Eclipse GS Rough Idle / High HC

[Crapter]

1996 Eclipse GS with a rough idle, sits around 1500 and will drop and rise a few hundred rpm as i sit. If i turn on the AC it begins to rise and drop to near 2000, and 1000 rpm also causes the check engine light to flash on. heater doesn't work as well.

runs fine as i drive, tho the AC puts a strain on the power supply so i usually just leave it off, also due to the temporary check engine light it makes pop up which goes away after a few moments.

Would this be caused by my IAC? any feedback would be helpful.

Also i was having some trouble with HC, my first smog put me at 109, after replacing spark plugs, spark plug wires, oil, and oil filter it came out to about 63, so i was just short of passing here in CA. Could the idle problem be affecting the HC in any way?
Also would running a higher octane gas such as a premium with a fuel injector cleaner for the next smog give me enough to pass possibly?

anyways any feedback would be awesome!

 

[hondo0975]

First off before you do anything else do a boost leak test. There could be more than a few things that could cause this however most of the time when it just appears out of the blue it's a vacuum leak. If you can do the boost leak test great if not atleast check for cracked, worn out vacuum lines. You can do a search on here as to how to make a home made boost leak test gage for less then $25.00. Or if you find most of your vacuum line are worn out you can also go to Napa an get several feet of vacuum line an replace them all. If you replace them all just replace one at a time. Remove one line at at time, measure it out with the new line, cut to fit, an replace. Then move to the next line. Hope this helps.

 

[Dert]

His car is N/A so it will never be under boost....OP, have you checked your fuel filter? Could be numerous factors, dirty fuel filter, dirty air filter, cracked vacuum lines, incorrectly gapped or faulty spark plugs, bad plug wires, bad gas, crud in the tank, dirty injectors, start with basics then work up to testing iac, TPS and what not.

 

[hondo0975]

Sorry my bad guess I should have paid more attention.

 

[Slugger865]

Just went through this same thing with the idle. Changed the iac and the problem was solved! You can get them at autozone for $70 but I got mine on eBay for $20.

 

[hondo0975]

Would like to hear if you got you car fixed an if so, what was the problem? If you don't mind?

 

[93AWDDSM]

Sorry my bad guess I should have paid more attention.

if trying to pass HC I would run it hot and hard for a few minutes, Did with the TSi and she passed emissions with no cat

WHAT CAUSES HIGH HYDROCARBON (HC)?

Below are common failures which are likely to produce high Hydrocarbon HC. Hydrocarbons are basically raw fuel, otherwise known as Gasoline. High Hydrocarbon (HC) emissions are almost always a sign of poor fuel ignition. However, it's not always that the engine's ignition system is responsible for high Hydrocarbon emissions. Read on.
1. Improper Ignition Timing - Engine ignition timing is measured in degrees before or after Top Dead Center (TDC). Example of an ignition timing failure would be in the case where an engine's ignition timing is required to be set at 10 degrees Before Top Dead Center (BTDC) and instead is set to 15 degrees BTDC. This fault will not only cause a smog check "functional failure", but will increase Hyrdocarbon (HC) emissions as well. California allows 3 degrees +/- off of the manufacturer's required setting. Note: Late model vehicle's may not have a distributor, and therefore no timing adjustment will be needed. On these engines timing is electronically controlled by the ECU (Engine Control Unit).

2. Defective Ignition Components Your vehicle's ignition system consists of the ignition coil/s, distributor*, distributor cap*, distributor rotor*, ignition wires, and spark plugs. If any of these components are defective the engine will produce high hydrocarbons. A common reason ignition components perform poorly is due to carbon build-up. High ignition voltage traveling through the air pockets within these components form carbon. Carbon acts as an insulator between paths of electricity, decreasing the energy required at the spark plug to ignite the air/fuel in the combustion chambers properly. *Distributor-less engines do not have these components.

3. Lean Fuel Mixture - Any condition which will cause unmetered air to enter the intake manifold, and ultimately the combustion chambers, will cause high hydrocarbons (HC). This condition is called a lean miss-fire. Such faults as vacuum leaks and gasket leaks will cause lean fuel/air mixtures. Broken, disconnected or misrouted vacuum hoses will do the same. It is also important to note that many engine components rely on engine vacuum for proper operation. If any of these components are defective, externally or internally, they may cause large vacuum leaks as well. A good example of such a component is your vehicle's power brake booster.

His car is N/A so it will never be under boost....OP, have you checked your fuel filter? Could be numerous factors, dirty fuel filter, dirty air filter, cracked vacuum lines, incorrectly gapped or faulty spark plugs, bad plug wires, bad gas, crud in the tank, dirty injectors, start with basics then work up to testing iac, TPS and what not.