Question about 1992 Jeep Wrangler

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1992 jeep 2.5 liter idles high. between 1500-2000 rpm. Changed the idle control valve, drove at 40 mph to reset the ECM, unhooked the batery to reset codes

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Start by verifying that there is no vacuum leak. On a vehicle that is 18yr old I would expect to seek cracked, broken or soft vacuum lines. Also check gaskets for vacuum leaks, especially along intake manifold and the throttle body gasket. A quick, effective and relatively safe (barring sheer idiocy) method is to use quick, short blasts of Berryman's B12 carb cleaner along suspect areas. A vacuum leak will be detected by a change in rpm. But, as with anything else - be careful and use at your own risk!

If you find this solution helpful, then please take a moment to rate it. - Thanks.

Posted on Jun 03, 2010

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Why does it have incorrect idle and hangs on fast idle before dropping down to normal?


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Aug 07, 2015 | Lincoln Navigator Cars & Trucks

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I hooked my 95 Mazda mil up and says I need O2 sensor for bank 1 and 2 and also says I need engine speed circuit not sure wat to replace and wats really messd up please help


First is all always write down the codes you have present, it helps in closing down on the problem. I am assuming you have a 95 Mazda Milleinia

1. Start and run the engine and monitor the oxygen sensor signals and see if this sensor has bad readings still. Check for an open or shorted wire between the sensor and the Engine Control Module (ECM) if the signal is dropping out.

2. Listen for an exhaust leak in the area of the oxygen sensor, the leak could allow oxygen in to the exhaust and skew the sensor readings.

3. Inspect the ECM and ECM connector for signs of something that has been spilled on the ECM. Is the engine idling too high or too low then check this:-
1. Unplug the idle air control valve and turn the air bypass screw in to see if it will idle down. If it will idle down, adjust the idle speed to around 500 RPM's and then plug the idle air control valve back in.

2. If it still idles high, remove the air boot from the throttle body, block the air bypass ports with duct tape, hook the air boot back on and start it. This should make it not idle at all or just barley idle. If it does, the problem is in the idle air control valve.

3. If blocking the air ports doesn't cause it to idle down, the throttle plate must be sticking open. Clean the throttle plate really good and back the throttle stop screw off and then see if it idles down.

4. Verify the coolant level is not low and that coolant is circulating through the idle air control valve. Tech Tips: This idle air control valve is two valves in one. It is a fast idle thermo valve on one side and a duty cycle idle air control valve on the other.

Mar 30, 2015 | 1995 Mazda Millenia

1 Answer

2005 Dodge Ram 1500 4.7 Engine. Starts fine, Idles fine, but when engine shifts into high gear and RPM lowers engine runs really rough under load


Have you checked for a broken valve spring. Repaired a dodge engine with the same running issue as you have described and it was a broken intake valve spring.

Feb 22, 2015 | 2005 Dodge Ram 1500

1 Answer

I have 1990 ford f150 5.8 liter it idles high when in park and idles about 1200 rpm when in gear and sometimes surges up and down. i have clean the idle control and check showing 12.5 ohms still won&#


One common problem is a vac leak or a sticking throttle plate.
The computer controls idle speed by how much air is allowed into the intake. The idle control valve could be sticking even tho you have cleaned it, or have a faulty motor.

Sep 12, 2012 | 1990 Ford F150

1 Answer

The fuel pump was changed,now it idles high.


The idle speed is controlled by an Engine Control Module (ECM).
It needs to be put on a computor to be checked.
The idle air valve provides the control for constant idle speed. In order to set the correct air valve opening to achieve constant idle speed, the fuel injection control unit uses information from the air mass meter, A/C switch, throttle valve switch and the ignition control unit (RPM signal) to regulate the output current to idle air valve. This means, there is alot of things that can make the idle speed go up or down...Hope this was some help to you??

Jul 21, 2011 | 1990 Volvo 740

2 Answers

Idle fluxuates up and down consistantly


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.

Sep 15, 2010 | 1991 Honda Civic

1 Answer

ECM switches from closed loop to open loop at idle after warmup


WHEN ENGINE GOES CLOSED LOOP TO OPEN LOOP.YOU HAVE A RICH FUEL MIXTURE.YOU HAVE A VACUUM LEAK.BY YOU HAVING ROUGH IDLING.AND A HIGH MILEAGE ENGINE I WOULD DO A COMPRESSION TEST OR CYLINDER LEAK DOWN. CHECK FOR LEAKING VALVES AND LOW COMPRESSION .THEY BOTH WILL CAUSE ENGINE TO IDLE ROUGH CAUSE MISFIRE.CAUSE OPEN LOOP CONTAMINATE HO2 SENSOR CAUSE A RICH FUEL MIXTURE.

Sep 30, 2009 | 1984 Oldsmobile Delta 88

2 Answers

Hyundai Sonata 2002 idle at high RPM and accelerate 40-45 MPH


Look for a vacuum leak somewhere. This is the most common problem for a high idle.

Jun 23, 2009 | 2001 Hyundai Accent

2 Answers

Having problems with fuel delivery seems to stall out at idle after it has been running awhile, i have changed fuel filter and spark plugs. 1994 jeep grand cherokee laredo with 318 v8 engine.


go to an electronics shop supplier and get a can of freeze spray.
it cools to -60f. let the jeep run until it misbehaves ,then cool down the ignition module.if it runs,you know it is bad. you could have either a heat related electronic issue,or something like a frozen egr valve ,or iac motor that keeps leaning and leaning out the mixture.
the catalytic converter could be plugged...usually a sulfur smell is with that and setoff the check engine light.
,the computer controls the idle and the fuel injection.
you may have an issue in the ecm itself. cooling down the ecm will let you know if there is an issue.
even a distributor cap that is cracked can heat up and fail
and the lead wires themselves.

May 07, 2009 | 1994 Jeep Grand Cherokee

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