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RPM going crazy after 3k
Posted: January 19th, 2008, 2:19 am
by MidNight
Something weird happened to my MX3 tonight.
I noticed that when i drive more than 2500-3000 rpm, the needle jumped really fast to the red line area. but it still drives the same. It happened to every gear after 2500-3000rpm.
What would be the problem? is it possible that my clutch is going out?
thanks!
Re: RPM going crazy after 3k
Posted: January 19th, 2008, 4:51 am
by mr1in6billion
When you say is drives the same, does the engine sound like it's going to redline?
If you say yes, then it's your clutch.
Re: RPM going crazy after 3k
Posted: January 19th, 2008, 9:25 am
by MidNight
mr1in6billion wrote:When you say is drives the same, does the engine sound like it's going to redline?
If you say yes, then it's your clutch.
no, it sounds the same.
Re: RPM going crazy after 3k
Posted: January 19th, 2008, 5:19 pm
by 94mx3precidia
If your clutch isnt slipping then there really isnt anything else than your spedo sensor. Try getting a new one, i dont think there that expensive.
Re: RPM going crazy after 3k
Posted: January 20th, 2008, 12:04 am
by shameem
Re: RPM going crazy after 3k
Posted: January 20th, 2008, 5:25 am
by umcamara
I don't see what the HEI mod has to do with his issue.

Re: RPM going crazy after 3k
Posted: January 20th, 2008, 3:20 pm
by shameem
umcamara wrote:
I don't see what the HEI mod has to do with his issue.

The RPM input (tach signal) is taken from the output of the stock ignitor right where it goes to the coil (there is a 1k resistor built into the coil that reduces the ignitor output so the meter can handle it). If the ignitor is "leaky" then the tach pulses go haywire - the leaked pulse may not be strong enough to charge the coil to cause spark interference... yet....
Re: RPM going crazy after 3k
Posted: January 20th, 2008, 9:14 pm
by Mooneggs
I agree with Shameem's diagnosis. This tach jumping has happened to me as well and it was related to the HEI mod tach wire resistor being loose because of my poor wiring skills lol
Re: RPM going crazy after 3k
Posted: January 22nd, 2008, 4:23 am
by Domino81
I've had something... sorta similar happen. Twice actually. Once the connection was loose with the HEI module. So the RPM's kinda.. twiched as I was driving on the Thruway to Rochester. It was irritating as hell. The HEI mod is super simple, really fairly cheap. PRD makes a modified distributor cap. I have a Blaster SS coil.
http://www.prdonline.com/catalog/produc ... ucts_id=28" onclick="window.open(this.href);return false;
The other was due to the wrong guage cluster. Wouldn't read the RPM's right at all. I'd poke around the ignition first.