Possible causes of the malfunction:
- decrease in fuel pressure in the fuel system (see "Checking the pressure in the fuel system");
- increase in air filter resistance (see "Replacing the air filter element");
- contamination of injectors (see "Removal, inspection and installation of injectors");
- carbon deposits on spark plugs (see "Diagnosis of engine condition by the appearance of spark plugs");
- coking of the exhaust system or damage to the exhaust gas neutralizer.
Often, a decrease in engine power and unstable idling are caused by a failure of the throttle position sensor installed in the throttle assembly cover...
... contamination of the valve itself (the places where the contaminants are deposited are shown by arrows) or the suction of foreign air through loose connections of hoses connected to the intake pipe. If it is not possible to restore idle speed by cleaning the throttle valve or tightening the hose clamps, contact a specialist to check the throttle position sensor or replace the throttle assembly. "Removal and installation the throttle assembly").
NOTE: In addition to the listed main reasons, the engine may start poorly and run unsteadily if the purge valve of the adsorber is faulty or if air is sucked in through the connections of the hoses of the fuel vapor recovery system.
If checking all of the above items does not produce results, check the compression in each cylinder (see "Checking the compression in the cylinders"). Normal compression is more than 1.0 MPa, a difference of more than 0.1 MPa in one cylinder indicates the need for engine repair.
[Original version of the article on the website: «ChevyMan.ru»]