180mph from warm start

[TOM500]

Sounds like an improbable claim and sadly it is.
It's actually a gripe with the speedo. It's happened couple of times now that after letting the car warm up on the drive then setting off, the speedo leaps right round past the maximum speed and stays there at all speeds over a crawl. When i stop at lights/junctions etc it flicks back round to 0. The odd thing is that when I switch the ignition off (for example at the petrol station) and turn back on it then works normally.
The car does sit for a week (sometimes 2) at a time between drives and i wondered if anyone else had this problem and knew a simple cure. Also I'm worried that this problem may be damaging the tacho's more sensitive bits. Any advice much appreciated.

[225]

Very common problem. Have a search through the Chim forum, theres a sensor somewhere which goes a bit doolaly sometimes but someone more technical than I will doubtless explain!

[jellison]

I recon mine would just pull that in fifth (from a standstill) if I had a down hill start when rev limit is upped to 6750 (in a month or two) - only geared for about 175 at the moment!

[Briefträger]

Oh god, YAWN don't you ever learn,You are a very boring man, whoopee doo do you have put a BIG ENGINE in your Chimaera, I’m sure they know all about the MONSTER in Outer Mongolia

[Cider Andy]

It's likely to be the speedo unit itself, or the sensor/pick-up, as 225 says. For cars with the Borg Warner/Tremec T5 gearbox the sensor is just off the diff end of one of the driveshafts. (For the earlier Rover SD1 'box, I believe it's just off the 'box itself). Apparently they're sensitive to the ingress of dirt: cleaning it can sometimes cure the problem.

The speedo itself is electronic and can be repaired. Try a search in this forum; there was a thread in the last few months covering this.

[TOM500]

Thanks for the advice. Think I'll start with giving it a clean and see what happens.

[Tafford]

I had a similar problem (only even faster!)which turned out to be the speedo - see thread www.pistonheads.com/gassing/topic.asp?h=0&f=8&t=211268. I had to send the speedo away to get it sorted

[jellison]

[quote=Briefträger]Oh god, YAWN don't you ever learn,You are a very boring man, whoopee doo do you have put a BIG ENGINE in your Chimaera, I’m sure they know all about the MONSTER in Outer Mongolia[/quote]As a newbie (yes you've been watching from afat - might well be the best place for you) - why don't you just join in the fun and stop being a kill joy like some many on here now - Muppet!

TOM - try pulling the connector from the diff sensor apart clean it and reconnect. Might sort.