Question about 1987 Chevrolet R10

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Code 42 Erratic idle, new iacv, tps set correctly, code 42/mil on now.

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  • Chevrolet Master
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code 42 - a852e451-390b-40d7-a3a9-4d89e8ddd49d.jpg

code 42 is related to EST ... look for the timing connector if plug if not bypass control won't activate and set 42
the pick coil ,ignition module defect ,
hope it helps

Posted on Mar 25, 2014

  • Dave Setnik Apr 01, 2014

    Thanks for your input Denis. I've isolated it now to, as you said, the ign module or dist. pickup. I do not have a gm parts/dealer near me here. So I'm stuck with aftermarket. Any brand/usage suggestions? I was thinking about getting a complete/new performance dist., like MSD. Which I will get a matched coil for as well. I've read too many articles about reliability issues with the cheap reman units.

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shadtremonky
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SOURCE: Code 42 set on an '88 Camaro w TBI.Also very

listen to fuel pump w/ key on , if you hear a spraying sound, you may have a split hose in the tank

Posted on Jun 20, 2009

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2001 mitsubishi galant 2.4 stalling problem


Is check engine light on? If so have scan tool put on it at auto parts store. Get codes and google search the codes. Could be IACV (idle air control valve) or TPS (throttle position sensor) .

Jun 01, 2017 | Mitsubishi Cars & Trucks

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TPS faults and how to fix


1.3b) TPS Throttle Position Sensor faultsSymptoms of faulty TPS:
Associated OBD2 error codes DTCs: P0121 - P0123

  • Poor starting: The engine may start and then stall immediately.The engine may be encouraged to keep running by slowly pressing the accelerator pedal: pressing too quickly may again stall the engine.
  • Erratic/fast idling: The idle may be so erratic as to have some impact on the automatic gear shift characteristics and may actually prevent gear shifts. The engine idle speed may be increased above normal if the TPS fails to report that the throttle is closed. After the engine has been run at high speed the engine may take longer than is usual to return to idle as the ECU will not be able determine how quickly to shorten the injector cycles.
  • Engine hesitancy/ jump in revs: Engine may fail to respond quickly to the accelerator pedal input or may suddenly jump in revs inappropriate to pedal movement. When working properly the TPS should instantaneously signal the rapidly opened throttle position to the ECU. The speed of this signal is much quicker than any similar signal sent from Manifold Air Pressure (MAP) sensor or MAF/IATequivalent. The ECU responds by increasing the fuel injection volumes to match the rapid increase in air volume. If the TPS fails to send the correct signals, the engine will seem to "hesitate" as the throttle is applied as the ECU looks to the other (slower) sensors to determine engine status. A sudden blip of the accelerator at idle can stall the engine (see above - poor start) as the ECU reacts too slowly to increase the injection time to match the sudden intake of air.
  • Engine Misfire: Spurious, beyond normal range, signals from the TPS causes the ECU to set inappropriate fuel injection cycles resulting in misfire.Detected misfire leads to a check engine light(CEL); mal-function indicator lamp (MIL). Cylinders with misfire events detected by the knock sensor may be shut down (disable specific injectors) by the ECU to prevent engine damage.

Note: - With the TPS disconnected the ECU depends on the slower signals it receives from the Mass Air Sensor (MAS) and/or the Manifold Air Pressure (MAP) sensor along with feedback from the oxygen sensor to help regulate engine speed and fuel injection cycle.

How to check? The socket for electrical connection with the TPS has 3 pins, one for 'ground', one for 5 volts 'reference' and a third (generally the middle one) for 'signal' output. Back probe the signal pin in the connector to the TPS. Attach the positive lead of a voltmeter to the probe and measure the voltage output as the throttle plate is rotated. If working correctly the meter should show a voltage consistent with the throttle position from approximately 1 volt when closed and 5 volts when fully open. What is looked for is smooth voltage increase with throttle change.If there are drop outs in the throttle transition voltage signal or if there is no transition then the TPS is faulty.

How to fix? If the track is dirty causing drop outs, try cleaning it with residue-free electrical cleaningspray. If the track is worn it is perhaps easiest toreplace the complete device. In some instances it may be possible to adjust the location of the central mount of the TPS contact arm along the throttle shaft by a few millimeters and in the process cause a fresh concentric region of track to be used

NEXT 1.4) Idle Air/speed control valve

on Jul 15, 2011 | Mercedes-Benz E-Class Cars & Trucks

1 Answer

1998 Mazda Protoge 1.5 L Codes P0120, P0505


It's possible that the EGR passageway is plugged up with carbon, which may facilitate the need to pull the intake off to get it cleaned out properly...You might be able to see if you can run piece of wire into the EGR passageway. TPS and IAC codes could be simply due to them being out of range due to the clogged EGR passage.

Jan 13, 2014 | Mazda Protege Cars & Trucks

1 Answer

Vehicle has a erratic idle . replaced egr valve,tps and idle air control valve . still have the problem.vehicle has the 2.0 litre engine.could not find any vacuum leaks.


Sounds like the engine may have internal wear, whereby the replacement of the egr valve, tps, and iacv won't solve the problem. Perhaps try to do a compression test to find out if the rings and valves are ok. There could also be a problem with a timing chain being worn if so equipped, which affects timing. Sometimes wear inside the engine can throw it out of specifications that the car was originally built to causing an erratic idle on the 2.0L engine.

Nov 04, 2011 | 2003 Mazda Protege

2 Answers

Engine idle speed wont come down under 1700rpm.i have fitted a new speed controller but same problem exists


You are probably having an issue with your IACV idle air control valve located on your throttle body. When the IACV goes out you lose control of your idle. The car may not idle at all or you could find yourself driving down the road at 50 MPH without touching the gas pedal.

Dec 29, 2010 | Mitsubishi Pickup Cars & Trucks

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

Erratic idle


I recently bought a Saturn for my daughter. The car had a hard starting problem (it crank and crank before firing). I got on this site and one possible solution was the temp sensor for the computer. The original unit has a plastic tip that cracks and lets coolant into the electronics. As a temp related problem I would suggest you check or change the temp sensor. At my local Auto Zone the part cost $8.99, so its not an expensive gamble.

Jul 19, 2010 | 1999 Saturn SL

1 Answer

Idle drops at light... Car runs and drives fine, but when stopped in park or drive idle will drop and then come back up it does this once every minute... Has died once (2.0 motor)


sounds like it could be the IACV or possibly the TPS does it have a check engine light if so get the codes read at a parts house like auto zone of advance auto parts. if it is the IACV they get plugged with carbon somtimes and u can clean them with carburetor cleaner or an electrical cleaner.

Oct 21, 2009 | 2000 Nissan Sentra

1 Answer

Surge. loss of poert. backfore exhust, intermuttent, iy will also rin like a new csr fro 100 miles at times.


Check map sensor and vacuum hose going to it. Check tps for binding or sticking. Is tps adjusted correctly? What are the codes? This car has an on-board diagnostic center that you can check all of this while sitting in the car. Fuel pressure should be 9 to12 psi. according to service manual and you need to hook it to a gage for that. . Check timing, it is a certain procedure to set timing on this car that involves going to a "set timing mode" on the diagnostic panel and crossing some connectors. You can also set the tps with diagnostic panel readout. Check for water in fuel system. Check egr ports and vacuum supply, to egr valve also egr solonoid.

May 20, 2009 | 1989 Cadillac Eldorado

5 Answers

300zx engine idle


The reason it's stalling out is because of the adjustments you made to the CAS and TPS. You need to reset the CAS where it was, since when you rotate this sensor, you change the ignition timing. As for the TPS, that also needs to be reset to how it was. The way to adjust the idle on this engine is with a screw on the idle air control valve (IACV). At the back corner of the engine, on top on the driver's side, the IACV is bolted on. If you crouch down next to the driver's fender and look straight in at the IACV (with a flashlight) you will see a screw recessed in there, with the head pointing toward you. That's the idle adjustment screw. With the engine running, AFTER you have reset the CAS and TPS, turn this screw until you are able to set a warm-engine idle of roughly 750 RPM. Messing with TPS voltage and ignition timing is a sure-fire way to stall or blow up your engine.

Oct 18, 2008 | 1990 Nissan 300ZX

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