The car was given to me a short time ago. It's a 1998 Skoda Felicia with a 1.3 Mpi engine.
The problem I am having is that when the car is idling the engine will shake noticeably around every 4 seconds.
As far as I know no maintenance work has been done on the engine and we are planning to change the oil(which is in bad condition) and oil filter.
I don't know the condition of the air filter and I'm not sure it could cause this issue.
The person I work with on the car said that it was probably the water pump chain that has gotten loose and needs to be replaced, or tightened(which I don't think can be done).
I also read around the forums that Valve clearances should be adjusted every 10k miles, which as far as I know hasn't been done yet.
We also had some issues with the car discharging the battery due to leaks and a cable that had the insulation burned out, I isolated it and we will take care of the leak.
So I decided to ask you guys before we embark on a wild goose chase and seeing as the water pump chain is placed in a place that might be tricky to reach, I'd like to hear a second opinion on the problem.

A rough engine idle could mean many things. It is a complex issue. It could be fuel related, spark related, timing related, air related, sensors related or compression related. You need to gather more data by doing some diagnose tests. The rule of thumb is "don't change any part unless you found enough evidence". You gather evidence using your senses first then use testing equipment.

 

You can start in many ways. On cars with a distributor I would start with a cylinder balance test which means locating the cylinder causing a lack of power and not contributing to the engine’s balance and performance. Each cylinder's ignition is disabled at idle and the rpm drop is recorded. Disconnecting the plug boot from its corresponding spark plug or distributor is the most often used method.

 

Sadly on your car you can't do this test easily. So I would go first with a compression test to know the mechanical health of the engine. You didn't tell us the mileage of your car. When you go to a doctor, the first question you get asked is "how old are you?". Then you get questions about your life style and health maintenance. I hope you got the drift.

 

Remember that the more information you share, the easier will be to help you.

The car has around 107800 km driven.
The guy I'm working with said that he suspects the timing chain to be the problem and wants us to change it, because he thinks it wobbles when the engine is running and messes with the opening and closing of the valves, alternatively he wants us to add a tensioner but it looks like the space around the chain is fairly limited so that might not be an option.
I'll try a cylinder balance test too so we can tick that one off the list too.
I read how to do a compression test too, so we might check that one out too if we can find a compression tester.
As for changing or checking the timing chain is it possible to remove the cover of the chain without having to completely demount the engine from the car?

Edited 12 August, 20187 yr by Ascend33

6 hours ago, Ascend33 said:

alternatively he wants us to add a tensioner

Skoda Felicia engine doesn't need it. Not only because there is not enough room for that but because Skoda factory manual says the timing chain should be replaced every 80.000 km.

 

6 hours ago, Ascend33 said:

As for changing or checking the timing chain is it possible to remove the cover of the chain without having to completely demount the engine from the car?

The engine should only be lowered on the timing chain side to get access to all bolts of the cover. No need to remove the engine.

 

6 hours ago, Ascend33 said:

...because he thinks it wobbles when the engine is running and messes with the opening and closing of the valves

Here is a photo of the last timing chain I changed on a client's Felicia at 180.000 (!) km. The engine had good idle but low performance issues. Not to mention the noise...

Great, thank you, you've been a big help.
We might need to find a good chain because I've read from other posts that low quality chains wear out too quickly and cause the same problem down the line.
Thanks again, I will update if we have any progress on the problem

One important tip. Make sure the small hole in the engine block that splashes oil on the chain is free. That is why many timing chains on Felicia and Fabia wear prematurely.

I can confirm that timing chain is not likely cause of bad idle. Chain in my engine have around 120k km, it rattles a lot, but idle is fine. Bad valve clearance was causing more trouble, especially on cold engine. Replacing chain is not neccesary, but it will help with engine noise and performance. Look either for original spare part or part from ČZ chains (OEM manufacturer)

 

It's good idea to change spark plugs. Another cause can be dirty throttle valve or vacuum leakage in intake. These are easiest and worth to check even if engine works fine

Edited 12 August, 20187 yr by Papez
Typos

How about recording a video of the engine running at idle and posting it to see/hear it?