As in title, if I rev my car the revs will drop as normal to around 2000rpm or so and then slow down and sit at around 1300-1500rpm for a while, up to 10 seconds and beyond sometimes, before eventually dropping down to idle speed.

I've cleaned MAF and throttle body.
Also swapped in different ISC and TPS (second hand ones, but no change).

The other problem I get which may be related? is the car is very jerky when 'just' on and off throttle.

Any had this?

have you recently disconnected the battery? My car used to do it after i disconnected the battery while cleaning engine bay. It eventually went away, its just the ecu just takes a bit to relearn your driving

No it's not an ECU reset problem, and has been going on a couple months.

Have you checked the TPS is properly adjusted

No, I just lined the replacement up with original mark.

How is adjustment checked Mal?

You can have the TPS adjusted using the MUTII by a Mitsu dealership or do it yourself with a multimeter.

Basically:
- Start by putting a feeler guage between the back of the throttle levers. I beleive its 1mm for a throttle body with cruise (10 cent coin) or 1.4mm for a throttle body without cruise.
- Take off tps plug to expose the tps pins.
- Put the mutlitmeter to test Continuity. Basically the --|>- setting.
- Hook up the two prongs to Pin 1 and Pin 2 on the tps connector (6cyl). Pin 1 is the first pin from the bottom of the plug. I used some alligator clips and wire to keep a steady connection.
- Undo the screws enough to make the tps turn. Do not remove the tps.
- Turn the sensor fully anti-clockwise.
- Now with the mutlimeter on the continuity function turn the tps clockwise until you reach to the point before you have continuity - i.e. when the reading is not 1. You want to tighten the tps to the point just before there is continuity as this is when the ISC is off.
And that's it. Tighten down the tps and it should be right to go. You can also check Pin 1 & 3 on the tps plug/harness with the ignition set to on (engine off) and check you're getting a reading of 400-1000mW.

thanks

Forget the feeler guages for the manual, simply use the multimeter and adjust until the idle switch is active with the throttle plate closed. WHile the above method is the correct one, experience has found for me that it is not close enough to closed throttle and you will find the car still jerky

Old TPS switches can be cranky and the car can still be jerky when it is adjusted correctly as per above.
I've found you can tweak the TPS by tiny adjustments to get the car to stop jerking and change smoothly, trial and error though. My car used to change down to first when slowing down with throttle off with a clunk, should stay in second until you apply some throttle on takeoff. Slight tweakage fixed it.

Forget the feeler guages for the manual, simply use the multimeter and adjust until the idle switch is active with the throttle plate closed. WHile the above method is the correct one, experience has found for me that it is not close enough to closed throttle and you will find the car still jerky

How would you know when the Idle switch is active?

How would you know when the Idle switch is active?

Please re read my post, it is all there in the first sentance, adjust so switch is operative with throttle closed, as soon as you start to open the plate you should then have the idle switch off

Thanks all.
Better go buy myself a multimeter then.

Hi Brett H,

Was your issue resolved I am having the same problem and have tried pretty much every thing. Any thing I can try?

I had the same issue after i replaced my clutch (battery was disconnected for a few days.) Some days it was worse than others so I didn't look into it at the time. A few months later I decided to clean the TB, intake and ISC while I replaced the plugs and rocker gaskets. It still wasn't right, so I D/C the battery again, left it for a few mins, reconnect, start and allow idle for several minutes and it's been perfect since.

Hi Brett H,

Was your issue resolved I am having the same problem and have tried pretty much every thing. Any thing I can try?


No, it's better but I still haven't resolved it fully, even after adjusting the TPS with a multimeter as described above.

The jerkiness is a bit better but i still get the hanging revs (the revs never drop down from 2000rpm to idle as quickly as they should) and high idle (however it is still inconsisitent and the idle will sometimes drop down and settle on 1000rpm and other times will just sit up at 1300rpm).

I took it to another mechanic for another opinion and he reckons everything is fine and my cams are causing the problem, saying that the extra duration fools the 02 sensors.
However I had this same problem before I installed the cams as well!!

I'm just putting up with it at the moment (haven't driven it for 5 weeks anyway), but once i can get some cash saved up I'll buy a brand new TPS and ISC. If that doesn't help I'll look at swapping the throttle body (maybe it is causing a problem)?

Do you have cruise control?
If yes, disconnect the hose that runs from the cruise control motor and see if this makes a difference.

No cruise.

vacuum leak?

"Vacuum Leak?" If you have had your intake manifold off lately, it is possible that you have a leak in the gasket or in the vacuum hoses Check these.

that was an possible cause I considered so it was all taken off and re-done.

Still no change.