idle jumps between 1200-2000 rpm when rolling with the clutch in. any ideas?

75

Asked by Mar 21, 2012 at 10:03 PM about the 1997 Mitsubishi 3000GT 2 Dr SL Hatchback

Question type: Maintenance & Repair

i have no idea what could be causing it, and it has a high idle when it wants to (yes, when IT wants to). sometimes it will idle at
1300rpm, and other days it will idle dead at 2000 rpm. but then when its in a good mood it will idle at 900 rpm.

now to the real problem, it will jump when its rolling, at 1300rpm-2000rpm. ive adjusted the idle control, but again, it doesnt do
much. help?

8 Answers

135

I had a similar problem recently and had to replace the IAC valve. It's the "Idle Air Control Valve" it is under the throttle body slightly to the left and has a plug attached to it. I was having a surging problem too and mine was corroded and not working keeping my idle high. I have replaced mine but still need to reset the TPS, SAS and dashspot.

3 out of 3 people think this is helpful.
75

ive been told it could be the ecu, is that possible?

35

Could be air flow or maf sensors. I had a similar problem on my Scooby STi V5 and replaced both sensors, it worked a treat.

135

Yes, it is possible so one of the things you need to do is pull the ECU. It is inside the car below the radio and it's pretty easy to get to and remove. Pull both side covers of the console. The plugs are on the driver side with a screw to hold it in place and then there is a screw on the passenger side which also holds it in place. Pull the ECU, open it and look for leakage from the caps or capacitors or blown capacitors. There are 4 of them, they look like little round cans with an X on the top. If blown, the tops will be dome shaped if they are good the tops are flat, then look for leaks or signs of leaks at the bottoms of those caps. If you see leaks then you must replace the caps if everything is dry and not blown, replace the ECU cause it's still more likely that the PTU is bad. Like I said, the PTU can test good, then after warming up it can stop firing 3-6.

5 out of 5 people think this is helpful.
135

OOps, sorry, we were talking about the IAC valve. You can still test the ECU like I said but more than likely it's the IAC. Remember that even if you replace the IAC you still need to reset the BIS, Dashspot, and TPS.

2 out of 2 people think this is helpful.
75

it ended up being just the iac sensor. replaced it for 50$ and now its idling perfectly at 900rpm

2 out of 2 people think this is helpful.
75

old one is on the left, you can sorta see where it fried. got a new one off of ebay for about $50 with shipping

1 out of 1 people think this is helpful.

Hey man is it same place on 95 3000gt sl ? Standard ?

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