72T Rough over 3K RPM

LeeD · 12-01-2021, 01:13 PM

I just completed a standard service on my 72T (Oil change, valve adjustment, spark plugs) and since the service, the car has been running rough over 3K RPM. It does seam to smooth out over 4K. I have checked timing and replaced the points on the car.

Any clue or guidance on what I should look at next? Is there anything else that I can or should check?

Thanks, Lee

Jeff Higgins · 12-01-2021, 05:15 PM

Which induction system is it running?

LeeD · 12-01-2021, 06:51 PM

Standard Bosch MFI

timmy2 · timmy2's Garage

I think he was asking about fuel. Carbs, MFI or?
That rpm is a transition zone for fuel system and distributor weights…

LeeD · 12-01-2021, 07:23 PM

I have the original MFI and using the standad Bosch distributor with points. Did I answer you questions?

Demetri · Demetri's Garage

I had a similar situation not long ago and it ended up being a broken spark plug. Broken at the insulator.

timmy2 · timmy2's Garage

Check everything you worked on if it wasn’t doing what it is now doing, before your service.
Loose plug wire, new points still clean after sanding, dwell etc.

GaryR · GaryR's Garage

Quote:

Originally Posted by timmy2

Check everything you worked on if it wasn’t doing what it is now doing, before your service.
Loose plug wire, new points still clean after sanding, dwell etc.

^^^^^^^^^^^
Yes, the chance of it being something you didn't mess with is low, so go over everything you did before you start messing with new things and end up down a rabbit hole..

LeeD · 12-02-2021, 01:24 PM

Thanks, that I have done but will triple check everything again. I should have also said that I had this problem before I did the service (especially in 2nd gear), but seams worse after the updates.

GaryR · GaryR's Garage

Quote:

Originally Posted by LeeD

Thanks, that I have done but will triple check everything again. I should have also said that I had this problem before I did the service (especially in 2nd gear), but seams worse after the updates.

That's a big bit of info right there...

In that case, if it is smooth running before that point I would look at the distributor not advancing properly. Magnets, springs, bearings, vacuum (assume it is vacuum driven?)..

tobluforu · tobluforu's Garage

It's time to CMA. When you adjusted the valves, were they loose or tight to begin with? Lots of cross talk in regard to valves, should they be loose, tight. Most say they should be on the looser side of things; some will say if they are a tad tighter then it will run better. Go figure. And I use those terms, loosely, no pun. My 72 has always been weird around that rpm.
Good luck.