QuestionHi...
I own a 2000 Cavalier and 2 months ago it was idling very hard so I had it looked at. Turns out I was running on 3 cylinders because I lost an ignition wire, so we replaced it and it ran fine. Now it's idling hard again and slowly getting worse. I figured as a quick fix I'd try to change all four plugs and wires myself. Do you think this will help? What else could be causing the hard idling? Could it be timing?
Also, if I'm changing plugs and wires myself, is there anything I need to know to do special. I don't want to screw anything up here.
AnswerHello Neal,
You can replace them, just make sure you run them to the same place. No rocket science, and nothing special.
In addition to that being a possible cause, there are a few more.
Look for any signs of a vacuum leak. Hoses are one area, but two other areas that are often overlooked are the brake booster, and the EGR valve.
The EGR valve opens when directed by the computer, but if a piece of carbon happens to get lodged in the seat when it closes, it becomes a vacuum leak, and has a major effect on idle. It can be easily removed and cleaned, and should be as a regular maintenance item.
Other remote possibilities are the fuel pressure regulator, which has a vacuum diaphragm operated valve in the fuel rail. If it leaks, it not only leaks vacuum, but sucks gas directly into the intake.
If the engine is allowed to run for a long period with poor performance, and black smoke, the catalytic converter can be melted internally, and become restricted, which will cause worse performance, as well as emission problems. Kinda like plugging the tail pipe with a potato.
There are also several sensors that could possibly be bad, such as TPS, O2, Mass Air Flow, etc, but before replacing any expensive parts, check all wire connections, check the air filter for restriction, and check the vacuum system.
Then get a manual, and all of those sensors can be tested before just replacing them.
Good luck,
Van
