So I've been trying to trace what I thought was an idle issue. After testing all sensors in the engine bay and everything testing good I finally got smart and took it to a tuner. First thing I had him do was look at the rpms with his laptop and just as I thought....finally... my rpms on my tach are reading too low at idle rpms...ie 800 rpms.

When I pulled the iacv with him looking at his laptop I asked him what it read...he said 800. I thought there was no way since my tach is showing 600. So I moved the idle screw down and it took a turn or so(surprisingly) and it finally started going down. I set it to 600, turned the car off, reconnected the iacv, and like magic it's actually at 800 on his laptop. However, the gauge reads down by 0. And I literally mean 0. It's about 200 or so since the gap between 500 and 0 is so small.

Even with it that low, when I turn accessories on, it actually bumps up(going by the laptop, and on the tachometer, even with it pegging down by 200, i can still see it bump slightly up on the tach). I have never seen this happen on my car. I don't even think it did it with the original motor so I don't know how long this has been bad. I think my idle was off on the original motor too. The thing about it is that even when it idled low during it's down cycle when I had the idle setting too high it never vibrated like it was low on rpms so I kinda shoulda figured to check actual rpms. I kinda always thought that my car was running fine. I have a timing gun but not one with rpm capability.

So, if you are having what appears to be idling problems but the car doesn't shake when the rpms are low, it could be your tachometer is off. Now I just need to grab another from the junkyard though it is supposedly possible to calibrate mine. I know the h22a uses the same ignitor which is where the tach gets its signal from so I don't think this is related to the engine swap.

This is great because after a tank of gas I am now getting more mpg's since the idle rpms are lower and it doesn't lope up with the headlights on anymore. If you think tach's rarely go bad, they do, and they do it without completely dying or bouncing all over the place.

 

So after about 3 days of my rpms being around 0, I start my car today and without having gone anywhere near my engine bay since that time, my rpms are completely and totally normal, for the first time since I got it a couple years ago or so. They stay right around 750-850 the entire time when warmed up, hanging out around 750 with no loads and going up with each additional load to around 850.

I feel like this car has taken on the spirit of "Christine", for those of you that have seen that movie.

It just keeps getting more interesting. Atleast everything is normal now, if you call it that.

 

that makes 2 christine's lol my tach will bounce sometimes on cold mornings. i havnt really looked into why it does bounce or even drop to "0" while crusing at say 3500rpm

 

swap your tach for a digital one... Im doing this now and eventually digital speedo too

 

i have seen too many engines get blown do to digital tach's and not reading correctly in higher rpms....if i where to replace the tach it would be a small 2 inch autometer or even a huge 6 inch tach with a shift light and recall haha

 

Ive seen the opposite. Digital internal, analog dial is what ive usually seen. My dash is currently being modded to digital speedo as well

 

ahh thought you where talking about say one that reads like a digital alarm clock....sorry man