wied proble my 94 rx7 is idleling in neutral and the speedo is reading 29mph and my l milage is going up?

any ideas why?

 

anyone?

 

What kind of work have you done recently on the car?

 

It's a problem with the cluster. The speedo is basically acting like a tach, you should be able to rev the car and see the speedo "rev" up as well.

Car in my driveway that I'm working on does the same thing at times.

Dale

 

thats wierd.... my pfc also reads that im doing 29mph...

well i took the upper intake manufold off and then after i put it all back it started to do that...

 

Sounds like a possible ground problem - tach may be grounding thru speedometer. Did you restore all the grounds you may have disturbed after the manifold R&R?

 

the car is secretly telling you she wants to go on a ride

 

There is a ground from the wiring harness at the back near the firewall that normally goes around a rear stud on the upper intake manifold. That's the ground for the instrument cluster. Make sure that's on properly.

Dale

 

did you try unplugging the speedo sensor from the transmission to eliminate a possible problem with the speedo sensor from the transmission?

 

I have the same problem, my car was completely disassembled. New motor etc. I ordered a new speed sensor and will have it tomorrow. I don't think that will fix the problem though. I too think it's a grounding issue. I will post the results after installing the speed sensor.

 

Can say with absolute certainty, not your sender.

Brand new one installed here after a diff ratio change and you'd get the speedo running, tends to go away when warm. Haven't been worried enough to play with it, but there's another earth near the ECU, which could be worth a clean.

 

The V8 swappers have this problem sometimes. The tach wire and speedo wire run very close to each other, and the former causes electromagnetic interference in the latter. Not sure why yours is doing it, perhaps they run closer from the way something was wired in?

 

Changed the sensor, not the problem! As long as they read around 250 ohms they are fine. Still hunting but as said must be a ground.

 

has anyone figured this out yet? Im having the same issues on mine now, I just got the tranny rebuild, and one of the speedo sensor wires got cut accidentally, I soldered it back together and its making a good connection, im running simplified seq with stock ECU, and the only ground not attached is the one on the exhaust after the cat as I am waiting for a few last parts so I can button the car back up.

 

Does anyone have a fix for this? Mines doing the sane thing!

 

mine stopped, but im not sure what I did to fix it. At the time I had to fix some fubar'd wired on the tranny, and ended up checking all the grounds while I was at it. Start there and work your way to the cluster.
Best of luck

 

Had the same thing appear this weekend - hadn't changed a thing on the car. It would sit around 20kmph at 1krpm, and go up as you revved it. Putting the car into gear and very slowly moving forward would drop it immediately to 0kmph.
It seemed to dissapear after a 30min drive, but still appeared the next day when cold, and then it didn't go away when warmed up either.

I tried Dales advice (cleaned the grounds on the UIM, and the ground going from Firewall->UIM), and it seems to have fixed it. Thanks Dale!

Electromagnetic interference seemed like a very plausible explanation, especially given that the speedo reads correctly as soon as the car is moving, plus the fact that cleaning grounds appears to have fixed it.

 

So all you did was clean the grounds on the uim? I did that yesterday and still nothing what should I try now?