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same speed different rpm
Hey all, wondering if you can give me an explanation for this. I've noticed for a while now that my car RPM changes by about 300rpm. I have picture proof but can't upload them from work at the moment. Anyway, I took the pics in 4th gear at 60km/h and in one pic the RPM reads 3000, the other 2700. I know about the fast idle if my engine is cold, and indeed it'll idle as high as 2-2500 rpm when cold and drops to around 1300rpm when warm, but then when it's at the "lower rpm", it idles sometimes below 1000rpm. There isn't really any problem with the idling tho, I've only noticed at the really really low idle it sometimes has a slight drop in it like it may stall but never does.
The technical specs are that I'm driving a 92 lude but the previous owner swapped the engine out with a 96 or 97 JDM H22A with the tranny and clutch so it's a good, fast engine. I'm wondering if the problem is simply in the tachometer but I'm fairly sure it's accurate based on the sound.
Also, only one time I noticed the tach suddenly drop 300 rpm while idling and then it was in that "lower rpm" behaviour. I can't really understand why or how it would change my gear ratios but when it's higher as it's been pretty consistently all winter, I drive around in 5th to keep the rpm at 3000 going 60km/h. Pretty wierd stuff. I don't know if this is related but I also occasionally notice a "hiccup" when accelerating hard through 2500-2800 rpm - like a quick hesitation or something but I've read about it before like it's a common problem.
Any help or suggestions is much appreciated!
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Linear Mode
