[Pitcherman]

Ok so the vehicle I'm dealing with here is a 1998 2.5 RS with the DOHC EJ25D. It's stock except for a KN panel filter and a Koyorad radiator. The car has 168k miles on it and as best I can tell from the records got a new shortblock and head gaskets about 60k miles ago.

The problem I'm having is the tachometer on the dash seems to be off. When warmed up it shows the car to be idling at 1100-1200 rpm. At first I thought maybe the previous owner had tried to mess with the idle to hide so kind of issue. When I plug my scan tool into the car the data from the ECU shows the car to be idling at ~700 rpm. I don't have the AC hooked up right now so I can't check to see if it idles up when engaged. I tend to believe the data on the scan tool as the car doesn't feel or sound like it's idling high and in fact I initially felt it might be idling low as occasionally it would shudder just a little when warming up.

Has anyone run into the tachometer on the 98 getting out of calibration? I read on some posts that 97 clusters may have an adjustable resistor on the back of tach to calibrate them. Does anyone know if that's the case on the 98? I know this car's gauge cluster is a bit of an oddball between the 97 and 99 year models so I figured I'd ask the community before taking the cluster out of the dash.

 

[Pitcherman]

Well judging by the 200+ views and no responses I guess I'll be pulling the gauge cluster. If I find a way to accurately test and adjust the tachometer I'll post it up.

 

[stalkergc]

If we knew definitively we would help. I only messed with a cluster once and it was cable driven and I fucked it up so I haven't taken apart a tach since. The earlier ones seem more finicky than the digital later ones. I remember having one of mine be off by like 500-1000.

 

[Pitcherman]

If we knew definitively we would help. I only messed with a cluster once and it was cable driven and I fucked it up so I haven't taken apart a tach since. The earlier ones seem more finicky than the digital later ones. I remember having one of mine be off by like 500-1000.

Sorry, my comment may have come off wrong. I know that people will help if they knew, that's why I gave it a few days to simmer so that people who may not frequent the forum would have time to see it and respond if they knew. A couple hundred views seems like I may be on my own here is all. I wasn't trying to sound like an ass.

 

[mike-tracy]

GROM on Facebook can adjust your tach if there's nothing otherwise wrong. He reprograms one of the chips.

If there is a resistor, I'd probably attempt soldering a new matching one in and go from there.

 

[silverton]

If your ECM is displaying the correct RPM and the tach isn't, it's the tach.