4.0HC coughs at 1500rpm

[tops2]

My 4.0hc coughs at about 1200rpm to 2000rpm at a constant throttle , pulls clean when under load, the tick over is also a little lumpy and the pulgs are dark but all the same
The car had a flat battery for a good few weeks and i was told it could be that the ECU has lost its memory and it has to learn again. It has done a good few miles now but no change, all pipes/ electrical connections seem fine it also has new leads.
Any Ideas?.

[jonnyb]

Ill be the first then: Clean the stepper motor!

Details in the bible, although it sounds like its running a bit rich.

[tops2]

cleaned the stepper ,done the idle valve, airmeter.Cleaned the plugs which where black (rich),it has new leads, held every lead off and all o.k.
Vacuum Advance?.

[tops2]

Oh and unplugged the ECU.

[HarryW]

Has it always done it or has it just developed the problem , only ask as its not unknown for some cars with wilder cams not to be happy with light loads/speeds.
Mine hates 1600-1800 rpm for instance .

[tops2]

No according to the owner.
The car was in heated storage for 2 months and the battery went flat.
could the ECU have gone back in default mode and need some time to learn again?.

[tops2]

Funny it is about 1600- 1800rpm when its is bad, it ticks over quite lumpy as well.

[HarryW]

Can I assume you are the new owner then . Mine has always been a bit shunty at light load and trust me it has been fettled with more than once, it could just be normal for the car and the previuos owner was used to it .
It could be the advance stuck, see if there is movement in the mechanism, however if stuck then they are normally very flat at low rpm and seem perfectly normal higher up the range.

[tops2]

Thanks will look at the dizzy in the morning, I believe there is a oneway valve on the vacuum which can be a problem ( I am reading the bible in front of me).
Yeh its always a little shunty and sometimes more so, pulls clean with the slightest load or road gradient, its just a constant throttle at that rpm.

[tvrbubblecar]

Distributor cap and rotor ok ?
Chris

[monaco]

Hi

My HC is exactly the same and has been the same for the five years I've had it, it's high lift cam that hates low rev's, simple to fix Keep it over 2000rpm, well over

I assume a total remap may help, but haven't got round to that yet.

[jonnyb]

monaco said:

Hi My HC is exactly the same and has been the same for the five years I've had it, it's high lift cam that hates low rev's, simple to fix Keep it over 2000rpm, well over I assume a total remap may help, but haven't got round to that yet.

mines like this as well, do your engine a favour and dont let it labour below about 2000 rpm.