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Type 3 very rough idle
samjo - January 19th, 2018 at 06:43 PM

Hi all,

I have recently replaced my vacuum modulator. I have also replaced the breather/overfill hose on the filler neck. Everything was fine for a while.

Now my car is idleing very rough when warmed up. compression is ok 115psi if i did it correctly. I have done the following
- adjusted valve clearance
- replaced spark plugs and leads (very worn and plugs where oiled up because of the modulator failure)
- refueled (wanted to make sure it wasnt just bad fuel. what I did notice that the overfill hose is not working properly fuel gushing out if filling to fast)

Any thought of what to do next to fix the rough idle? I have thought about removing in-tank fuel filter and putting in a new external one. and replacing vacuum hoses but I have a sneaky suspicioun that wont help either

Any thought are appreciated.



grumble - January 19th, 2018 at 06:53 PM

Have you checked that the idle solenoids are tight, they have a habit of working loose or the pilot jet air bleed hole in the carbs blocks up.

ACE76 - January 20th, 2018 at 12:02 PM

The breather hose from fuel tank on the 1970 Aust. model model comes standard with the amusing habit of emptying an alarming amount of petrol out under pass side when refilling in hotter weather and whacking the cap on smartly. This fuel is just what remains of condensate in the hose; the whole tank doesn't siphon through (tho' it can look like it).
In the 1971-on more-imported type 3's this problem was fixed.

You can experiment with re-positioning the hose (eg. remove all low points in its run: vapour can't condense there then) -- OR don't fill to brim; fill on colder days; rock car slightly to allow excess air out -- and put cap on after half a minute or so - while waving to/smiling at the line-up behind you (usually stops, or reduces the dribble).

Rough running when warm could be due to many causes. Check for vacuum leaks at manifolds; vac. hose/s to distributor (and both in correct positions if two) & vac-advance "can" itself; balance pipe between carbs and all connexions. etc.
Otherwise could be any loose or blocked jet (as suggested by grumble); sticking valve, bad s'plug or lead, flooding, stuck auto choke, idle-mix too lean, sticking/faulty mech advance unit, poor condensor; sticking/worn points etc. etc. etc!

samjo - January 21st, 2018 at 05:59 PM

Just fiddled around a bit and cleaned the carbs with carby cleaner. I think I have narrowed it down to cyl 3,4, as pulling those plug leads of the distributor has marginal effect, while pulling of cyl 1 or 2 plug lead causes the engine to stop. Hm. I hope I don't have to take the engine out as the top end was rebuild recently.

Given that it is most likely cyl 3 or 4 or carby for those, is it safe to assume that it is not the vac advance unit and most likely not a vacuum hose issue? I would assume that these issues would affect all cylinders. Solenoids seem tight and working (click when pulling the wire off).
I also tried stalling the engine by trying to stop air flow (cover both carbys with rag and holding down tight) I would expect the engine to stop but it didnt. maybe that is because I couldn't get a proper seal or because of an air leak. The engine does sometimes backfire.

Additionally, it appears that the choke plate is open on both carbys. even with the engine cold and off, not sure this is normal, although last few days were quite warm.

Given all the above is it ok to keep driving it (I use it to get to work twice a week) or is that not advisable.

vw54 - January 21st, 2018 at 06:43 PM

Check the balance line between the 2 manifolds to see if not cracked or flex hoses leaking

Also wind the electric chokes back to the off position so they don't close when the engine is cold you don't really need them in Aussie loosen the 3 screws and turn anti clockwise to turn them OFF

ACE76 - January 22nd, 2018 at 10:48 AM

If doing as vw54 says (good idea), don't forget to remove and/or tape the wires from + side of coil to auto chokes, so they can't short.

Issues with the vac-adv or its little hoses/connectors will affect the LHS only. It is very easy to check the vacuum-adv can, and should be simple to check the hoses (don't forget to check they are in the correct positions if there are 2; or any unused port is sealed off).

Intermittent backfire can mean lean-running (poss. vac. leak), or ignition system fault (intermittent loss of spark).
Also worth checking timing is not too retarded - should be AT LEAST 7.5deg BTDC static (up to 10 or even 12 may be OK, depending on other conditions).

samjo - January 24th, 2018 at 09:41 PM

After another check it turns out one of the solenoids was a bit loose. I also redirected the hose from the vac advance can to the carby. Guess I will go and replace that hose the ends are a bit widened by the looks of it.
Does anyone have an idea of the original sizes for the vacuum hoses (internal diameter).



vw54 - January 25th, 2018 at 04:19 PM

where are you located Samjo

samjo - January 25th, 2018 at 04:56 PM

On the beautiful Southern island

samjo - February 12th, 2018 at 11:37 AM

Hi again,

although it has improved a little bit by tightening the solenoids the car is still idling rough. I was wonderig if my fuel filter is clogged up. Seems to be the sock in teh tank ype filter. Hs anyone replaced that with a standard external filter? If so do I need any special parts and or seals.