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Accelerator flat spot

Tech Talk for Mitsubishi owners.

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Posts: 23
Joined: Tue Mar 25, 2008 3:29 pm
Location: Pomona Qld

Accelerator flat spot

Post by Salty »

Can anyone tell me what cause a flat spot when I slowly push the go pedal on my NH 3 ltr ? It seems to be worst of all before the motor really warms up which causes a non normal auto gear change.
All help appreciated.
Regards Salty.
Posts: 1107
Joined: Wed Jul 20, 2005 6:44 pm
Location: Melbourne

Post by hudson44 »

Dead set. The last few times there has been a problem with my car, i've fixed it, and when i jump on outers of a night time there has been a thread about it. It's bloody spinning me out!

Mine was doing a similar thing (mine is manual tho) where it was almost surging, bogging down mid rev range and was worse when cold and after idling for a while. I advanced the timing a little which helped but it would ping under high load. I thought i would check the TPS (throttle pos. sensor) as the airflow meter is a karmen vortex type which never normally give problems.

Now using a multimeter, the voltage reading between pin 3 and ground should be about 0.8v at idle and 5 volt at WOT. (presuming the voltage reg in the ECU is working and sending out a 5 volt reference). Tested mine today and it was 0.8 at idle but only 3.9v at WOT. So i "advanced" the TPS until it was about 4.7v @ WOT and 1.3v at idle. Bingo!!!! problem solved. I also added a few degrees of timing again and no pinging.

Now to me this would indicate that the potentiometer in the TPS was slightly out and not giving the ECU the full 1-5v adjustment that it needs. The luxury i have tho is mine is manual and it doesn't need to be spot on for the Auto shifting. (and i'm a tight arse)

I would start by checking the voltages at the TPS and adjusting the switch with a bit of trial and error. If the engine revs smoother but the auto shift is still dodgy then it may need replacing. Its somewhere to start anyway. Good luck
Posts: 176
Joined: Tue Dec 11, 2007 10:10 pm
Location: Perth

Post by scooby_74 »

check that your air pipe from air flow meter to throttle body is in good nic aswell mine had a huge flat spot and the air pipe had a tear allowing air to bypass the air flow meter.
93 NJ,5 speed,2" body lift,32" muddies

There's nuttn like momentum
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