bigsquat

can anyone help me with trouble shooting my ISC motor!!!

ive been having problems with my 1997 geo metro it would stall under hard deceleration and then it would start right back up . while finding many problems that i corrected like the egr replaced, short of a wire to ground in the harness, new cmp, changed coils, igniter, noise supressor, injector resistor, tps, map,ckp,isc, pcm ,vacum leak in the brakebooster line and loose hot and ground at the battery and loose ground at the tranny to battery . i added more ground jumpers all over the motor to firewall and battery just for kicks. what happens now is the if i remove one of the battery leads for a while and then put it back ,the car will start fine and idle great . once it gets warm it the isc motor starts raising and lowering the throttle and then shortly after that it will die. and not start. its getting gas ,20lbs pressure but no spark, the tps is set at 1volt dc with the thottle set up with a .14 feeler gauge. the ckp puts out .50vac and the cmp puts out .37 vac. vacuum reads 19. 14 before i changed the egr. the one thing that im having trouble testing is the idle contact in the isc motor. it shows a dry n.c. contact which is supposed to open when you give it gas. i put a continuity tester on the leads going to the contact and get no reading in any throttle position. thats why i replaced the isc. well the one from the wreckers did the same thing. so i went back to the wreckers and checked 5 that where there and i couldnt read thru any off them. so either im not properly testing them or there all bad. or the factory decided to save money and leave the contact outI(joke) please help, im loosing my mind .

edit: i changed the statment about the contact to n.c. because there are differnt drawings that show it differnt and i think mines supposed to be normaly closed at idle.

EinST

Welcome to the forum. I can't say I'm familiar with the 1997 Geo Metro (1.3L?) but are you talking about the idle switch at the ISC? If so, test the continuity across terminals 5 (BLK/BLU wire) and 6 (GRY/GRN wire)?

bigsquat

its a 1 liter but the same isc. the earlier models had the idle switch in the tps but i think around 95 or so the moved them to the isc. i try to read thru those points but i cant get a reading. thats why i thought they were burnt out. but after checking 6 of them now and cant read any of them , i thought i was missing something. maybe geos use photons instead of electrons! maybe thats why all the geos i tested were in the wrecking yard, they had bad contacts and the owners gave up trying to fix them. theres no codes on the ecu. the drawing i posted shows the contacts but disregard the notes about the testing of the motor. i just use a 9 volt battery for that

EinST

Hmm, that's bizarre, unless you had the electrical connector in place and were just backprobing pins 5 and 6 through back of the connector in which case you aren't isolating the switch.

bigsquat

no it was discoed, i started unwraping the hole harness and checking for more problems but i really need to get that swicth to work, i cant aford a new one there out of site. and they recomend buying the whole throttle body as a set!. i think ill find another contact that i cant mount externally to the throttle and wire it in to replace the ghost one. if anyone has a metro ,can you see if you can read between 5 and 6?

bigsquat

i got the wiring harness back together and hooked in some wire leads to term #5 and #6 of the isc. i connected the ends together to simulate a closed contact. it started right up but ran like crap! i thought omg wtf did i screw up in the harness! a check engine light came on #300, engine missfire(that narows it down lol) any way after almost commiting suicide i found i had knocked off the vacuum lead to the map sensor. whew!
i plugged it back in and it fired up and it idled great. i ran it at idle a while untill it warmed up and the isc motor stayed steady . now i wanted to simulate high speed so when i would open the throttle i would open the ends of the wires. it worked great and no stalling. so its got to be those contacts. well i hope it is . now to figure out why all the ones ive checked i cant get a reading.

eshad

Note about this Idle Speed Control (ISC) on a 1997 Geo Metro 1.0L. It is a glorified AC idle solenoid. If it jams open, or surges, just unbolt it and reposition it out of reach of the throttle. Leave its electrical harness connected but remount it where it cannot reach the throttle lever. Then set up the idle manually with the idle set screw. Give it enough rpm to compensate for AC cycling. My AC has quit anyway.

bigsquat

i went to the wreckers and pulled a whole throttle body off with all the sensors attached and it runs good now. the isc motor doesnt change the idle when a load is put on it but at least it doesnt die anymore. i got 55mpg out of it and i hate to mess with it anymore. when i have to get it smogged i might have problems passing the idle test if the radiator fan comes on and the idle drops out of testing specs, i have it set a little high right now and it drops to low when the fan kicks on. thanks for the feedback.

bigsquat

im thinking that the problem was a shorting or malfunctioning injector. since when replacing the throttle body with its injector, tps,isc, heater, all at once its hard to pin down what part fixed it. i do show a code now for a bad cat, but it shouldnt be related