ISC going out?

[DiamondStarCar]

Now it's my ISC motor that's going out I believe. When I turn on my a/c the rpm's drop by like 500rpm and the engine almost stalls. I unpluged the dissconected the ISC plug from underneath the TB and turned on the ac...same result. How can I tell if it needs to be replaced or just has a bad ground? Where can you get a new ISC motor and how much does it cost. Thank you so much...my Talon is breaking more and more each day. :thumbdown
NOTE:I went to check the connection with my volt meter...but it too is broken....ahhhhh!!! HELP PLEASE!

 

[CurtTSI]

Go and get a digital volt-ohm meter from Radio Shack. They are really cheap. Measure the resistances between the two center pins of the ISC and the pins on each side of it, a total of 4 measurements. Resistances should be between 28 and 32 ohms. If one of the resistances is very high, you have a bad coil in the ISC. I think a new ISC, from the dealer, is about $250. You can pick them up used for about $50 to $75. I have an extra one that I will sell you for $50 shipped. All coils test good.

 

[DiamondStarCar]

Yeah, Im going to have to buy a new volt/ohm meter because mine is broken...it's a radioshack and was only used a few times. Oh well, im getting another one. But yeah CurtTSI, im interested in your ISC if I find out mine is bad. From the way the rpms drop when I turn on the a/c, does this sound like the problem (without further testing with the volt meter)? I will be able to tell you for sure by the end of the week. Oh, and how high is too high?...like above 32ohms? Thanks for the help though.

 

[Thomas91169]

alsto try resetting the isc.

unplug the isc connector

turn the car to "on" but dont start it

wait 5 seconds

turn the car off and plug in the connector

now see if it works.



i do this to mine about every month. sometimes at a light the car will drop to about 300rpms and hang there till it realizes it and raises it. its about this time if i have the ac on theres 50% less power, so i just resed that isc and itll run fine for another month. works for me, and hell, for 250, i think ill just keep resetting it if thats all it needs.

 

[CurtTSI]

From the way the rpms drop when I turn on the a/c, does this sound like the problem (without further testing with the volt meter)? I will be able to tell you for sure by the end of the week. Oh, and how high is too high?...like above 32ohms? Thanks for the help though.

Yes, a drop in idle speed, when you turn on the A/C, is an indication of a bad ISC. The ISC should adjust the idle to conpensate for it. A bad coil in the ISC will usually test open circuit, a resistance of several thousand ohms. Look to see if one of the 4 resistances measured is far higher than the others.

 

[LaserDad91]

I have been having the same type of problem for about a week or so. I have ck’d the ISC coils, all ck’d OK. I ck’d the TPS, also OK. I also ck’d the Idle set switch??, one on top of T/B and it was OK and set properly. So I did the BLISS adjustment, and no difference, but got it to idle, at least. Then the darn thing started to work OK, so reset the Idle, and then it quits again!!

I did a voltage test, just to see if connector to ISC was getting power, and it is, so I am assuming ECU is outputting OK. I have even ck’d the air and coolant sensors, and they seem OK. Hate intermittent problems!!

Next, going to ck the connector itself, make sure pins are tight. Had a loose set on my cruise control and by using a small pick, I was able to “tighten” the female pins.

I have heard there is an AC temp switch, would that have any effect? Like does the ISC and ECU need to sense anything else other than a drop in idle speed when the AC comes on to correct the condition? I have also read where you can clean the ISC, but then read where solvents will hurt ISC. And yes, I cleaned the TB too………...

Car runs fine other than that, no problems! What about blocking off EGR? I have haead if those start to stick open, that could affect your idle.

This is a 1G, 2.0., N.A. Let me know if you guys have anymore ideas. Thanks!

 

[DiamondStarCar]

Im about to check the ISC again tonight by resetting it (thanks Thomas91169)...the voltmeter still isnt working and Im broke...so I might head to my dad's to use his. Im going to reset it, check the volts, the hopefully come up with some positive results. Oh yeah, another problem (probably a direct result of the bad ISC)...when I start my car now, it jumps up to lik 3k rpms and SLOWLY falls back down to the regular...then surges between 1k rpms and 2k rpms. Yeah my car is in another one of its mood swings. I know all of you have heard this a million times, but my car has it all...at only 95k miles. Thanks again for the help, I will let all know how it goes.

 

[DiamondStarCar]

Sorry to post two in a row here but I busted out my brother's ohm meter and and showed all 33's and 34's...one came up 36ohms, so I tried again and got 34. CurtTSI, all these measurements are over the 32ohms you said was high...but barely...just barely. What do you think? It shows the symptoms with the idle surge, drop of rpms under a/c and ps, etc. Do you think it's a bad ISC?

 

[Quik_GSX]

I think my ISC may be tweaking out on me as well. My idle dips down a little low sometimes and when I turn on the A/C most of the time my idle returns to normal, although not every time.

 

[CurtTSI]

Sorry to post two in a row here but I busted out my brother's ohm meter and and showed all 33's and 34's...one came up 36ohms, so I tried again and got 34. CurtTSI, all these measurements are over the 32ohms you said was high...but barely...just barely. What do you think? It shows the symptoms with the idle surge, drop of rpms under a/c and ps, etc. Do you think it's a bad ISC?

I think that your ISC is probably OK. The 28-33 ohm range is for room temperature conditions. If you tested it, on the car and while warm, you will get somewhat higher readings. The idle surge that you described is also a symptom of a bad ISC. However, it can also be caused by a vacuum leak.