Engine at times not running smoothly. jerking at times when riding. smokes when revved. car beiing serviced on regular basis and really had a good run . replaced all filters but no luck. beiing advised to replace injecters and pump. sounds very costly.

The best way to solve the problem on your own easily is to get help from service and repair manual with pictures and diagram which guide you to locate and fix the problem and you will get the manual from the given link http://toolsnyou.com/

Check your transmission fluid. Usually if your rig starts shifting hard ( big Jerking motion) it's a sign that your transmission is terminal and the ring is going between the gears

If it has been regularly serviced and tuned up It sounds that it could be a TPS...( Throttle Position Sensor )...or perhaps an 02 sensor...Oxygen sensor...Idle Air Control valve will keep the idle up until vehicle gets warm then it brings the idle down..there are a few things that could cause this....However If any of these are at fault they should flash a trouble code...I have seen times when no code flashed ...Your type vehicle is special....I would check for recalls......In fact don't waste time trying to repair it without trouble codes...Take it to a dealer.

I seem to be answering a bunch of your questions today. Really hope they are helping in some way. White smoke can be lots of things. I little white smoke on a cool morning or a cold day when you first start the car is completely normal. Its just condensation inside the exhaust and cylinders themselves burning off. Lots of white smoke or smoking on a continual basis is not normal...and bad. Usually white smoke on a hot day, or white smoke after more than a few minutes of running the engine is a sign of coolant burn off. Most common causes there are either a warped or cracked head, or a bad head gasket. Again, hope that helps. I do hope all of these questions are in regards to a single car...if they are...it really might be time to consider either an engine swap or giving it up to the scrap yard...blue smoke AND white smoke add up to big problems. Both at the same time out of the same engine on a regular basis, really sounds like a cracked head in my opinion. Either way, good luck man!

any check engine light on>?

You have to find the reason the check engine light is on. This will aid in diagnostics. Also, are you buying fuel at the same place both times?

The Effects of Over Revving a motor can be Catastrophic. I do not understand why the government would require someone to do such a test. Normal Emissions Testing is done at High (2100 - 2500) and the Idle (500-900).

Reason for Increased Smoke.... As you increase the internal pressure of the vehicle, you are creating a VACUUM and this is suckking the Oil past the rings, and anywhere else that it is causing the Vacuum.

Efffects of Over Revving van be Premature Failure of the engine (Could cost you $5-$8,000 to replace)... I would ask WHY so high... A Diesel would MAX OUT their RPM @ 4,000.

These people who are doing the test, ask them to show you where it says in WRITING 4,000... That is much higher than in the 4 states I have been certified to be an I/M Inspector

You need to have the electronic engine control system scanned for fault codes, that is the very 1st step in diagnosis of this problem.

You should have this problem scanned as soon as possible. Usually when the engine light comes on, it means you have a problem But if it blinks its a warning that u should pull over and shut it off to prevent damage to your engine & its parts. It sounds like a fuel injection/emissions problem. I ignored this problem once & it melted my catalytic converters!

check brakes tires steering , check if engine smokes after sitting for awhile just when u start it , check all lites heater radio power windows check if oil is clean drive it and see if tranny shifts in all gears