Another rough idle thread - Tii with 123

[pehlivanov_tii]

I read many threads, tried some things without success. My rough idle comes with random “clank” noise in the first cold minutes of idling, then it seems to disappear. The noise and the rough idle can be heard in the video.
Details about the car:

Rebuilt engine, rebuilt injectors, new 123 distributor (bluetooth version). KF pump is with new seals, bench tested and the output fuel is equal for all 4 cylinders.

 

what i tried so far:

- checked the length of the rods of the mechanism - it is ok

- tried to move the screws in the tuna can - not much of a difference

- tried two different curves in the 123 app, the stock one and slightly modified, i couldn’t see much difference

 

My mechanic is suspicious about the 123 distributor. If the timing is correct (he checked those things already) is there anything else that could go wrong with the distributor?

The vacuum which cannot be seen from the video - throttle body is linked with the distributor. Is it possible the not attached air box with the vacuum that will be linked to the valve cover to make such difference?

any thoughts?

thank you, guys!

 

[Mike G]

There’s fuel coming from the front left line on the kfish, is that from prior diagnostics or was that line not tightened down?

[pehlivanov_tii]

It needed extra tightening, yes, i did it, but that didn’t fix it

[Mark92131]

The throttle linkage to the K-fish has a lot of sloppy movement.  The idle seems low and lumpy (stock cam?).  I would verify that the 123 distributor ignition map is synced with the engine timing by setting the map to 25 degrees at 2500 and then use a timing light to verify the "BB" on the flywheel while holding 2500 RPM.  No "BB" in the viewing port, turn the distributor until is appears while holding 2500 RPM.  Then you'll know the map timing will be right.  I would also try more advance at idle to see if it smooths out a bit.  Then I would check for vacuum leaks.  Publish you current ignition map.

 

Mark92131

 

 

[pehlivanov_tii]

@Mark92131

here is my current curve. I tried the stock 123 curve too. What exactly do you mean by BB? Sorry for the dumb question, i am just trying to forward as much details i can to my mechanic who doesn’t have experience with such distribitutors.

Edited May 12 by pehlivanov_tii

[Mark92131]

2 minutes ago, pehlivanov_tii said:

What exactly do you mean by BB?

 

The steel ball on the flywheel at 25 degrees BTDC.  You should be able to see it with your timing light down the viewing port at the back of the block.

 

Mark92131

 

 

[dlacey]

6 hours ago, pehlivanov_tii said:

My rough idle comes with random “clank” noise in the first cold

That clank sounds like "front firing", meaning the mixture in the inlet near the injector is being ignited (opposite of backfiring when mixture ignites in the exhaust). 

[Mike G]

It’s either running roughly on all four cylinders or only on three, hard to say. Are the spark plug wires on the correct order?

 

here’s my 123 curve 

 

if the screws in your tuna can made no change something is really wrong, I can make my idle zing all over with them. Here’s my favorite simple adjustment guide 

you said the clank goes away after a few minutes, does the idle smooth out once the engine is warm?

 

 

Edited May 12 by Mike G

[Mike G]

2 minutes ago, Mike G said:

Nt 

 

 

Edited May 12 by Mike G

[SydneyTii]

I’d put the original distributor back in and try to run it with that, gives you somewhere to start.

[Aaron R]

Have you checked fuel pressure at the k fisch pump? Could be a weak electric pump 

[pehlivanov_tii]

@dlacey yes, it sounds like it is from there

@Mike G yes, I checked the spark plug wires. About the clank noise and the rough idle, the rough idle is constant even after the disappearing of the noise. Thanks for the good article, it will be definitely helpful once the bigger problem which I obviously have is solved.

@Aaron R yes, the fuel pump is brand new, I checked the pressure and it is ok, also the engine is starting to work a bit better when it's under load (when more fuel is needed)

@SydneyTii yes, I think I found one distributor from 2002, not a tii, but I guess it will still do the work for the test

[Son of Marty]

Pull the plugs and examine the porcelain right where it meets the steel screw base sometimes they will break loose and leak.

[Pablo M]

On 5/12/2024 at 10:39 AM, pehlivanov_tii said:

@Mark92131

here is my current curve. I tried the stock 123 curve too. What exactly do you mean by BB? Sorry for the dumb question, i am just trying to forward as much details i can to my mechanic who doesn’t have experience with such distribitutors.

I had issues when I installed my 123+ recently as well. I worked with 123 directly and their tech said, for my 72 tii, that it needed more advance in the lower rpms. Yours looks like mine from 1500 up, but he had me do 12* at 500, 15* at 1000, then 18* at 1500 and the rest upwards as you have it.
Try that and see if that helps. 

I also noticed on mine, that when cold, I have a vacuum leak at the WUR, but it goes away when warm. I confirmed this with a smoke test. 

[zinz]

You must confirm your 123 timing with a timing light.  Finding the green light on the 123 during installation is simply not going to be spot on TDC. I’ve installed many 123s over the years and they all need a bit of tweaking to get them correct. Once the 123 is confirmed to be delivering spark at the correct advance/rpm, then you can lock it down and trust the curve numbers. 
 

Ed