Advice please - engine judder on constant throttle?

[dickieandjulie]

Hi all - I wonder if anyone can help.

The engine has taken to juddering/hesitating when on constant throttle. Its fine when gunning it! The stepper motor has been cleaned, air flow meter adjusted and stp fuel additive run through it.

Does anyone have any suggestions what it might be as I need the car this week nd therefore cant drop off at Austecs for them to look at?

Cheers

Richard

[l33]

Running rich, Air leak, is the cam worn...

Could be a few things. There are a few threads here if you search. how does it idle? Does it hunt?

I had the same problem and rather than solving it changed the engine! I am sure a fix is far simpler however...

[dickieandjulie]

It only had a new engine 10k miles ago so the cam etc should be fine?! Not hunting at idle either?

[l33]

dickieandjulie said:

It only had a new engine 10k miles ago so the cam etc should be fine?! Not hunting at idle either?

In that case, if it was running fine, maybe a small air leak has developed or a bad earth or loose connection somewhere?

There are many more knowledgable people than me on this site who may well have a different opinion or be in a position to point you specifically.
L33.

[dickieandjulie]

Thanks for your help - got it running now and it is definitely NOT running steady at idle, does not stall but varies in tickover rate

[TVR 3X]

Try reseating the resistor pack connection.

On my car (flapper injection) this is a cigarette pack sized box mounted on the nearside inner wing with thickish wires and large white connection.

Russ

[number 7]

Worn track on the throttle pot maybe?

7.

[chunder]

Sounds like may be running lean at cruise - was the ecu fuelling set up when the new engine went in ?

A minor air leak may cause hunting at idle but wouldn't have thought it would lean things up too much when cruising, unless the stepper motor is doing things it shouldn't.

If the stepper motors ok and the fuelling has been ok previously then as suggested check throttle pot, also coolant sensor and fuel pressure worth checking (also vac advance ?).