Grunting and puffing below 4000

[moggsie]

My lovely 4.2 cerbie is atm not very well.
Since being to a garage, who have experience of TVR's, too have the seal and bearings replaced in the gear box, she coughs and splutters below 4000rpm as though one side of the engine has been removed. The moment you get above this limit it is like pouring petrol on a fire - she takes off like she is supposed to.
The only thing the garage can come up with is that they took of the cables to the lamda censors and have incorrectly reconnected them as the only other thing they did was to give the lump an oil change and new filter.

Does this sound like it could be the case?? Could the ECU have been knackered when the battery came off?
Now ordinarily you would take her back stright away but I live in mid wales and it is a two hour trek back so would prefer to ask a local garage to swap the leads or, do it myself!!

Any thoughts chaps!

btw - if you really want a good day out with your cerbie - bring it over here where I live, roads are good and pretty empty of traffic. Just perfect

[simonsparrow]

Could be a number of things, but below 4000 RPM, the lambda sensors are used to adjust the fuel mixture. Throttle pots and an inbalance between banks can also help produce these symptoms.

[danfrith]

defo sounds like one of the lamba sensors has failed! get it checked out, if you get stuck in traffic the cats could start glowing red, and catch the body work alight! as the right mixture isnt being achieved!

[350matt]

If they've plugged the LH bank sensor into the RH Exhaust and vice versa this would screw things up nicely, you can check this yourself but you will have to remove the wiper cover.
The wires are labelled odd and even bank and should match those on the TPS.

Matt

[moggsie]

danfrith said:

defo sounds like one of the lamba sensors has failed! get it checked out, if you get stuck in traffic the cats could start glowing red, and catch the body work alight! as the right mixture isnt being achieved!

Thanks, the mechanic did say one of them looked past its sell by date so can I check this out with this software I keep hearing about and if so where can I get it.

[moggsie]

350matt said:

If they've plugged the LH bank sensor into the RH Exhaust and vice versa this would screw things up nicely, you can check this yourself but you will have to remove the wiper cover. The wires are labelled odd and even bank and should match those on the TPS. Matt

Hey Matt,

Thanks for the reply but TPS??? sorry. Lots to assimilate with a cerbie in a short space of time. They do demand this of you don't they!!!

[Toady1]

TPS = throttle position sensor.

[moggsie]

Toady1 said:

TPS = throttle position sensor.

ta