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Need Help! 1998 Civic Idle Issues

So, I was messing with my car because it had idle issues. It idled fine in the night and idles low in the day. So I changed IACV and tps sensor. Check tps to be calibrated at .50 TB closed and 4.57 open. That’s what my car gave me. I also moved the idle screw to be opened only 2 complete turns. That’s all I did. Went for a test drive and ran the same low idle about 400 rpms to where the engine shakes, in the day. Funny thing was I turned on the ac or hot air at full blast during the day and then car would idle at 700 -800 which is normal rpms/Idle to where it should be. What can be the problem?

I’ll appreciate any advice I’m really tired of my car not running well.

I was also told by a friend it could be the oil being too thin. I have 5w-30 oil and said it should have 10w-40 or 30

Don’t ever let that “friend” work on your car.

5W30 was recommended when your car was new. Honda has retroactively changed their recommendation to 5W20 for your car. Motor oil viscosity will not change idle RPM.

Your friend has no idea what he is talking about .

If You changed the IAC valve did you use a fresh gasket and inspect that the port where it attaches is not blocked with carbon.

I think that the lack of replies to this post, is that everyone is stumped with the Issue that it appears to fun fine at night. This should make no difference to the idle.

You have heard of “Daily Driver”. maybe this is a “Nightly Driver”.:rofl:


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Maybe your car has some Transylvania DNA and just suffers when exposed to sunlight.

:vampire: I bet the car is getting ready for Halloween :vampire: