another poor idle post

[funky technician]

Ok, I can't quite understand whats happening now, my 93 festi auto is still idleing like poo when warm, but it seems fine cold. Its not untill it warms up it seems to hunt for a stable idle, and if i'm slowing down to a stop, if stop too abruptly sometimes when its warm, it bogs so much it stalls. When its hunting for idle too, it seems to find a good idle, then go low, then back to normal, then low and so on. It also seems to miss sometimes, but these symptoms are only present with a warm engine. I should add that I recently put a b6 head and exhaust on, but kept the b3 intake manifold, and i had this problem with the old b3 head

[nattyphysicist]

Hey, shouts out to the east coast.

When the car is warming up, a solenoid valve is open which bypasses the throttle plate. That makes your car idle high and steady to warm up. Once it's warm, that closes and there's another bypass valve, the idle speed control valve, that controls the idle.

The ISC is controlled by the ECU, but I'm not exactly sure how. It may use a lookup table that gets slowly refined as you drive the car. In that case, the problem may go away after awhile provided that you don't disconnect your battery. I would think that modifications to your exhaust or intake would cause the stock settings not to work well, but I'm not positive.

If you haven't disconnected your battery lately, then I would suspect your ISC to be malfunctioning. You can try to clean it, or replace it.

Let me know how it turns out. I also have a crappy idle and I tried cleaning the ISC to no avail. The problem has gotten better though. I'm not stalling out and the idle is a bit more stable, but still oscillates a bit before settling out.

[ericsmith32]

A different animal but on the Aspire I used to have I had the same problem. The cause wasn't the idle control valve but a impropely set idle. There's a screw that holds open the plate and that's what I had to adjust. The only thing I could figure was that the computer was trying to adjust for a high idle because it would float on the idle as well.

[funky technician]

well, I went out and looked at the intake maniforld, I dont see any other corntol sensors other then the TPS and tucked in behind that is a small rubber plug with an adjustment screw in it, what is that? I also noticed that other then the EGR and the TPS, there are no other sensors on the intake manifold, the had cleaned the TPS before, and since its only a few contacts inside it, I doubt thats the problem for they all seem to be clean and making contact, this problem seems to be getting worse too, it stalls more often now when I slow to a stop, and also if I give the throttle a snap, it doesn't recover from it well and sometimes it stalls.

[Tom]

Change the fuel filter again and also ad a yellow bottle of heat.

[funky technician]

been done, but thanks

[nattyphysicist]

well, I went out and looked at the intake maniforld, I dont see any other corntol sensors other then the TPS and tucked in behind that is a small rubber plug with an adjustment screw in it, what is that? I also noticed that other then the EGR and the TPS, there are no other sensors on the intake manifold, the had cleaned the TPS before, and since its only a few contacts inside it, I doubt thats the problem for they all seem to be clean and making contact, this problem seems to be getting worse too, it stalls more often now when I slow to a stop, and also if I give the throttle a snap, it doesn't recover from it well and sometimes it stalls.

The ISC is not a sensor. It will have a hose or 2 connected to it. I've only inspected this problem on my BP, so I can't really speak for the B3. But when the throttle plate is closed, something has to keep the car going, ie provide some air. The rubber plug sounds like the cap to the idle adjustment screw.

[ericsmith32]

Don't mess with the screw under the cap. I believe it's the air/fuel ratio. The egr on my Aspire I had to clean it was plugged completely. I guess your festiva is a cali car.. I didn't think any other festiva's had egr.

[nattyphysicist]

wait, is this fuel injected or carbed? It's a 93, so has to be EFI no? If it's EFI, then why would it have a mixture control?

[funky technician]

its fuel injected, and I dont' know what that lil screw is under that rubber cap, and no it isn't a cali car, almost all cars have an egr valve, it reduces combustion temperatures and reduces the risk of valve burn, but I was just wondering if it was stuck open, if that would cause these symptoms
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