Tach. Jumps any advice ?

Reply Subscribe

Thread Tools

Search this Thread

Oct 29, 2003 | 11:32 AM

Richard Lang

Thread Starter

Addict
Rennlist Member

Joined: Jan 2003

Posts: 314

Likes: 0

From: Phoenix AZ

Tach. Jumps any advice ?

Sometimes on a quick run up ( acceleration) The Tach will jump from 4000 to 5000 , or 5000 to 6000 . Has the same feel as no Timing belt. Belt was changed 2,500 mile ago and retensioned 1,000 mile ago.

Any advice would be appreciated. ( 83 928S 5 speed )

Richard

Oct 29, 2003 | 12:35 PM

ViribusUnits

Nordschleife Master

Joined: Aug 2002

Posts: 9,010

Likes: 2

From: South Texas

What do you mean has the same feel as no timeing belt?

Ie no power?

Or something else?

Oct 29, 2003 | 12:44 PM

MikeN

Three Wheelin'

Joined: Jan 2003

Posts: 1,447

Likes: 0

I'll second that notion......what are you talking about?

My first guess would be a slipping clutch. If the engine is actually revving
faster (the tach is telling the truth) but the car is not moving faster......the most likely problem is a clutch disk/pressure plate going bad.

Oct 29, 2003 | 01:16 PM

Lizard928

Nordschleife Master

Joined: Apr 2003

Posts: 9,601

Likes: 39

From: Abbotsford B.C.

if the tach is jumping around I would check all the connections at the coil and the tach,
also measuring the voltage at the coil

Oct 29, 2003 | 03:30 PM

Richard Lang

Thread Starter

Addict
Rennlist Member

Joined: Jan 2003

Posts: 314

Likes: 0

From: Phoenix AZ

Thanks for the replys,

Mike , I think that is a great idea , I will check the clutch and pressure plate, that is the feeling the car reves but no power to the wheels.

It is time to start the winter projects anyway.

Thanks

Richard

Oct 29, 2003 | 03:43 PM

SteveCo

Addict
Rennlist Member

Joined: Jul 2002

Posts: 383

Likes: 1

From: St. John's, NF, Canada

A friend, who used to own a Ferrari dealership, once taught me a good, quick test for a slipping clutch.

Stop the car on level ground and select the highest gear (happened to be 4th he demonstrated on). Take your foot off the brake (don't set the parking brake either) and slowly let the clutch pedal out...just like you would to take off. The engine should die swiftly and quickly without any bucking or other unpleasantness. If it protests in any meaningful way, it is a good indicator that the clutch is not biting as it should and needs to be inspected further.

I have used this technique on several vehicles and it is very accurate. Certainly engine reving under load in higher gears is as well, but this method works when you cannot do this.

Hope this helps.

Regards,
SteveCo in St. John's

Reply Subscribe