Diagnostics - a separate issue

[Griffter]

Re this post: www.pistonheads.co.uk/gassing/topic.asp?t=282794&f=9&h=0

On a separate note, on occasion I hit what seems to be a rev limiter at about 4.7k rpm. Once it had happened, this was repeatable and consistent. Disconnecting/reconnecting the battery 'solves' it.

Does the 14CUX have a 'limp home' map?
How does a precat (open loop) ECU know to switch to limp home mode?

[GreenV8S]

Griffter said:

Does the 14CUX have a 'limp home' map?
How does a precat (open loop) ECU know to switch to limp home mode?

Yes and yes. No mode has a rev lim set that low though, as standard. Was it a hard cut-off like a rev limiter, or a misfire that got progressively worse with revs?

[shpub]

Yes it does as you can disconnect a lot of sensors and the engine will still start. Resetting the ECU will restore the defaults and the ECU will start to adapt. If the sensors are out of spec i.e. providing valid info but the wrong values this can lead to the ECU screwing up over time. There will be no fault codes as the info will be wrong but not out of spec.

[Griffter]

GreenV8S said:

Griffter said:

Does the 14CUX have a 'limp home' map?
How does a precat (open loop) ECU know to switch to limp home mode?

Yes and yes. No mode has a rev lim set that low though, as standard. Was it a hard cut-off like a rev limiter, or a misfire that got progressively worse with revs?

Hard cut-off. Definitely persistent and consistent, until I disconnected/reconnected the battery. EPROM not standard it seems - courtesy of Mark Adams during previous ownership. Maybe he set the default limp home rpm limit that low? Has only ever happened following the 'misfire' problem in related thread. Maybe the ECU detects different injector signals per bank and knows something's wrong... I can only remember it doing this 'rev limiter' thing twice in 3 years - but once it does it, it does it every time the revs hit 4.7k - until I disconnect/reconnect (or maybe switch off ignition, I guess).

[pupp]

Any fault codes showing when it does this?

[Griffter]

pupp said:

Any fault codes showing when it does this?

Don't know. I planned to go to the local LR/RR specialist to find out, but then I rememebered I'd reset the ECU. Doh!