WHEN IDLEING VEHICLE MISFIRES AND A TOK TOK SOUND CAN BE HEARD...IF THE REVS PICK UP TO ABOUT30000RPOM THERE ARE NO MISFIRE AND NO TOK TOK SOUND (opel corsa utility 1400 20000 model!

The 20mph could be the vehicle going into a 'Safe' setting also known as 'Limp Home Mode'. It is the vehicle restricting the vehicles performance to prevent further damage and so you can get it, (Slowly!), to a garage.
I'll need more information to help you. Misfires can be a pain in the Tailbone to find as they could be anything from a bad spark plug to a faulty fuel part or one of the engine sensors.
The noises you are hearing could be a clue. What sort of 'Loud Sounds' are they? Is the sound a Banging noise? Grinding? Squealing? 'Clonking? When EXACTLY do you get the "Loud Sounds"?
The coil pack could be faulty and not supplying power. to the spark plug. A misfire could also be a fuel supply issue. You might have a faulty fuel injector or a bad fuel pump.
Use the 'Comment' button below and i'll see what other help I can give you.

Engine revs to attempt to prevent stalling from misfire. Why not just fix misfire and be done?

P0352 - Ignition Coil B Primary/Secondary Circuit Malfunction

do a compression test

Hi Herman, Your problem can have many reasons for misfiring. If the misfire has a regular beat it will most likely be caused by defective plugs, plug leads or a defective coil. (Located on top of each plug.) If the misfire is irregular, it could be a defective crankshaft pick up sensor or camshaft pick up sensor. The problem could also be related to the air flow sensor. Your best course of action is to take the vehicle for a diagnostic scan and thereby pin point the problem. Ask the technician to also carry out a fuel pump pressure test and request a new fuel filter be fitted. Your problem is typical of a vehicle that is not serviced on a regular basis. If that sounds as if I'm telling you off so be it. If you look after a vehicle it will give you good service, if not, be prepared for un scheduled roadside pick-nicks. Did you carry the basket with you today? regards John

it is possible that you have access carbon buildup around your valves or on top of the Pistons that gets hot and on cruise causes the engine to misfire.It is also possible that you have some water in the mix that is forced through under normal conditions that under cruise conditions is causing problems also.

For engine misfiring problem check the help links mentioned below. Click the link below to go through the troubleshooting procedure :---- Engine misses and truck jumps? Hard to down shift? Issue with high gear only? http://technoanswers.blogspot.in/2012/02/engine-miss-and-truck-jumps-hard-to.html

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Bad miss at idle?

http://technoanswers.blogspot.com/2012/01/bad-miss-at-idle.html

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While stop engine idles like cylinder missing?

http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html

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Engine Misfire codes for car?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html
Engine Misfire codes?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html

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Misfire on cylinder 4?

http://schematicsdiagram.blogspot.com/2011/12/misfire-on-cylinder-4.html

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Oil on spark plugs and car misfires?

http://technoanswers.blogspot.in/2012/02/oil-on-spark-plugs-and-car-misfires.html

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This will help.

Thanks.

PO 300 is multiple misfires detected
PO 301, 304, 305, 306 are misfires in cylinders 1,4,5,&6
PO 053 is HO2S Bank 1 Sensor 1 Heater Resistance
PO 106 is MAP/BARO CKT Range / Perf
PO 316 is Misfire detected 1st 1000 Revs.

On a misfire, I usually push towards the spark plugs, plug wires, and coil packs / distributor coil.
You have PO 106 and PO 053 that need to be inquired about at nearest AutoZone.
They can give you an idea as to what is the problem on these.

Did a MAP sensor **** out and cause all the misfires ?
Did a misfire cause the MAP sensor error?
You see what I'm saying ?...Something caused all the misfires...thinking MAP...but not that familiar with the function of the MAP.

Hope this helps...

The ignition modulator may have to be replaced, you can pick one up at Auto Zone and it's still pretty expensive so you may want to try the Salvage yards. The ignition modulator's are common interchangeable part for the GM line so you can get one from a newer car then your 89 cavalier. Good luck and hope this helps. I believe Auto Zone can also test the ignition modulator too, the modulator is what the coils sit on. 

Have you tried moving the spark plug and/or lead to another cylinder to see if the misfire moves? If it doesn't change, i.e. No. 3 cylinder still misfires i'd carry out a compression or cylinder leak test.