Rev Counter / Tachometer Prob

[solarice]

Hoping someones got an idea whats up...everything was fine before had and since installing everything back into the engine bay and starting the car the rev counter is bouncing about, jumping to 3k then back to 1k idling then repeats...had a search on here but havent found a similar thread.

It also seems late in responding to revving...did the haynes ecu check method and everythings coming back as fine. Checked all the wiring no obvious probs, the alternators currently off the car aswell...apart from that everythigns the same.

any ideas where the bad connection is ? probably somthing simple that ive overlooked.

Cheers,
Kris.

 

[ollyc98]

My aftermarket one did it, earth problem.

 

[Demarest]

Hoping someones got an idea whats up...everything was fine before had and since installing everything back into the engine bay and starting the car the rev counter is bouncing about, jumping to 3k then back to 1k idling then repeats...had a search on here but havent found a similar thread.

It also seems late in responding to revving...did the haynes ecu check method and everythings coming back as fine. Checked all the wiring no obvious probs, the alternators currently off the car aswell...apart from that everythigns the same.

any ideas where the bad connection is ? probably somthing simple that ive overlooked.

Cheers,
Kris.

I had something similer to this the other day with my added super s counter on my L model,
it started bouncing around 2.5K then up to 3, 4, and 5, was a hot day so maybe the temperture had a part in this

I thought the problem might have been mis-firing, or a problem with the halfords distrubuter cap, when i opened the bonnet the signal wire was running on top of the distrubter cap, so maybe electrical interferance, i thought,

so i moved it away from the distributer cap as far as i couldt and had no further problems

so it could be electrical interference from distributer cap, mis-firing, or something else

 

[zanes]

Voltage reg problems?

 

[solarice]

bit of an update turns out it was the dizzy (engine probs included erratic tach, rough idling, air escaping back into the inlet)...though not a common fault so i doubt this will help anyone in the future unless you do what i did

as it happens id rebuilt the dizzy before hand and id made a little error theres a timing disc that the ecu uses to check revs etc, well it put that back in backwards meaning it was reading 180 degrees out...so seemed to be firing when inlet valves were open and generally screwing everything up.

once i switched it around all the probs have gone and the engines running sweet...so for anyone who dismantles the dizzy make sure you put it back correctly ("well never" i hear you say) lol

cheers for the ideas though people...