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Discussion Starter #1
Its a B21A1 90 SI. It has recently started to endlessly stumble at idle, and it seems like it even might be stumbling under acceleration also. For a problem like this where should I begin? It overheated recently because of a bad thermostat, i replaced it, flushed out the cooling system, checked the oil and coolant for oil and coolant, its not smoking, and it warms up ok. So I'm kinda thinking it might be something on the Throttle body, or maybe the dizzy timing. Any ideas?
 

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Any stored trouble codes?

There are other ways for a head gasket to fail besides seeing oil and coolant mixed. Do a compression test and see how your cylinder pressures look. Be sure to pull all four spark plugs when testing compression, and hold the throttle wide open while cranking. I'd bet that your overheating has something to do with this if it idled fine before it overheated. It's very common for the head gasket to become damaged when you overheat these engines.

Why do you think it's the throttle body? Are you psychic, or do you have a reason to suspect that's where the problem is?
 

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Discussion Starter #3 (Edited)
Any stored trouble codes?

There are other ways for a head gasket to fail besides seeing oil and coolant mixed. Do a compression test and see how your cylinder pressures look. Be sure to pull all four spark plugs when testing compression, and hold the throttle wide open while cranking. I'd bet that your overheating has something to do with this if it idled fine before it overheated. It's very common for the head gasket to become damaged when you overheat these engines.

Why do you think it's the throttle body? Are you psychic, or do you have a reason to suspect that's where the problem is?
Idle problems tend to have something to do with the IAC, or the Fast Idle Valve from what I've read. Just wondering if they could have something to do with it. The cooling system had some debris in it and I'm wondering if that could've cause something to get lodged somewhere. I've replaced all of the coolant lines, and flushed the system thoroughly, it should be free of any particulates now.

No stored trouble codes. I really hope its not the head gasket... I just had a new timing belt put on. x_x
 

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So how do I isolate an issue like this? The only code being tn is code 41 for the o2 sensor heater, and its been like that for a while.
 

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So how do I isolate an issue like this? The only code being tn is code 41 for the o2 sensor heater, and its been like that for a while.
If you're going to ask for help, at least do us the favor of taking it or telling us to go to hell. But ignoring it and continuing to ask for help isn't going to make us want to help you. Have you checked the compression as was suggested? You overheated your engine, and now it's not running right. Do you think the two are unrelated?

You have a bad o2 sensor if you're seeing a code 41. That means the heater in the o2 sensor is bad or you have a bad wire going to the sensor. Inspect the wiring and replace the o2 sensor if the wiring is sound. It's not likely your code 41 is causing your issue, but the first thing you should do when you are having car problems is to fix what's causing the trouble codes and move from there.
 

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If you're going to ask for help, at least do us the favor of taking it or telling us to go to hell. But ignoring it and continuing to ask for help isn't going to make us want to help you. Have you checked the compression as was suggested? You overheated your engine, and now it's not running right. Do you think the two are unrelated?

You have a bad o2 sensor if you're seeing a code 41. That means the heater in the o2 sensor is bad or you have a bad wire going to the sensor. Inspect the wiring and replace the o2 sensor if the wiring is sound. It's not likely your code 41 is causing your issue, but the first thing you should do when you are having car problems is to fix what's causing the trouble codes and move from there.
Compression test on the cylinders all got about 167 with about a 4 point varriance between cylinders. Sorry I didnt mean to seem like i as ignoring your advice.
 
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