11-14-2010, 07:05 AM
Join Date: Apr 2010
Total Cats: 0
Suddenly lost idle control- can't figure out why
MS1 V3. '92 Mx5.
I got the MS1 second hand, so I did not build it.
Right- I had fully working idle until about 6 months ago, I came off the motorway and idle shot upto 2.5k rpm. Changing the dc values to the ICV don't give any effect. Unplugging it makes the idle fall back down a bit. Bunging it makes the problem go away- but that's not a solution.
Nothing had been changed in the car so I tried to isolate the problem.
I've replace the ICV- no change.
I've opened up the MS1 and we've got the TIP122 transistor connected up to the Q4 connections, a diode connected to S12 and R39 has been jumped.
Did some continuity checks and the left and middle pins have continuity- is this correct? I suspected transistor failure, but removed it and there was no more continuity.
I assume it's correct for the middle and bottom connectors on Q4 to have continuity?
what checks can I do to check the idle circuit is working correctly?
I've noticed in the MS3 build, the right pin on TIP122 now goes to R43- should i do that? The right pin does go to ground as it is.
Any suggestions welcome. I'm thinking about replacing TIP122, but that's probably not the answer.
Last edited by Paulusuk; 11-14-2010 at 03:52 PM.