I need to find the Idle Air Control Valve on a '97 VW jetta

Trouble Code: P0304

Cylinder 4 Misfire Detected

Possible Causes:


Air leak in the intake manifold, or in the EGR or PCV system.Base engine mechanical fault that affects only Cylinder 4.Fuel delivery component fault that affects only Cylinder 4 (i.e., a contaminated, dirty or sticking fuel injector).Ignition system problem (coil or plug) that affects Cylinder 4.Trouble Code: P0505

Idle Air Control, Auxiliary Air Control Valve Circuit Malfunction

Possible Causes:


IACV-AAC valve control circuit is open or shorted to ground.IACV-AAC valve control circuit is shorted to system power (B+).IACV-AAC valve is damaged or has failed.PCM is damaged or has failed.

The problem that you describe is in no way normal. That six second lag that you describe is more than enough time to get you into a serious accident. I have experienced a similar issue on Mitsubishi automobiles. When the hold down on the throttle cable is holding the cable too tight (not enough slack in the cable) or if someone has adjusted the throttle cable to remove the slack causing it to be too tight it will cause a fast idle lag like you describe. On several fuel injected cars stick and automatic I have experienced the engine rev issue you describe. Every time it was fixed by setting the cable tension back too loose.
Another item, if the cable slack does not fix the problem, fuel injected cars are fitted with an Idle Air Control Valve (IACV). They are located on or by the intake throttle valve. The price range for most is $30 to $100. If they malfunction they will raise the idle speed by letting too much air go around the throttle valve raising the engine speed even though the valve is closed. You can check if the throttle cable is too tight yourself. The IACV may have to be checked at the dealer. Only the dealer can tell you if the problem is covered under warranty.
As always check to make sure that there are no loose vacuum lines under the hood.

You probably have a bad Idle Air Control Valve (IACV). If it does not control the idle correctly , you can find yourself driving 50 MPH with out touching the gas pedal. The IACV is located on the throttle control valve and is typically held on by two or three small screws. The price for an IACV can run from $25 to $500. I purchased a throttle body for $40 , removed the IACV, and saved $400.

You probably have a bad Idle Air Control Valve (IACV). In fuel injected carburetors when the throttle valve is closed the IACV opens and closes to control the idle speed. If it malfunctions the engine may rev up allowing the car if in gear to accelerate on its own . When I had a bad IACV in my Mitsubishi Lancer it would drive down the road at 50 mph with out touching the gas pedal. Fortunately, it could be slowed down by using the brakes (unlike the Toyota stories).

Check the Idle Control System

Idle speed is controlled by the Idle Air Control Valve (IACV). The IACV changes the amount of air being bypassed to the intake manifold, in response to electric current controlled by the ECM. When the IACV is activated, the valve opens to maintain proper idle speed.

Symptom and Subsystems to Check:

1. Difficult to start engine, when cold--check Fast Idle Thermo Valve.

2. Fast idle out of spec, when cold:
a. Check Fast Idle Thermo Valve.
b. Check IACV.
c. Check idle adjusting screw (see Section C).

3. Rough idle:
a. Check hoses and connections.
b. Check IACV.

4. RPM too high, when warm:
a. Check IACV.
b. Check Fast Idle Thermo Valve.
c. Check hoses and connections, check Power Steering Pressure Switch Signal, and check idle adjusting screw.

5. RPM too low, when warm:
a. Idle speed is below specified rpm, with no load--check IACV and idle adjusting screw.
b. Idle speed doesn't increase after initial start up--check IACV.
c. Idle speed drops in gear (automatic transmission)--check automatic transaxle gear position switch signal.
d. Idle speed drops when AC is on--check air conditioning signal and IACV.
e. Idle speed drops when steering wheel is turned--check power steering pressure switch signal and IACV.
f. Idle speed fluctuates with electrical load--check hoses and connections, IACV, and Alternator FR Signal.

6. Frequent stalling, while warming up--check IACV and idle adjusting screw.

7. Frequent stalling, after warming up--check idle adjusting screw and IACV.

Additional Steps:

. Check Alternator FR Signal. Have alternator inspected, if idle speed fluctuates with electrical load. The FR signal communicates to the ECM how "hard" the alternator is working to meet the electrical demands of the car, including the battery and any loads which aren't monitored by the ELD. This square-wave signal varies in pulse width, according to the load on the alternator. The ECM places, approximately, 5 reference volts on the wire. The voltage regulator will drop this signal to approximately 1.2 volts, in proportion to alternator load. The ECM compares the electrical load (ELD) signal with the FR (Charging Rate) signal from the alternator and uses that information to set the idle speed and turn the alternator on and off. This helps fuel economy.

. Clean main ECM ground on thermostat housing.

. Reset ECM, by removing the 7.5 amp Back Up Fuse, in the under-hood fuse box, for 10 seconds.

. Replace PCV Valve, cleaning hose with brake cleaner spray.

. Substitute a known-good ECM. If symptom goes away, replace original ECM.

Check the ICM (Erratic RPM and PGM-FI System)

When the engine is cold, the air conditioner compressor is on, the transmission is in gear (automatic transmission only) or the alternator is charging, the ECM controls current to the Idle Air Control (IAC) Valve to maintain correct idle speed. Here's an overview of how the PGM-FI System works.

Background:

Various inputs to the ECM are TDC/CKP/CYP Sensor, MAP Sensor, ECT Sensor, IAT Sensor, TP Sensor, HO2S, VSS, BARO Sensor, EGR Valve Lift Sensor, Starter Signal, Alternator FR Signal, Air Conditioning Signal, Automatic Transmission Shift Position Signal, Battery Voltage (Ignition 1) Brake Switch Signal, PSP Switch Signal, ELD, and VTEC Pressure Switch.

Inputs are received and processed by the ECM's Fuel Injector Timing and Duration, Electronic Idle Control, Other Control Functions, Ignition Timing Control, and ECM Back-up Functions. These are the primary functional areas within the ECM.

Outputs from the ECM control Fuel Injectors, PGM-FI Main Relay (Fuel Pump), MIL (Check Engine Light), Idle Air Control (IAC) Valve, A/C Compressor Clutch Relay, Ignition Control Module (ICM), EVAP Purge Control Solenoid Valve, HO2S Heater, EGR Control Solenoid Valve, Alternator, Lock-up Solenoid Valve A/B (A/T), VTEC Solenoid Valve, and Interlock Control Unit.

Idle RPM:

Once you understand how the PGM-FI system is configured, it's easy to see how the ECM, Idle Air Control Valve, and the Ignition Control Module affect idle rpm. If the ECM's Electronic Idle Control function is not working properly, then it cannot properly control the IAC Valve. Likewise, if the ECM's Ignition Timing Control function is not operating properly, it cannot properly control the ICM (igniter). Obviously, idle rpm will also be affected if there's a problem with the IAC Valve or the ICM. As stated above, the ECM controls current to the Idle Air Control (IAC) Valve to maintain correct idle speed. This cannot happen if the IAC Valve is failing. The same situation exists if the ICM is failing. The ECM will tell the ICM to open and close the primary voltage circuit going to the coil and it won't respond properly. The result will be erratic spark plug firing and erratic rpm.

Conclusion:

If you are experiencing erratic idle rpm, try and isolate whether the problem is caused by the ICM (ignitor), IAC Valve, or the ECM. My experience has been that a failing ICM is usually responsible for the problem. Keep in mind that tachometers are connected directly to the ICM. Therefore, a fluctuating tachometer needle is often a dead giveaway. Heat and poor preventive maintenance (causing high secondary voltage to be discharge on internal distributor components) frequently causes the ICM (and coil) to fail. Besides performance, this is another reason why it's important to regularly replace spark plugs, spark plug wires, rotors, and distributor caps. Electricity will always follow the path of least resistance, even if it isn't the intended one. Our job is to ensure the intended path is the path of least resistance.

Ignitor (ICM) and Coil Replacement:

1. Disconnect negative battery cable.
2. Remove hex head machine screws, securing distributor cap to housing, using an 8 mm nut driver.
3. Move distributor cap and wires off to the side.
4. Remove machine screw securing rotor to shaft, using a #2 Phillips head screwdriver. It may be necessary to "hit" the starter once or twice, in order to rotate rotor for access to mounting screw.
5. Remove rotor and leak cover.
6. Unfasten ignitor wires, remove coil mounting screws, and set coil aside. Note: Removing coil first improves access to igniter.
7. Unfasten screws securing igniter to housing.
8. Remove ignitor from distributor and unfasten screws mounting ignitor to heat sink.
9. Coat back of new ignitor (or old igniter, if reusing) and male connectors with silicone grease. Silicone grease increases heat transfer to heat sink. Failure to apply silicone grease will cause the ignitor to quickly fail.
10. Mount ignitor to heat sink and reinstall ignitor, igniter terminal wires, coil, coil wires, leak cover, rotor, and distributor cap. Ensure female ignitor terminals fit snugly--crimp with pliers, if necessary.

AutoZone can test ICMs and coils for free. If you plan to keep the car, I would replace the ICM due the age of your Civic.

The surging is related to your Idle Air Control Valve (IACV), it adjusts idle based on coolant temperature, your coolant could be low or your IACV could be bad.

bad fuel pump.- just replace it and your good to go!

start witha new fuel filter and perhaps a intank additive such as heat. also look inside the air box for nests. also common. if all is clear, let it run and idle for about 10-15 minutes look underneath the vehicle and look to see if anything under there is cherry red. if not try holding the accelerator down for a few momoents and check again. if it glows, replace the catalytic converter.

sometimes there is a secondary relay on the fender or firewall if there is that needs to be checked to see if it is getting the proper currentif so it more than likely is your sensor