Hunting Idle and Misfire

[robertbrook]

Hi,

I have just bought chassis 194 and it has. hunting idle and misfire.

The previous owner but 1 fitted an Accufab plenum and throttle body. Would this need mapping into the ECU? I have the original TB and plenum so can have that fitted to see if it solves the running issues

[David]

No ECU 'jiggling' would be needed (possible?).
I suggested to the previous owner that he swapped the throttle body back to original, so he may already have tried that. Ask him.
I know he had investigated the throttle-stop as causing a problem and that didn't help.

There is masses of technical information here for full-members, which you cannot yet access.

Best would be to 'upgrade' your registration to full membership now you own a 260.
Send a PM to Tim asking for a questionnaire and giving him your email address for reply. Membership is free to those already members of the MGOC, otherwise you would have to apply to join at least. If for no other reason, opening up the "treasure chest" of 260 information here is worth the £50 for MGOC membership. Club shop is then open to you too.

David

[robertbrook]

Thanks David. That is helpful and I will certainly email Tim. I am already an MGOC member

[Pete]

Robert the first thing you need is a scan tool to check for codes and fuel trim data.

[SCP440]

If you scan the car it would also be usefull to get live data, poor fuel pressure and/or a faulty Lambda are more easily spotted with live data.

Steve

[David]

As I said, if I were you, the first thing I would do is to ask the seller what he has already tried. Saves spinning wheels and going off in the wrong direction.

David

[robertbrook]

Again all good advice - thanks all. Am swapping back to original TB and plenum and will plug in tomorrow.

[OneSixty]

Again all good advice - thanks all. Am swapping back to original TB and plenum and will plug in tomorrow.

If you decide to run the car with the standard TB and the find the Accufab wants a new home…..:wave

[Jez Marsh]

Assuming the previous owner hasn't checked this then chek all rubber and plastics in the intake side that can go brittle and develop a sneaky crack and air leak at our advancing years.

[robertbrook]

Again thanks for all the helpful info.

I took the car to a local MG Rover specialist and it is indeed leaking air. Will hopefully be on the road soon and will then tackle the other bits starting with the alloys - not keen on the black!

[David]

Again thanks for all the helpful info.

I took the car to a local MG Rover specialist and it is indeed leaking air....
Have they said where? One of the most common air-leak sources is the PCV system, since the hose or rubber end elbow-joints tend to rot or harden, more so on earlier cars (which yours is I believe). The valve unit is a 90k mile replacement service-item.

If it is that, note that the padded pipe/hose and PCV valve are Mustang parts not MGR, but available from the USA or maybe from a UK Mustang specialist.
Part-numbers here: https://www.two-sixties.co.uk/mgoc260/html/f0rum/showthread.php?19048-PCV-valve-and-Hose

David.