93 240 runs but wont idle right please help!
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maniacman9558
- Posts: 71
- Joined: Sat Aug 01, 2009 2:50 pm
- Car: 93 240sx n/a KADE (for now! =P)
05 ninja zx10r - Location: lancaster, PA
93 240 runs but wont idle right please help!
alright so i just rebuild my KA and got it back in and i got it running again but its acting weird. when you first start it up it will idle fine but after it runs for a little it starts to idle weird and it sputters when you give it throttle. i just replaced fuel pump and one of my injectors was bad so replaced it and still nothing.and i know my MAF is bad so have that desconected..i know that makes it so it wont rev past like 2500 would that also be why it idles weird after like 5mins??
Re: 93 240 runs but wont idle right please help! (maniacman9558)
I cant remember offhand, so this is really just a scientific wild a** guess, but it seems like sound advice to me so maybe I'm right.
When the car is warming up it puts the computer in whats called an open loop system. The oxygen sensor data is discarded as its readings wont be accurate until the system has warmed up. Other extraneous info is also ignored, probably including the mass air flow sensor. However when the vehicle warms up and the ECU starts collecting info from the sensors, that disconnected MAFS is not sending any info so the system goes haywire.
I'm willing to bet that your MAFS is the issue here as well. I'm thinking if you replace it everything will go back to normal.
When the car is warming up it puts the computer in whats called an open loop system. The oxygen sensor data is discarded as its readings wont be accurate until the system has warmed up. Other extraneous info is also ignored, probably including the mass air flow sensor. However when the vehicle warms up and the ECU starts collecting info from the sensors, that disconnected MAFS is not sending any info so the system goes haywire.
I'm willing to bet that your MAFS is the issue here as well. I'm thinking if you replace it everything will go back to normal.
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maniacman9558
- Posts: 71
- Joined: Sat Aug 01, 2009 2:50 pm
- Car: 93 240sx n/a KADE (for now! =P)
05 ninja zx10r - Location: lancaster, PA
Re: 93 240 runs but wont idle right please help! (xekushnr)
hmm well i think my maf is fine but i will have to check it. i got 4 diff mafs and they all (doing the disconect method) acted as if they were bad but then it went fine after it was warmed up but i will have to use my multi meter to actually check it the more accurate way.
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Drifterxxl
- Posts: 140
- Joined: Sun May 21, 2006 1:26 pm
- Car: 95 S14
- Contact:
Re: 93 240 runs but wont idle right please help! (xekushnr)
I believe part of your problem is your maf or a cause of it. When you start your car the PCM aka ECU relies on the ECT sensor until vehicle goes into closed loop.
If you are positive your maf is good which with vehicle running in idle you should see 1.2v up to 1.6v and that should increase as throttle plate is opened you should see voltage increase to 4.5v to 5v.
One other condition that is a possibility is a false air condition or non metered air, vacuum leak after the maf sensor. As for Not revving past 2500rpm (limp mode) yes maf unplugged will do that and also cause the vehicle to stall PCM reads how much is passing through to determine fuel trim values. With out the PCM ( powertrain control module) getting a signal from maf will cause a weird idle.
If you are positive your maf is good which with vehicle running in idle you should see 1.2v up to 1.6v and that should increase as throttle plate is opened you should see voltage increase to 4.5v to 5v.
One other condition that is a possibility is a false air condition or non metered air, vacuum leak after the maf sensor. As for Not revving past 2500rpm (limp mode) yes maf unplugged will do that and also cause the vehicle to stall PCM reads how much is passing through to determine fuel trim values. With out the PCM ( powertrain control module) getting a signal from maf will cause a weird idle.