I'm in the market for a new car and found a 1999 honda civic dx with a ls swap from a 98 integra.

While the car is running, it idles extremely weird. Sometimes it will idle fine for a few seconds and then it idles really bad, it kind of sputters and comes very close to stalling but it doesn't actually stall. It doesn't sound anything like an IACV issue. Would it be a vaccum or something wrong with the engine or what?

The owner said it could be some temperature sensor that b series have on the manifold but d series have on the intake, he put some janky "block off plate" on the manifold to block where the sensor would be, could this be it?


The car drives fine when actually driving, doesn't act up at all.