Engine start to run really rough today

[Nel]

Hi, I'm looking for advice on what to look at since car start to run really rough today and seem to be getting worst.  It's a 1970 340 no mod at the electrical parts and a Fitech Install about 2 months a ago. It's running like the fire is cutting out and wen you press the gaz it feel like it doesn't want to take it.

On the Fitech screen the rpm is bouncing all over the place at idle and driving too. Like if your are cruising, its running rough and the screen show the rpm bouncing from 2000 to 4000 and all over.

[GoodysGotaCuda]

Datalogs may best show exactly what the RPM is doing, the FiTech screen refresh rate is fairly slow.

Assuming the rpm isn't actually cycling from 2000-4000 but the fitech says it is, that sounds like a tach noise problem. The wiring going from the distributor to the FiTech is very sensitive to RFI/ignition/electrical noise. Throughly look at that part of the harness for it's proximity to ignition components and spark plug wires. It's not uncommon to need to extensively shield those wires from noise. Copper tape wrapped around those wires and grounded to one end is one solution I have used.

[70Barracuda]

Which ignition are you running?

[Nel]

All stock ignition.  We found big part of the problem today, the timing cover was loose  and the vacumm hose that goes to the timer was all dry out. It's running better now but still hesitate if  you press the gaz quick. Has for the rpm I will check the wire.

Thank you I never tough about noise. Would that make the engine hesitate?

[70Barracuda]

Your ignition system cannot run EFI clean.  Mine did the same thing, it ran well until I got into it then it would fall on its face.  The tach noise is too loud for EFI.  When I went to a ready to run distributor it ran great.
IMO you have to go with an aftermarket ignition system.

[70 Challenger Lover]

You will be thrilled with the improvement of a modern ignition system versus the crappy old setup. If I went to all the trouble and expense of an EFI upgrade, I wouldn't hesitate to upgrade the whole ignition. You might even be able to integrate the two systems for even better performance.