11 hours ago, Joja2k said:

Quick new update, after restarting the car, there is now noise coming from the engine bay, but I can't decide if it sounds like rattling, knocking or pinking.

As @nta16 says, without starting the cold engine, set the valve clearances, contact breaker point clearance and static engine timing.

Now start the engine and run until hot. Maybe a 10 mile or so run at your extra-urban speed limit.

Now, and only now, adjust the carburettor idle stop to get the slowest smooth idle speed. Do not look at the tachometer whilst doing this (I've done it on cars with no tacho).

Adjust the dwell angle to get the fastest idle speed by ear. You don't need a dwell meter. Now slow the idle speed to a slow smooth idle again.

Am I going crazy or was there another post saying the car is now running X10 worse that isn't showing now?

If the car is now running worse then there are several routes you can take. Firstly was this tachometer jumping and/or misfire present before you started changing these parts or was it introduced by the change of a part(s) as this would suggest which route(s) you take.

a) You could put all the old parts back on and change one part at a time.

b) Or you could fit the new module as you have it and it is one of the few parts that hasn't been replaced.

If the car isn't running X10 worse then as Paws4Thot has put but if you set the valve clearances cold only 2,000km ago you can skip that.

Personally I would put in at least a temporary additional large earth cable to the engine after drop testing the earth from the battery as far back as I could go through the ignition system, confirmation generally needs testing/checking and cross-checking, assumption and guessing often comes back to taking a chunk out of your posterior. One plug, lead, cable, wire connector/connection can often be an issue cause.

Not be pessimistic now so don't get dishearten as I am only considering possibilities. Always consider that the tacho jumping and misfire could be two separate issues though they could combine, don't assume if you have sorted one that you have sorted both (though that could be the case you don't know until testing, which might be use of the car) and of course don't assume the the tacho and misfire are the only issues, they could also be masking another/other issue(s). Again these are possibilities and it might be you have only one issue to resolve.

Even with complicated issues you should always start with checking the basics and later rechecking the basics, not always but more than enough times complicated issues are resolved by checking (or rechecking) the basics. For me with electrics/electronics that starts at the 12v battery and the battery terminal posts and cable clamps, battery fully or reasonably charged, terminals and clamps clean and secure and then work forward from there as required.

12 hours ago, nta16 said:

many p1ss-poor, rubbish built Chinese ignition parts

After what happened to me with VIKA rear windscreen wiper motor i don't want to buy any crucial (especially electrical) part again.

On 19/04/2025 at 14:14, Joja2k said:

Hello everyone, as the title itself says. The tachometer on my Favorit started going crazy but I can't see where the problem lies. Here are a few words on the issue; When the car is idling and you press the throttle everything seems fine until the engine reaches some 2500 RPM, the tachometer then jumps all the way to 8000 RPM and bounces back. While driving the car every time I shift gears the tachometer bounces up and down to about 3500 RPM (I shift gears anywhere from 2000 to 2500 RPM) How can I fix this issue? Any help is valuable!

@R_Blue had this exact issue and solved it

Hello again,

Today I bought a timing light, this one;

https://www.kroftools.com/en/regulation-and-test/digital-display-timing-light_p1781.html

Should be more than enough. I'm gonna try to set the timing today or tomorrow and will keep you updated. Sorry for not responding but I didn't have any time to work on the car as I was harvesting honey with my brother.

Cheers!

On 03/05/2025 at 06:26, Paws4Thot said:

As @nta16 says, without starting the cold engine, set the valve clearances, contact breaker point clearance and static engine timing.

Now start the engine and run until hot. Maybe a 10 mile or so run at your extra-urban speed limit.

Now, and only now, adjust the carburettor idle stop to get the slowest smooth idle speed. Do not look at the tachometer whilst doing this (I've done it on cars with no tacho).

Adjust the dwell angle to get the fastest idle speed by ear. You don't need a dwell meter. Now slow the idle speed to a slow smooth idle again.

Is the procedure the same with the timing light?

8 minutes ago, Joja2k said:

Hello again,

Today I bought a timing light, this one;

https://www.kroftools.com/en/regulation-and-test/digital-display-timing-light_p1781.html

Should be more than enough. I'm gonna try to set the timing today or tomorrow and will keep you updated. Sorry for not responding but I didn't have any time to work on the car as I was harvesting honey with my brother.

Cheers!

Is the procedure the same with the timing light?

No. A timing light is used for dynamically timing the ignition, usually at idle speed on a hot engine.

From memory, set the points gap and adjust the timing manually with the engine off.

Now mark the relevant timing notches on the crankshaft pulley and timing marks (on the block near the pulley) with white paint or typist's correcting fluid, and allow to dry.

This stage is best done in a dark area. Connect the light between the distributor cap and number 1 cylinder, then start the engine. Point the light at the timing marks, and look to see if the mark on the crank pulley aligns with the painted static mark. If it does, well and good. If it doesn't, adjust the distributor very slowly and carefully until they do align.

If I got this correct, the procedure on setting the timing goes something like this;

Locate the timing pulley on the timing chain cover.

Mark the V notch with white paint and set it to 0.

Connect the timing light.

Start the car and let it get to it's operating temperature.

Disconnect vacuum tube from the distributor.

Unscrew the distributor retaining bolt just enough sou you can rotate it.

Point the timing light to the pulley and "fire" the timing light at it.

If the timing is above 5 +- 2 (7) Degrees rotate the distributor (retard the timing), if the timing is below 5 +- 2 (3) Degrees rotate the distributor (advance the timing).

The timing should now be set correctly.

Tighten the distributor retaining bolt.

Connect the distributor vacuum tube.

Adjust mixture screw on the carb untill you get a smooth idle.

Is this procedure correct?

Ps. The Haynes skoda favorit 89-92 book says the timing should be 5 +- 2 degrees at 725 rpm (for my 136 engine).

Cheers!

Edited 7 May7 May by Joja2k

What about the "vacuum advance" that the manual is mentioning. How do I set that?

Here are the manual images:

https://postimg.cc/XB3pYQQQ

Album — Postimages

Album — Postimages

Edited 7 May7 May by Joja2k

26 minutes ago, Joja2k said:

If I got this correct, the procedure on setting the timing goes something like this;

Locate the timing pulley on the timing chain cover.

Mark the V notch with white paint and set it to 0.

Connect the timing light.

Start the car and let it get to it's operating temperature.

Disconnect vacuum tube from the distributor.

Unscrew the distributor retaining bolt just enough sou you can rotate it.

Point the timing light to the pulley and "fire" the timing light at it.

If the timing is above 5 +- 2 (7) Degrees rotate the distributor (retard the timing), if the timing is below 5 +- 2 (3) Degrees rotate the distributor (advance the timing).

The timing should now be set correctly.

Tighten the distributor retaining bolt.

Connect the distributor vacuum tube.

Adjust mixture screw on the carb untill you get a smooth idle.

Is this procedure correct?

Ps. The Haynes skoda favorit 89-92 book says the timing should be 5 +- 2 degrees at 725 rpm (for my 136 engine).

Cheers!

The only thing I don't get here is where should i set the static timing, to 0 or to 5 (before starting the engine (since the specs say "5 +- 2 BTDC"))

Edited 7 May7 May by Joja2k

It won't be 0, don't rely on Haynes to always be correct but if you take it as 5 plus or minus 2(?) then 3-7(?) (are the markings that accurate?). With rotor pointing to number 1, it might be more near rather than spot on on number 1. Same with will it actually idle smoothly at 725 rpm anytime, or perhaps higher or perhaps lower.

Berar in mind the Haynes refers to a factory car and settings from when the car was new, many things have changed since then and probably many miles on the engine, plus there may have been changes to or on the engine since the car lefty the factory.

The book figures are a very good starting reference, and might still stand, but the idea is to get the engine running well today as it is and with how things are today so don't be too slavish about book figures - and check and cross-reference the figures are correct, all data has errors and omission including Haynes (started by an English chap in the 1960s).

Check the Haynes, as I remember it you set up with the vacuum disconnected but it might not matter so much with electronic ignition, leave the vacuum on the middle (neutral setting) unless Haynes says different or you need adjustment.

Also, one more question. I have been searching for hours on the internet and am not succesfull. But how exactly do I adjust the carburettor mixture screw and the carb idle speed screw? (without a vacuum gauge)

Edited 8 May8 May by Joja2k

18 minutes ago, Joja2k said:

how exactly do I adjust

1. the carburettor mixture screw

2. and the carb idle speed screw?

1. These days, with a CO meter. It used to be possible to work by exhaust colour, but that needs leaded fuel.

2. By ear and/or a tachometer. Set the slowest speed where the engine idles without any sign of stalling.

I would have thought there might be some information here on setting the carb. You do need to give up more information, you have the car everyone else only has it in their imagination of the engine bay and its contents, you may have put up photos before in other threads but they are forgotten by me at least. Is the carb a factory fitted standard carb (make, model), are you on just petrol or LPG too.

For later, I too, for one, need reminding of your ignition set up, as it is now, my memory is you have got electronic ignition, cheap replacement dissy, new (undeclared make) HT leads, new (undeclared make and model) spark plugs.

There are photos and or videos of carbs here, one or some might be from you for all I know. Generally the engine running sounds smoother when the mixture is set richer so whilst you want to hear a smooth steady idle you need some instrument to confirm mixture for economical running at least.

Edited 8 May8 May by nta16
typos

Hello everyone,

I've got good news. I finally resolved the tachometer issue.

I will describe the steps below for anyone in the future;

The car was cold, so I opened the bonnet and set the valve cearances again (some were spot one, some valves were off by 0.1-0.2mm (how does that happen?))

After the valves have been set I did next:

NOTE: the timing degrees mentioned below are for favorit 136 engines, favorit 135 engine's specs for timing are "2 +- 2 degrees" so ideally on a 135 engine you would aim for 2 degrees."

Locate the timing pulley on the timing chain cover.

Mark the V notch with white paint and set it to 0.

Connect the timing light.

Start the car and let it get to it's operating temperature.

Disconnect vacuum tube from the distributor and plug it with a screw.

Unscrew the distributor retaining bolt just enough so you can rotate it.

Point the timing light to the pulley and "fire" the timing light at it.

If the timing is above 5 +- 2 (7) Degrees rotate the distributor (retard the timing), if the timing is below 5 +- 2 (3) Degrees rotate the distributor (advance the timing).

You need to aim for 5 Degrees ideally.

The timing should now be set correctly.

Tighten the distributor retaining bolt.

Connect the distributor vacuum tube.

Next in line is the carburettor.

Ideally you should use an external tachometer. My stroboscope has the said function so I used that for reference (the external tachometer needs to read at least 50 rpm changes)

The stroboscope I used:

https://www.kroftools.com/en/regulation-and-test/digital-display-timing-light_p1781.html

The steps are as described below:

Connect the timing light.

Start the car and let it get to it's operating temperature.

Set the read method on the stroboscope to rpm.

Adjust mixture screw on the carb untill the engine's rpms don't rise anymore then back it off a little bit (maybe by half a turn or less).

Adjust the idle speed screw untill the tachometer reads 800 +- 50 rpm (ideally you would set the idle to 850 rpm.

The carburettor should now be set.

Turn off the car.

Disconnect the stroboscope (timing light).

And voila, you are done.

Cheers!

Edited 10 May10 May by Joja2k

On 08/05/2025 at 10:10, nta16 said:

I would have thought there might be some information here on setting the carb. You do need to give up more information, you have the car everyone else only has it in their imagination of the engine bay and its contents, you may have put up photos before in other threads but they are forgotten by me at least. Is the carb a factory fitted standard carb (make, model), are you on just petrol or LPG too.

For later, I too, for one, need reminding of your ignition set up, as it is now, my memory is you have got electronic ignition, cheap replacement dissy, new (undeclared make) HT leads, new (undeclared make and model) spark plugs.

There are photos and or videos of carbs here, one or some might be from you for all I know. Generally the engine running sounds smoother when the mixture is set richer so whilst you want to hear a smooth steady idle you need some instrument to confirm mixture for economical running at least.

the ht leads are oe, tesla from czech republic. the carburettor is a jikov 28/30 LEKR and it's not set for LPG, just petrol. Later I will post an update about the consumption (l/100km).

PS. Old parts have been refitted (new parts are in my boot for an emergency?)

Edited 10 May10 May by Joja2k

Well done and thanks for reporting back fully. Perhaps you would like to put up your guides as threads/posts on the 'Classic Skoda Guides' forum. - https://www.briskoda.net/forums/forum/178-classic-skoda-guides/

It doesn't matter but I misunderstood your 5 and +/- 2, I was hoping the strobe light you bought had rpm too but didn't mention anything as you had already bought it and was having a hard enough time as it was without suggesting you might have need a different strobe light.

Some valve clearances being slightly different to when you lasted check will always happen with an old used engine as long as not too too many are to far out. The thing is just to be consistent with how you set all of them, different people have different ways and 'feel' to this, on these old engine design and builds it was never that critical or could be that sustainably accurate, the next time you run the engine there would be differences from when you set them. But they do need to be (about) right and consistent as they affect the set up and running.

Fair enough have the new parts in your boot until you have confidence in the running of the engine but don't be like the old-farts with old ("classic") cars that carry a car load of parts for breakdowns and "just in case" and because a certain part once let them down (usually because it wasn't fited right or replaced before it wore so badly - or was a p1ss-poor, crap made modern part). I ran "classics" (old over-priced and over-valued) cars for 30+ years for daily use and I knew of others owners that carried all sort of parts, you would need a trailer to carry all the possible parts. Prevention is better than cure, fit good quality parts correctly, use the car regularly (better still frequently) fully and properly service, maintain and repair as required the WHOLE car (not just the relatively unimportant engine. I used to change things like gearbox/transmission oil(s), (power steering for your car(?) despite "experts" (and engineers) saying not to bother. Brake fluid change, flush, clean. Initially (very) thorough clean, flushes and coolant change to cooling heating system.

Obviously absolute priority is given to the braking system being in good order and function, a very important component of this is the tyres (which are also important to the steering, suspension and handling, road holding, ride quality and noise of the car) this is not just how much tread depth is left on them but how old and hard they have got affecting their performance.

Also more important on an old car (and now more recent newer cars) is the 12v and its state of charge and health, for starting the car and running all the electrics but also for fault finding and repairs, particular engine starting and electric/electronic faults. So best to use the car regularly to keep the battery topped up (and for the sake of other (mechanical and other) systems on the car) - or if you really can't drive the car regularly over reasonable distances 30-50+ kms then get a battery charger maintainer. The little (low speed) drive you done on the video is fine after the engine has been fully warmed (at normal coolant temperature for a good number of minutes or 90+c engine oil temperature) as a test drive but no/very little good for the engine otherwise.

Once you have things sorted just routine servicing and maintenance may only be needed if you use the car enough to keep it from reverting back and it should get better running and more reliable. Of course there will be things that might go wrong but with regularly driving the car you will learn how the car is normally so hopefully tell when things start to go off normal, plus you will learn how the car could or should actually go, it should not fell like a museum piece. You will be a better driver in this than in a more modern car.

Good luck.

ETA: In my limited dealings with (twin) carbs (single carb was too long ago for my memory) despite what the book says I have never been able to noticed sound difference at 50rpm and for idle speed(s) usually you take the book figure as a starting point guide as the running might be better above this, it is no good having a good idle if the rest of the on the road running is not good. This is why you always do real world road driving to test and/or confirm your settings (even if the car is set up on a rolling road "dyno").

There are so many differences from when the car was new and left the factory to now, not least the aging, wear, tear, use and abuse of the car but also in the UK at least changes in the petrol coming out of the petrol station pumps. Somethings like oils have improved other things like some parts quality have not - buit that is the same for new cars too.

Cars are all about engineering and mechanical compromises, you can only hope to keep these compromises as small as reasonably practical.

Hello everyone,

Just a quick update. After adjusting the carburettor and the distributor I've driven the car 200 Km.

Just now I went to the petrol station and filled the car up with petrol. 19,58 L is how much the car consumed in those 200 Km.

I would say that is a very good result. The car is consuming just as much as when it was new.

Please note that my car has got 130000 ish Km on the clock.

Ps, I know I am young (about to be 23 years old) but I have driven a few cars other than the favorit. So far I've driven a Citroen C4, BMW 316d, Volkswagen Golf 8, Daewoo Matiz. And by far the Skoda favorit is the best car that I've driven. I absolutely adore the car. I personally think non of the cars mentioned above can compete in the pure pleasure that is Skoda Favorit to drive.

My Skoda Favorit is a 136 engine, from 07/1991, so probably one of the last Skodas to be made before Volkswagen bought Skoda.

Cheers!

Edited 13 May13 May by Joja2k

16 minutes ago, Joja2k said:

Hello everyone,

Just a quick update. After adjusting the carburettor and the distributor I've driven the car 200 Km.

Just now I went to the petrol station and filled the car up with petrol. 19,58 L is how much the car consumed in those 200 Km.

I would say that is a very good result. The car is consuming just as much as when it was new.

Please note that my car has got 130000 ish Km on the clock.

Ps, I know I am young (about to be 23 years old) but I have driven a few cars other than the favorit. So far I've driven a Citroen C4, BMW 316d, Volkswagen Golf 8, Daewoo Matiz. And by far the Skoda favorit is the best car that I've driven. I absolutely adore the car. I personally think non of the cars mentioned above can compete in the pure pleasure that is Skoda Favorit to drive.

My Skoda Favorit is a 136 engine, from 07/1991, so probably one of the last Skodas to be made before Volkswagen bought Skoda.

Cheers!

Also please note that when driving the car I like to keep the revs high, once the engine gets to it's operating temperature. Meaning if I'm driving 50Km/h I'm in 3rd gear and around 2000 Rpms etc. So regarding this information I think that the fuel economy is good.

Cheers!

Great news. With more running of the car and some fine tuning you may find you get even a bit better fuel economy.

And so good you find the car good to drive, unusual in someone your age but you are learning to actually drive rather partly at least relying on the car to do things for you and you will be learning about driver and owner maintenance of the car and vehicles generally, more so than many young qualified drivers.

Just to let you know 2,000 rpm isn't high revs so you might be better driving in 4th gear at 50km/h and using a little less petrol, 3rd gear for approaching hazards of course.

I lifted the following dash photo off the net of a 1991 Skoda 135 Rapid Coupe (135 RiC(?)) the 136 engine may vary slightly but it gives an indication of revs suited to the engine, note the green and red sections. Not that I would go much near or above 5,000 very often, other posters will know better than I where the 136 engine performs at its optimum, and I am only suggesting occasional pushes of the engine and car.

Low revs can be good for fuel economy (after the engine has been fully warmed for a while) but good full economy also comes from some acceleration to nip through the gears to get into higher gears The engine, transmission and other components on the car benefit from being exercised to higher levels occasionally.