Speedometer jumping and a bit fast

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CR929
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Speedometer jumping and a bit fast

Post by CR929 »

Hi folks! Got a bit of a speedo issue here... I've done the search but my trouble is two in one so perhaps something else.

Got a 1990 Mk2 Japanese import (rev 1 I guess?), both issues appear at high speed. 1. The speedo shows a bit higher than actual speed, I am driving 70 and the GPS shows 53, trucks overtake me... and 2. Every couple of minutes the speedo jumps backwards for a split second, to immediately return to its original speed.

I've been thinking smaller wheels (bought the car this Sunday, all wheels are 195/50R15) but that doesn't solve jumping needle. The two options I now have are either the cable going out which I've seen to be the issue with others or some sort of conversion during import?

Thanks in advance for the help
Last edited by CR929 on 01/01/24 20:38, edited 1 time in total.


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peteV6R5
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Re: Speedometer jumping and a bit slow

Post by peteV6R5 »

REV1s came with 15" wheels and cable driven speedo, Rev2 onwards were electric speedos.

from previous owners think your cable (in 2 parts) is getting past its best and sticking causing your issue. or the speedo drive in the gearbox has worn out.
you can test the cable with battery drill before buying replacements.
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CR929
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Re: Speedometer jumping and a bit slow

Post by CR929 »

Hi Pete,

Thanks for coming to the rescue! I've scrolled through the manuals on the forum but couldn't find one for the speedo cable. I'm confident with electrics but not so much in diving into the engine bay myself to work stuff out and break something else in the process. Someone's obviously done it, are there any guides to this?

Cheers.

BYRNEY1984
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Re: Speedometer jumping and a bit slow

Post by BYRNEY1984 »

Rev 1 had 14” wheels. Rev 2 onwards where 15”along with bigger brakes etc. if its a 1990 same mine its a cable driven speedo. Have a look on top at the rear of the gearbox you’ll see the cable. Most likely the plastic gear on the sender is failing. Hence the jumping and reading wrong. The teeth will be worn. Have a look and if you need a sender I have a couple in the shed you’re welcome to one.
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Re: Speedometer jumping and a bit slow

Post by CR929 »

Thanks Alan, I'll probably have a look today if I don't freeze to death and will report back
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Re: Speedometer jumping and a bit slow

Post by peteV6R5 »

BYRNEY1984 wrote: 30/11/23 12:00 Rev 1 had 14” wheels. Rev 2 onwards where 15”along with bigger brakes etc. if its a 1990 same mine its a cable driven speedo. Have a look on top at the rear of the gearbox you’ll see the cable. Most likely the plastic gear on the sender is failing. Hence the jumping and reading wrong. The teeth will be worn. Have a look and if you need a sender I have a couple in the shed you’re welcome to one.
OMG shows how long been away (4 years) forgot REV1 had 14"s my bad :crybaby:
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Topic author
CR929
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Joined: 29/11/23 12:48
Current Model: MK2
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Real Name: Ivan
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Location: Bristol

Re: Speedometer jumping and a bit slow

Post by CR929 »

Thanks a bunch folks. I'll report back in January when I get myself a decent jack and axle support to have a look at the underside - can't reach the thing from the top for the life of me...
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