rough idle:(

[tenderr]

hey, guys,I'm coming here for help!!! My 240sx vert has rough idle problem recently. Th engine sometimes quit while waiting for the red light, or she vibrated a little bit. This happens more frequently while there's less than half tank gas remained. Just checked in the garage today, they said air flow sensor needs to be replaced, that may cost >600 bucks. However, they cleaned the sensor to solve the problem temporally, but it will come back!so sad now, anybody here has the same experience before? or any comment?thanks alot!!!

[Eikon]

keep an eye on the classifieds pages for people parting out 240's.. . You should have no trouble finding a used MAF sensor for less than $50.

A bad maf would certainly cause problems for you.

When is the last time you did a little tune up? Replace your spark plugs, air filter, fuel filter, etc... Remove your IACV (Idle air control valve) and clean it out with some carb cleaner... chances are it's all gummed up and not allowing the engine to idle smoothly.

Check you air intake tract to make sure all your fittings are tight and you don't have any leaks.

[GoinTopless240]

When is the last time you did a little tune up? Replace your spark plugs, air filter, fuel filter, etc...

Hmm... also how many miles? any upgrades (ie: air intake, fuel pump)... did this just develop? Is this car a DD (daily driver = DD).

The fuel pump also has a strainer that can clog... making the fuel pump work harder...if the pump has some miles it can get a little weak... When you come to a light it might sputter. I had a similar problem and after replacing the fuel pump and strainer the problem went away and the vehicle ran much better.... Eikon brings up the basics... always go the basic way first before diving in deeper. Plug wires etc.... You should be able to find a MAF sensor for dirt with many of us doing swaps we always have parts laying around...

Hope this helps.... and

Welcome to the Vert Boards... if you haven't registered on the sticky at the top of the topics, put your baby on the list.... it helps us determine how many Verts are still on the road...

[94_240sx]

Hmm... also how many miles? any upgrades (ie: air intake, fuel pump)... did this just develop? Is this car a DD (daily driver = DD).

The fuel pump also has a strainer that can clog... making the fuel pump work harder...if the pump has some miles it can get a little weak... When you come to a light it might sputter. I had a similar problem and after replacing the fuel pump and strainer the problem went away and the vehicle ran much better.... Eikon brings up the basics... always go the basic way first before diving in deeper. Plug wires etc.... You should be able to find a MAF sensor for dirt with many of us doing swaps we always have parts laying around...

Hope this helps.... and

Welcome to the Vert Boards... if you haven't registered on the sticky at the top of the topics, put your baby on the list.... it helps us determine how many Verts are still on the road...

Speaking of fuel pump, should I just replace anyway since it's been running for the last 13 years(140k)? Will I see the difference? I know Walbro is the way to go but heard that it's noisy. I wonder what other quality ones available out there and when is good time to replace it. Any thoughts?

MAF sensor is plenty in junkyard, and at least it doesn't sound like injector problem which will cost much more to repair. Yeah, always go from cheap to expensive when it comes to fixing and trouble shooting. I hope you fix the problem soon.

[GoinTopless240]

Honestly my tank was so messed up (rust) that anything was almost an instant improvement... I posted awhile back that it was noisy when I first put it in, but my tank was so so so rusty that the strainer was almost instantly clogged and the extra strain on the pump made it noisy... I've tamed the rust in the tank and replaced a bunch of strainers and fuel filters... I have to say that the noise in only slightly louder than the stock unit... I am going to the SR so it was a necessary upgrade... I will say that at full throttle the old pump seemed to lag a bit, after the new pump the acceleration is more constant. That may have been from the cleaning up of the rust problem.... as for noisy... no not really..

[94_240sx]

Yup! I remember that you could scoop rust out of the gas tank. Glad to hear that noise is not that bad. You know Walbro has a nickname, 'Whinerbro' cuz it's noisy. Anyway, I'll definitely consider new fuel pump since it has never been replaced. I bet the sock is dirty as hell although pump is still working.

[GoinTopless240]

i will say .. I was beginning to get some hesitation off throttle and a bit of an idle drop (blip where it would bounce off 500 rpm and go back to normal) with old pump. Since the new one... nada.. smooth and good on take off.. the old rev sensor is acting up now, so starts from standstill are of an art form to make it shift to second... I unplugged it from the harness, but did not like the way it shifted the rest of the time...esp at higher speeds (bounced in and out of overdrive to easily). I would think almost everyone with original pump would benifit with at least changing the sock... hell it only take like 20 mins.... oh yea make sure you replace the gasket (dealer only part) around the top of pump assembly.. hmm may make a good picture...

[ishkabibble]

make sure you replace the gasket (dealer only part) around the top of pump assembly..

Bosch sells the gasket, also. Maybe Nissan gets it from them?

[94_240sx]

^^Oh! New sig. Gorgeous...

[ishkabibble]

I've also got a Walbro waiting to go in and am concerned about noise. I know some people cover the pump with pipe insulation or a piece of radiator hose and it's supposed to make it quieter. I'm probably going to do something like that, but am going to be constantly paranoid that some crud from the insulator will flake off into the tank.

Thanks 94. Still nowhere as clean as yours I actually got to drive with the top down today - first time in many weeks. At one point, some girl in an S13.5 fastback with CF hood, a 350Z vert, and I were all driving in a row. Weird coincidence. S15 front does not look right on a S13 fastback, btw.

[tenderr]

Thanks all! You are so helpful, thats why I like this forum so much! The bad news is after cleaning, the same problem come back again~ Maybe I do need to replace one. I failed to find used air flow sensor in junkyards nearby, err, anyone here can sell me one? any information helps! Thank you!!

[Eikon]

hey.. we just pulled one out of my brother's car.. the engine was shot.. but the MAF should still work fine.

email him. His screen name is Omnikron

joel.blackman (at) gmail.com

[tenderr]

Thanks alot!!! just dropped him an email

[DeafMonkey]

Hey, I know what youre talking about, I had the same problem a while back.

On the way back home after a 700 mile trip, my car started to act like it was out of gas with a full tank. I was on the freeway going 80, the RPMs around 3k, and after a down shift it started to go crazy. Stepping on the gas didnt do anything and when I pulled off the freeway into a gas station it would idle uncontrollably, between 300 and 1500 back and forth until it stalled out. When I started it back up again it was fine, but after 10min or so it started acting up again.

To make a long story short, I got back home and took it into a shop. Of course, it started up fine and didnt act funny. I figured it was the fuel filter that was the problem (being original, with 145K miles on it) so I bought one from auto zone for $10 and replaced it myself. I havent had any problems since then.

This might be your problem, or this might be something completely different...

[TuRbOS13]

I'm actually having the same problem right now! When i'm stopped at a red light the idle will drop down really low, sometimes to around 300 and the car actually shuts off sometimes the idle gets so low. When I step on the gas I have no problems.........I took it to my friend who is a Master Tech and is a 240 specialist so he took apart my MAF sensor and said he's 90% sure its that.......he said I could get one for $30 used.
Modified by TuRbOS13 at 6:13 AM 7/31/2008

[94_240sx]

I'm actually having the same problem right now! When i'm stopped at a red light the idle will drop down really low, sometimes to around 300 and the car actually shuts off sometimes the idle gets so low. When I step on the gas I have no problems.........I took it to my friend who is a Master Tach and is a 240 specialist so he took apart my MAF sensor and said he's 90% sure its that.......he said I could get one for $30 used.

Whatever you do, always go from cheap to expensive parts.