle might be as simple as a MAFS in need of cleaning, or a dirty air filter. Start with those and if it persists... go from there.

[Bryson]

It could also be the Idle Air COntrol Valve being really dirty, this causes a similar situaiton for many people, I made a post a day or two ago explaining how to take it off so you might wanna look for it. Like maineimport said though, could be MAFS or air filter, I need to check those on mine because cleaning the AAC vavle helped, but didn't completely fix my problem.. mine is more like yours now.. it dips down now instead of almost always dieing.

[Antjaw]

Is there any chance it could be the O2 sensor?...Maybe when I pumped all that black smoke out...it coated it in carbon soot or something.

[nightshift]

shhhhiiiitt . . . .Ive had that problem as long as Ive had the car it seems to me it will never go away but mines only does it once in a while it use to die liky bryson mentioned . .

I dont know what will fix it but I can tell you that after going through all my intake components changing the o2 sensor, the fuel filter, cleaning the AIV, AIC, and the rest of the alphabet that I could get to, adding fuel injector cleaner and a crap load of other stuff the only thing that made a drastic diffrence (the car doesnt die) was I got some electrical component cleaner and soaked the S hit out of every electrical connection I could find in the engine bay and then spent the rest of the day wiping and drying, the next day it worked perfect and then it started doing it again but it doesnt die it just does that stupid idle bob but its not that severe anymore either.

[PapaSmurf2k3]

cleaning the AIV, AIC, and the rest of the alphabet that I could get to

Yeah no kidding, how many crazy valves are there in this motor, and how many of them are useless and can be removed without screwing anything up (I like simplicity). One of these days im just gonna stock up on carb cleaner and electrical cleaner and just start unbolting stuff without a gasket one thing at a time and cleaning the living crap out of it. then and only then will this one little problem that everyone seems to have go away:evilhaha

[Antjaw]

then and only then will this one little problem that everyone seems to have go away:evilhaha

I didnt realize that this was such a wide spread problem. Maybe I should just take it to my mechanic and have him fix it and tell me what it is.. he is a Nissan GOD.:icesangel

[L0sT]

im kinda a newbie so lol..wuts..EGR?AIV?AIC?AAI? and so on...

i have the same idle problem, when i first start the engine, it will go up to 1000 rpm, then drop fast down to about 200-300 rpm, then back up again...and sometimes when it goes down, it just DIES!! sometimes though. and also when im at a stop, the rpm needle bobs up and down, 1000 down to 200 and etc...the car also shakes alot while this happens..and i can also sometimes hear a popping sound coming from my exhaust, i got a hayame exhaust.I NEED HELP!k tanx

[nightshift]

I inherited a Hayame exhuast from the previous owner . . . maybe its the exhuast? lol

[Antjaw]

Anyone have a comment about the O2 sensor?

[PapaSmurf2k3]

Well, my car does it, and i recently did a full tune up. plugs, wires, cap, rotor, o2 sensor, fuel filter is new, ran some fuel injector cleaner through it. alls all that did was set me back some bucks, so i doubt its the o2 sensor.Antjaw- feel free to take it to the mechanic and be like "fix my idle problem and tell me what it is, a lot of people have it but they are too lazy to go testing and troubleshooting every little thing". then let us know

[s0ldats]

aggghH!! i wanna fix this gayyy problem.

[detforme]

i had the same problem so i looked for a vaccum leak. Its not the easiest thing to get to but the egr solenoid is located on top of the intake manifold collector. There is a screw that goes through the platics side and out te metal. To kepp it from leaking they used an epoxy type glue on the nut and as it gets old it cracks and leaks. Its really hard to get to. you must take the manifold off to get to it. without a large assortment of tools you probably wont be able to get the manifold out.

[PapaSmurf2k3]

maybe ill throw a carburated 350 in there, no computers, no crappy valves, just carb, throttle cable, transmission, and driveshaft= bawlz to the wallz w/ no exhaust

[Queamore]

maybe ill throw a carburated 350 in there, no computers, no crappy valves, just carb, throttle cable, transmission, and driveshaft= bawlz to the wallz w/ no exhaust

Got it in the 75 malibu. Raw power baby YEAH!

[skydragoness]

hmm. the notorious idling/hesitation problem that never seems to go away on this board.

i have the same thing. car doesn't choke off, but it dips, and when it does it shudders. and going throught the gears there's a hesitation after 2kRPM and then keeps pulling like normal. i do have a clogged catalytic converter, that i will be replacing soon, which could explain things. and i'm also developing a slight valve tap, but anyhow. i do believe the problem with the idling fluctuation lies with the AIC valve, or the EGR.

now as for getting around to fixing it.. hehehe

[nightshift]

scratch the cat . . . I dont have one . . previous owner took the liberty of removing the whole exhuast system fromt he manifold back and welding on his neighbors fence

[Antjaw]

I am just gonna spent the cash and take it to the "Nissan God" in Jacksonville, FL known by Japanese Specialist. I will post the results when I get her back.

[Antjaw]

Guys.. I know I dug this one up from the past.. But at least I have a resolution...No one could figure out the problem.. I was lookin through my local coupon mag and noticed a deal on fuel system cleaning at (brace yourself) Jiffy Lube. I said, I need an oil change, so what the hell. They ran this crap through the injectors that made black smoke pour out of the tail pipe.. anyway, when it was done, my car ran like it was new..No more bobbing idle.. back to 25+MPG..my acceleration is back.YEAH!!Who would have thunk that Jiffy lube could fix the problem??

Anyway guys.. CLEAN YOUR INJECTORS!!Hope it works for you 2!

[Axel Grungy]

yeah i used to work at jiffy lube and we did it to my 91 integra and it ran alot smoother, and my gas mileage was back up a bit. SOOOOO much crap came outta the exhaust it was insane, all the other stores around us thought the building was on fire.

ps. dont breath in that crap....very bad

[180fan]

Well I had a stable idle until a few hundred miles ago. I've got 163.5k on my motor now. I pulled off my IAA and cleaned that out, helped a bit initially but now it bogs a bit further. So I thought maybe cleaning out my intake manifold would help a bit more. I've yet to go back to clean it again. I have a feeling it could be my AIV, but it's strange since I cleaned it not too long ago, but then again it doesn't have a filter on the aiv now. The only other thing I could think of is to check the pressure regulator to make sure my fuel pressure is ok. I checked the fuel filter by popping off the line just before the intake manifold, and it's comin out clear. The other thing you might want to check is your injectors. I think I'm gonna go grab my buddy's injectors, have them cleaned and blueprinted and then cram them in mine. I've also added some grounds, but for now I'm dealing with a high idle so it doesn't dip as far down when I go into gear until I figure this thing out.

[Antjaw]

Sounds like your rollin in the right direction.. Just one note.. Just because the fuel is comin out of the filter clean doesnt mean you have a clean filter.. It may be so clogged that your pump cant get enough fuel through it.. The only wat to truly know is to replace it.. I think its only like $15 bucks.. as much as I hate throwing parts at a problem.. I would rather em be cheap parts... Good luck Buddy!

[lbrowne]

Wonder how much this fuel system cleaning costs at my local Lube X (same as jiffy lube)

I'd like to get it done when I bring her in to get her rear diff fluid changed.

[Jim_A_B]

The "black smoke pouring out the tailpipe" treatment sounds just like pouring SeaFoam ($6 from Napa) down the brake booster vacuum hose!

[180fan]

Yeah I think it's time to try a new fuel filter and probably a new fuel pump would be a good idea since I'll need that when I do get around to my SR swap later this year. Hmm maybe while the car's under the kinfe, it'd be a good time to clean out the gas tank too. Well we'll see what happens. Ha ha ha. Again I'll keep you guys posted on possible solutions to the pos idle on my car.

[Antjaw]

Jim_A_B........I think it is exactly the same as the seafoam treatment.. dont know which is the higher quality.. But it was the brake booster line that the pumped that stuff in... I ended up paying 60 bucks for them to do that.. which is fine cause it fixed my problem.. But I know that they made about a 58 dollar profit on me.. They just used half a can of this stuff... Jiffy lube brand.. couldnt have cost them that much. But hell.. its cheaper than the new engine I was ready to buy to fix this darn problem.

[180fan]

damn. alright that sounds like a plan then. I guess i'll have to drive out to the ghetto area (only place in my area with a Napa auto parts =( ) to get some of that seafoam stuff. I found something out though, the low idle comes in only when I start my car now and only if I don't press the gas. If i press the gas then the idle will be fine. It's a strange little bugger I tell ya.

[180fan]

Well your battery problem sounds like something I had before too. The - terminal and the stand for the battery were totally corroded. So what you may want to do is change the grounding wire with 4ga and ground it somewhere else. The ground cable does also link up to your engine and the tray your battery sits on. So you may want to daisy chain it to somewhere else on your chassis. Worked pretty well for me before. Oh yeah it was the injector, it was sticking when it first starts up. So what I had to do was give the git a bit of gas to free it up, but after I got the injectors pulled and cleaned, works quite well.

[bvanev]

A friend of mine was having the same problem with her 240. I originally had the motor that is in her car, I installed it in her car after I bought my SR. When I had the KA it ran fine. About a year later she starts having major idle problems, so bad that she had to raise the idle to 1700rpm to keep the damned thing running. When I got a chance to check the motor out, I found a faulty MAFS (did not trigger the ECU into fail safe mode), broken O2 sensor (the bulb was shattered), a dirty air filter, and a completely clogged fuel injector. ALL IN THAT ORDER. The fuel injector was the biggest problem. Her car never let out any black smoke, but all of the seals where good in that car.

With my SR I currently have the following problems and symptoms. Extremely low idle, 500-600rpm, idle hunts and will stay running (after an upgrade in plugs) even under load. Gray smoke (combination of black and blue) caused by fuel in the oil, reducing the viscosity to near that of kerosene, this allows small amounts of fuel and oil to seap by the piston rings and be combusted, resulting in foul smoke. The fuel got into the oil by means of a faulty fuel pressure regulator. The diaphram broke and as a result left me with insanely high fuel pressure, causing a very over rich mixture.

I plan on fixing my problems by:1. An oil change2. Idle screw adjustment (fully closed at the moment)3. Ignition Timing adjustment.

Hope this helps.