Questionidle-surging:I think I've narrowed it down to faulty ISC motor, but here's what's been done thus far-new battery;new vac lines/hoses;new thermostat;replaced air intake man. gasket;new coolant temp sensor;cleaned and check EGr valve;thoroughly cleaned throttle-body;replaced ISC o-ring, cleaned pintle valve/seat;made a pin-spanner tool to remove fast idle air valve cap/seat and cleaned this; new throttle pos. sensor[the orig checked out of range at 750-6.5k ohms....Haynes Manual called for 1100-5.6k as throttle is moved thru range of motion, using terminals 2&4 of plug];Checked power to ISC motor at plug, getting bat voltage on terms 2&5, as per Haynes; checked ISC motor resistance out of car[terms 1&2 and 5&6]and got w/in range of 28-33 ohms. However, when connecting a 6-volt lantern battery to ISC motor plug[ positive bat leade to jumper across terms 2/5 and neg bat leade to jumper across terms 3/6], I got no movement/vibration in ISC motor. At this point, I decided to plug the ISC motor into its plug on car and turn ign "on"... I then got sporadic vibration in motor, meaning if I tapped on motor, it would vibrate differently, as if something internally was on the verge of not making good connection[similar to bad brushes on a starter motor making intermittent contact w/ armature].At this point,I again did the test on bench w/6 volt battery to appropriate leades, and no vibration again, as per Haynes procedure, so I installed ISC motor on throttle body.Another observation:the molded rubber o-ring in channel at bottom of throttle body seemed quite crushed, and the cover plate looked as perhaps it was not sealing proprly, so I put a small amount of RTV sealant on this to seal better.I also have to run the fast idle air valve cap all the way in[about 6.5 turns in from orig setting]in order for the idle to be 800/1000 rpm.Also, the idle air adj screw has to turned in until it bottoms[ orig about 1 turn out], or the idle is too fast, and surging begins. To add:this all began a month ago when I cleaned the K/N air cleaner, and decided to shoot some carb cleaner around throttle plate to remove carbon, and not knowing that the car would not run with rubber boot off throttle body, I tried starting car to have it running as I sprayed carb cleaner in. I put the boot on, and the surging began at that point. I removed the boot and put more carb cleaner in opening to fiav and the car was ok for several days, then the surging, which I've had ever since. Also, early on as this started, a local repair shop suggested I remove the mass air sensor and clead it w/ CRC mass air sensor cleaner, which I did. They said this cleaner was for this purpose and CRC label said this should be done every time the air element was changed.I've had this car since new[17.5 yrs] and never had a problem like this. The K/N has been it for 50k, so it's not like excessive oil getting on mass air sensor and causing a problem.I almost think that the carb cleaner may have sat near the rubber molded gasket on bottom of TB and caused some deterioration. I also want to note that thru-out all these things I have done, I would disconnect the battery, to be sure any bad codes were erased; also, never a CEL at any time.The car does run better down the hiway[ alot of carbon in plenum and ports removed],but the idle is not right, and I think the ISC motor is not working properly. If it is the problem, I have yet to find a source for one. Any help would be greatly appreciated. This is the best car I have ever owned, and plan to continue to use it for quite a while, but this past month has been a crash course in FI systems. Sincerely, Dick
AnswerDick, when checking the continuity of the motors you should have 4 values: 2&1, 2&3, 5&4, 5&6, since there are 4 windings that you are checking. Your procedure only shows 2 checks. Next your 6V test doesn't sound right. You should be doing 4 of them in a specific order and then in reverse.
bottom line is that these motors are notorious for being bad, and will even take out the computer when they short (and then go open) Verify all the circuits and then do the 6V test. If they don't work, then replace the idle motor. The idle motor can be had, even at the local mitsubishi dealer last time I replaced one. You can also go to www.dsmtuners.com and go to the classifieds. That website has a ton of information and a good source of parts as well. After the new unit is installed, it may take some time for the idle to relearn. Mine always takes about 2 days to be correct. Also, the base idle is best adjusted with a scan tool so that you have 15-20 counts of IAC. Otherwise, the computer will keep adjusting itself in conjunction with your manual adjustments. at 15-20 counts, the IAC can properly control warm and cold idle.
Cleaning the Mass air sensor on yours isn't required like a hot wire film style. The parts guy isn't familiar with the Karman Vortec style sensor. It doesn't have a hot wire that collects the filter oil and gets covered in dirt. A good tip, but not needed on your car!
