Engine Surging when driving down on motorway and accelerating from a stop.

[therandike]

when driving down the motorway, a sudden surge forward feeling. This used to happen when stopped at the roundabout and accelerating away. Spark plugs were replaced.

This tends to happen when the engine is warm after driving for 40 minutes or so.
It is unlikely the transmission as when driving down at steady sped i felt the surge couple of times.  Could this the coils?
This happen once every 100-125 miles.  So it is hard to diagnose, no codes or engine light. I was wondering if anyone had any tips and helps.
Also there very slight rough idle like skipping heart beat feeling which can be felt while sitting on the driver's seat.

[Lord Voltermore]

You could try putting a dose of  fuel injector cleaner in the tank.  Chose the concentrated type designed to give noticeable results in just one dose  on injectors that are already dirty.   Not the cheaper ones designed to prevent the injectors ever getting dirty in the first place when used in every tankful over a long period. 

If any injectors are not running smoothly or giving a good spray pattern I  believe an excess of petrol can build and the engine runs 'rich'.  But if the excess petrol is 'burned off'  and the engine once again achieves the ideal  14.7 :1 air fuel mix the engine starts to  run better , with a surge. It might even use some of the excess petrol build up like its more throttle input. Rough running at tickover may be in effect be   mini surges.
 
There may be other causes of the surging such as spark plugs, coils, air filter, fuel pressure etc    but I think a dose  of cleaner might be worth a try initially.

[therandike]

Thank you. I will give it go.  I have already replaced spark plugs.

car done 133k miles, so really do not want to put expensive coils. Maybe I can by eco set of coils. This car takes 8 of them.

I am thinking of using Liqui Moly Injection Cleaner

[guest334]

suggest you find the local diagnostic tech the trade use in your area, save time and you will have afull status before spending any £ on parts. If it were mine I would ask what happened immedialty before this fault appeared, what was last changed, swop known good coil to other plugs. Id also vist the local breakers yard check for similar age Jazz check the coils if OE or real Denso get a few and check & replace and necessary. 85% of fault are electrical
Avoid anything advertised as car parts on internet Fleabay and avoid Amazonia land of copy of copied parts.

[therandike]

Nothing was changed. Just started happening.

DO you think at 133k worth putting in OEM parts? it is already started rust under the body. Rear sub frame. I used some treatment for it so that will probably extend the life for another 3 years before MOT failing. 

[PaulCowie]

My Jazz started surging  at around 280 000 km and after changing plugs etc, I finally cleaned the THROTTLE BODY and sorted out the problem.

Not a difficult job and  very clearly explained on YouTube