Idle Issues

[iamtall77]

I'm still new to 2G's. My idle has been low since I bought the car in March. I have a CEL for Idle Control Emissions or something. Think it's CEL 505. When I run the A/C idle drops to about 200rpms and the oil light tries to come on, meaning there is no oil pressure. Runs great and no other issues besides the dumb CEL for the MPDS. CEL 1405 or something. Is this an issue with one or more of the selinoids on the throttle body? I have no idle surge and no vacuum leaks. The BISS is all the way down. I've had to adjust the idle a little with the idle stop screw on the throttle linkage. I have a 1G TB that should be in good working order. Are the parts for 1G and 2G TB interchangable? I don't want to switch to a 1G TB cause I don't want to port out the manifold or mess with it at all. I'm using it for another project. Where should I start looking?

[Kibo]

First of all, tightening down the BISS lowers the idle. You'll need to back it out to raise the idle. However, you need to tell the ECU you're adjusting the idle so it can "park" the ISC in a nominal position before you adjust the BISS. On a 2G, this is done using a scan tool. I've been told that it can also be done by grounding the appropriate connectors as with a 1G, but I can't find any evidence of that in the service manual. Lastly, all of this should be done with the car at operating temperature and all accessories, A/C, etc. turned off.

You'll probably want to clear the CEL code before doing any of this, as it likely affects the ECU operation. Before clearing it, get the exact code--it's hard to help diagnose a problem when you're not sure of the CEL code (you list two different numbers?).

[Paul]

The manual has specs for the ISC coils.

First back out the BISS. To set it exact you need a scan tool or DSMLink.

Paul

[iamtall77]

The CEL that I have is P0505. It reads as Idle Control System Malfunction. I thought the BISS was supposed to be screwed all the way down? I didn't mess with it since I bought the car, I just plugged the vacuum leak that was coming from it. Maybe the issue is as simple as replacing the O-ring, but I doubt it since there isn't a leak anymore. I thought I did see something about using a connector to adjust the idle. Maybe that was just a 1G or it was something about timing. Can I use my Palm Pilot to make these adjustments. I don't see how, but thought I'd ask. I thought maybe someone could help diagnose where the problem was coming from since it mostly effects the A/C idle. The car idles at about 600-800 when warm. But it dies down to about 200rpms when the A/C is on. Obviously I haven't done this more than once in fear of hurting my engine, but thought it was worth mentioning. Sorry if any of this seems dumb, but I'm still learning about 2G's. I've owned 2 1Gs and have those down pretty good. Let me know if you can think of anything I can try to help narrow down the issue.

[iamtall77]

I still haven't figured this out. And as far as setting the idle, what all is involved as far as the ECU? Can I just set the idle where I want it, and then reset the ECU? What does the Scantool have to do with setting the idle? The main issue I'm having though is that it won't idle correctly when my A/C is on. What part controls this? Maybe I can start there.

[Paul]

I'm not sure (but pretty sure) and perhaps someone else can chime in but if your idle changes like that when you put the A/C on the ISC is bad.

Again, you can check the coils per the manual.

What are your fuel trims?

How do you know you don't have an intake leak?

Back out the BISS a turn and see if that helps.

Paul

[iamtall77]

I know it's not an intake leak cause I did a leak test when I first got the car. The only leak was the BISS screw. I just put some silicone in there to stop it. My fuel trims are fine. I checked them with my Palm the other day. My guess was also the ISC, but I thought I'd ask around first. Is the ISC motor the same on 1G and 2G? If so, I can just swap one over from a TB that I have. I'll check that before I mess with the BISS.

[DSMxTSi]

Is the ISC motor the same on 1G and 2G? If so, I can just swap one over from a TB that I have. I'll check that before I mess with the BISS.

No, they are different. You will need to use a 2g ISC.

[Dane Becher]

No, they are different. You will need to use a 2g ISC.
I think they are simmilar enough that they are interchangable. I know for a fact that a 2g ISC will work on a 1g TB.

Dane

[Dane Becher]

I'm not sure (but pretty sure) and perhaps someone else can chime in but if your idle changes like that when you put the A/C on the ISC is bad.
Paul
Yes, if turning on the A/C drops the idle then your ISC is not functioning properly. With a good working ISC, turning on the A/C should actually increase the idle a bit.

Dane