Without knowing more is hard to say. Some things to check though would be injectors if it is fuel injected and the throttle position sensor. If carbuerated may just need adjustment. Best thing to do is spend approx $20 and get the "Chilton's Manual" for your specific vehicle, it contains excellent troubleshooting tips and flowcharts.
This car is computer controlled, and assuming it has the Chevy 305 it is also fuel injected. There is probably a problem in the computer controls causing it not to idle. Do not attempt to adjust idle, as it will not fix it, and may cause other issues when the innitial problem is diagnosed and repaired.
Before you can fix the idle problem on your Vauxhall Frontera, you need to find out the cause of the problem. If the problem is with the fuel pump or fuel filter, they would need to be replaced.
The idle is automatic. If the speed is not corect then you have to fix the problem with the idle motor.
trying to fix simular problem
You will need to replace the intake gaskets to fix your problem. The HEAD GASKETS will not be your problem.
I have the same problem with my 03. I havent figured out the check engine light but take it to a dealer and they will fix the idle problem. they know about it and if you take it to them they'll fix it for free. it has something to do with the computer needing to be cleaned out.
To fix high idle problem on a 1996 VS Commodore, first locate the idle air control valve. Unscrew and unplug electrical connector running to the valve. Turn the valve over and clean the sensor for debris.
The Sputtering tends to be a old or clogged fuel filter the engine is getting starved of fuel replace that and it should fix the problem
First you have to diagnose what the problem is before you can fix it.
buy a can-am and it will fix the problem
fix vapor lock on 1998 chevy s10 2.2 liter 4 cylinder
Correct the idle by adjusting the idle screw on the throttle body if all else fails replace the idle control module located upper center of firewall usually. Hope this helps