Question about Horrible Idle

Website · Post by **93Twiztid240** » Sun Mar 30, 2003 8:35 am

My car just recently started idling horrible. I removed the AIV, valve cleaned the throttle body, check the MAS sensor connections, put new plug wires on, new spark plugs, checked connections on injecctors and still it will drop to about 400 or so and bounce back up to about 1000. Then last night when driving it, it would start missing while cruising, and it is missing bad and surging in like 2nd and 3rd. Also while watching my air fuel ratio gauge ti is bouncing from lean to rich real bad, it just goes back and forth as opposed to when cruising at a steady speed staying in the ideal area instead of from lean to rich. and when stopped it sits on rich. I just replaceed the O2 sensor a week ago so I don't think it is the o2 that is messed up. Does anyone have any suggestions on what is wrong and how I could possibly fix this problem. All replies are greatly appreciated. Thanks

Post by **lifeofshadoze** » Sun Mar 30, 2003 8:35 am

did this problem begin after you installed the new 02 sensor?

Website · Post by **93Twiztid240** » Sun Mar 30, 2003 8:35 am

no it was occuring before I replaced it.

Post by **lifeofshadoze** » Sun Mar 30, 2003 8:35 am

my friend has the EXACT same thing as you, same year, and problem with his a/f gauge even. Were looking into it as well, tho his idle isnt as drastic as yours, its still running very rich to lean and sticks somewhat awful.

Post by **DAEDALUS** » Sun Mar 30, 2003 8:35 am

Did you check the MAF connection?

Website · Post by **93Twiztid240** » Sun Mar 30, 2003 8:35 am

I checked the MAF connections and it all seems to be in good working order. No corrosion or anything on the connections and it is making a good connect. I have upgraded my fuel pump with a walbro 255 and I am thinking when that was installed maybe some dirt fell down in the tank and maybe my fuel filter needs to be changed... b/c my fuel pump sounds different now then when it was installed. So I am going to check that tonight

Post by **Rownan** » Sun Mar 30, 2003 8:35 am

93Twiztid240 wrote:I checked the MAF connections and it all seems to be in good working order. No corrosion or anything on the connections and it is making a good connect. I have upgraded my fuel pump with a walbro 255 and I am thinking when that was installed maybe some dirt fell down in the tank and maybe my fuel filter needs to be changed... b/c my fuel pump sounds different now then when it was installed. So I am going to check that tonight

How does the pump sound?

Website · Post by **93Twiztid240** » Sun Mar 30, 2003 8:35 am

The only smoke I am getting is from under the car I believe from where I put on my header and didn't have a gasket between the cat and the header. The pump when I installed it you could hear it whining in the back and now it seems like when you put it in reverse or 1st and go to take off it starts whining louder like it is struggling to pump... And when I am cruising the second I let my foot off the gas the a/f ratio gauge goes right to lean and no lights at all are on... and ,y throttle response is horrible now. Also today when I started it up it keep acting like it wanted to stall really bad. I need to change the fuel filter I just haven't had time... does anyone else think this might be the prob. since I have upgraded my pump? Should I use the 300 TT filter?

Website · Post by **93Twiztid240** » Sun Mar 30, 2003 8:35 am

Update- I changed the fuel filter I went with the 300 TT. This didn't fix my problem.... so I filled up threw some fuel injector cleaner in and I am going to see if that works... and does anyone have any other suggestions?

Post by **Open4Cycle** » Sun Mar 30, 2003 8:35 am

Trouble Codes?

Post by **Nismo_Freak** » Sun Mar 30, 2003 8:35 am

It sounds to me like an 02 sensor problem if it's occuring at partial throttle. Try cleaning your MAF and plug up any holes in the intake and exhaust. Pull the 02 sensor and make sure it is still ok. Even if its new there is always the possibility that it has broken. You can try spraying some carb cleaner into the 02 sensor to clean it, make sure the can says it's ok for 02 sensors first.

Here's some things to check for:

1. 02 Sensor Function2. Holes in intake and exhaust, any place air can get in. 3. AIV valve is still working4. Crankcase Ventilation System is still working5. Timing is ok. 6. ECU Error Codes7. Adjust the idle screw

Post by **DAEDALUS** » Sun Mar 30, 2003 8:35 am

Sorry, didn't read your first post well enough about the MAS being OK. I'll go with Nismo_Freak on #2, especially if not all seals and gaskets were replaced the last time any work was done. Get a can of spray carb cleaner and spray a mist around all intake connections. Watch for the mist to get sucked into any cracks, and listen for an increase in idle. If you can pull the ECU, you can take a small wire, solder it to a multimeter, and check various pins' voltages while the car is running. But be VERY careful not to short any two pins together, you could fry your ECU. The FSM should tell you which pin goes to which sensor.

Website · Post by **93Twiztid240** » Sun Mar 30, 2003 8:35 am

Here is another possible solution...... I have my intake and header installed currently and I am running a stock exhaust (muffler) I know the 240s come with a dual outlet muffler stock but when I got my car it didn't have a muffler and the first day I had it I got a ticket for improper equipment so I went to the exhaust shop and they put on a single outlet very restrictive muffler and that is still on there, do you think with the increased airflow from the intake and header it is creating some back pressure that is foulingi the O2? is this a possibility?

Post by **Nismo_Freak** » Sun Mar 30, 2003 8:35 am

Doubt it, the motor would still push out the exhaust gas. It sounds to me like you have a leak somewhere.

Website · Post by **93Twiztid240** » Sun Mar 30, 2003 8:35 am

no leaks.... but I think I found the problem..... I installed a walbro 255l fuel pump and the thing is whining really really bad now..... so I think my fuel pump is shot. I am going to put the stock one back in tomorrow and see if that will do the trick... if not then its back to the drawing board....

Post by **Nielsen** » Sun Mar 30, 2003 8:35 am

actually I am having the similar/same problem your car has now.

but it now is just intermittent, one day it can run perfectly like in the before, but the other day, it would act like an old man...

I have changed an distributor bcs the nissan dealer diagnosed my car and the computer read " camshaft position sensor error ", which located in the distributor, after changing parts from a same 93 240sx, nothing improved, but one friend tried to adjust the timing screw (mounting the distributor), it improves a lot for several days. and overall experience is better, but still sometimes it stalls when very low speed and sometimes you can feel the turbulence in speed when in 80 or 100KM/h

maybe trying to fasten/unfasten the screw can do some help? you can give a try.

but I am totally lost.

Post by **DAEDALUS** » Sun Mar 30, 2003 8:35 am

It's probably worth it to get a $30 fuel gauge to save on the labor of replacing the pump (possibly twice), unless you're ceertain that's the problem. It should go to 100psi. Damn handy device.

Post by **SSS** » Sun Mar 30, 2003 8:35 am

I'm having a similar problem too, idles fine for a minute or 2, then the idle drops to about 450-500 before returning to normal. Throttle response is still as good as before i did the heads/cam if not better, o2 has never been changed. Will check over everything listed, including AIV which i think may have not had a good gasket seal to the plenum.

Website · Post by **93Twiztid240** » Sun Mar 30, 2003 8:35 am

Well I changed the fuel pump it took about 15 minutes since I have an extra holder to drop in that has the stock pump on.... it helped a little. I pulled spark plug wires of and had one arcing.... so I fixed this problem helped a little... and with all problems you fix one you have 5 more... and now my throttle response is horrible... there seems to be a little slack in the throttle cable... is this normal?

Post by **yellow_jacket** » Sun Mar 30, 2003 8:35 am

Yes, the throttle cable should have a little slack in it. As far as lack of performance and a crummy idle. If you have changed everything else(plugs,wires, cap, and rotor) go ahead and change the O2 sensor. If it is not reading correctly it will throw the mixture off.

Post by **steven ramos** » Sun Mar 30, 2003 8:35 am

If the car is still running rich to lean,check the coolant temp sensor which goes to the ecu.If this is not working properly the ecu will dump fuel into the motor.

Post by **Nosser25rs** » Sun Mar 30, 2003 8:35 am

Just a thought, checked the fuel pressure regulator? Sounds like it's running rich, could be your problem.

Post by **240fan** » Sun Mar 30, 2003 8:35 am

are we talking aav or aiv? the aav is known problem with rough idle on older cars, see the faq on rough idle on 240sx.org

Question about Horrible Idle

Question about Horrible Idle

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