d1 hesitating/stammering/surging part throttle

[starky]

Just spent bulk coin on my disco.

3.9 died a horrible and torturous death. so hello 4.6.
I was not happy with the power increase so i ordered from RPI an ignition upgrade kit which consisted of a
New dizzy, coil and magnecore leads.
Ignition amplifier.
Fuel pressure regulator.
upgrade from the super unreliable 5AM to the P38 20AM air flow meter.
And a Tornado chip form Mark Adam's.


Results:

Under hard acceleration Fantastic smiles all round.

normal driving Rubbish when you are coming to cruise speed and you start backing off throttle to attain correct speed the car surges kind of simlar to pulling a heavy trailer that is bucking around.

every now and then at very slight throttle it cough's as it is surging.


Help please this is giving me grey's

[98discovery]

Hi
I had similar issues with the standard 3.9 V8 setup when I bought it a few years ago and traced it to a combination of two things-
1.Idle mixture on MAF set very lean.
2.Timing needed advancing.
After adjusting these the problem disappeared and has not returned
Hope this helps

[bee utey]

Try disconnecting the vacuum advance. If that fixes it you may have either too much advance or a misaligned pickup in the distributor. Check the tip of the rotor button very carefully and see if the burning is consistent across the whole edge or just at one corner. If it's at one corner it means the vacuum advance is moving the rotor away from the cap terminal into clear space at light throttle. I've met this more than once!

[starky]

Thanks guy's i will try this today.

I was told by mark adam's to lower the fuel pressure to 36Psi but this made it much worse so i went the other way and it got better my fuel is currently set at 50 Psi which is giving the car huge power but it is still got a slight hesitation at part throttle