Mechanics

ENGINE BUCKS, KICKS BACK, STALLS WHEN WARM AFTER STOPPING

Chevrolet Corsica

Electrical problem
1994 Chevy Corsica 6 cyl Two Wheel Drive Automatic 200220 miles

If lucky enough to get back up to speed, OK again until next stop light. Stop at a store, will not start until cooled down. When trying to restart warm, back kick will actually stop the starter rotation momentarily, and puff of smoke will shoot out somewhere over the intake manifold. Service engine light not on. Replaced cam position sensor, no joy. Disconnected knock sensor, car ran fine for a while again until hot, same problem. Something is getting heat sensitive and keeping the spark advanced for cruising speeds at idle/start? Does TPS advance spark? Shop manual shows " ignition timer sensor" but parts stores don't show it. I can swap out my ICM with my 2002 Buick Century (same Part # !) But I don't think that is it.
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Sampojoe
April 25, 2009.



Try the crank sensor, Saturns had trouble like this, and they are a GM product too.

Merlin2021
Apr 26, 2009.
Wow, focused in on the cam sensor, thought that it must be the same thing as a crank sensor.

Thanx

Looks like another tough job to get at, going to see if I drop the skirts if that exposes the sensor, sure hope so, Otherwise, will I have to drop the engine, remove the engine mount (again)?

Tiny
Sampojoe
Apr 26, 2009.
HARD START Symptom Definition Engine cranks okay, but does not start for a long time. Engine eventually starts, and may die immediately or run okay. Possible Cause & Correction Check the following items: Check fuel pump relay by connecting test light between fuel pump relay connector ignition feed circuit and ground. Turn ignition on. Light should illuminate for 2 seconds. If light does not illuminate for 2 seconds, see FUEL PUMP RELAY under FUEL SYSTEM in appropriate I - SYS/COMP TESTS article in the ENGINE PERFORMANCE section below. For location of fuel pump test connector, see COMPONENT LOCATIONS in appropriate I - SYS/COMP TESTS article in the ENGINE PERFORMANCE section. Check for blown injector fuse. • SYSTEM/COMPONENT TESTS - 2.2L • SYSTEM/COMPONENT TESTS - 2.3L • SYSTEM/COMPONENT TESTS - 3.1L • Check for poor quality or water contaminated fuel. • Ensure TP sensor is not sticking or binding. • Check EGR operation. • Check for a leaking injector. To do this on TBI systems, disconnect injector electrical connector at injector. Crank engine and watch for fuel leakage. • Ensure resistance of coolant sensor circuit or coolant sensor is within specification. See SENSOR RANGE CHARTS article in the ENGINE PERFORMANCE section. • Check ignition system for a worn distributor shaft, bare or shorted wires, incorrect pick-up coil resistance, loose ignition coil ground or moisture in distributor cap. Check for adequate spark using Spark Tester (ST-125). • Check for shorts by spraying plug wires with a fine mist of water. • Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits. • Check for correct fuel pressure in all speed ranges. • Check for faulty in-tank fuel pump check valve (MFI only). A faulty in-tank fuel pump check valve will allow fuel in lines to drain back to tank after engine is stopped. To check this condition, turn ignition off, disconnect fuel pressure line at fuel rail and remove filler cap. Connect a radiator test pump and apply 15 psi (1.0 kg/cm 2 ) pressure. If pressure will hold for 60 seconds, check valve is okay. • Ensure the installed PROM is correct for that particular vehicle. Check with dealer for latest application information. • Check for restricted exhaust system. • Check Idle Air Control (IAC) system. Check for vacuum leak at high idle. Check for binding of throttle blade or linkage. Check for water contaminated fuel, correct fuel pressure or a restricted • injector. Check for foreign material in IAC bore of throttle body. Check for proper connection of IAC valve electrical connector. Check for faulty crankcase ventilation valve. Check for failure of A/C compressor or relay. Check MAP or MAF sensor. Check for flooding. • Inspect crankshaft sensor clearance and resistance. Check harmonic balancer interrupter rings for bent or missing vanes. •
Crankshaft Position Sensor A malfunction in the crankshaft position sensor circuit will set a related diagnostic trouble code. For testing procedures, see the TESTS W/CODES - 3.1L article in this section. To diagnose position crankshaft sensor, the following procedures can be used: If a scan tester is available, scan RPM parameter while cranking engine. If RPM is indicated, crankshaft position sensor is operating properly. 1. If scan tester is not available, disconnect crankshaft position sensor harness connector. Set ohmmeter to 2-k/ohm position, and measure resistance across sensor terminals. On 3.1L engines, resistance should be 800-1200 ohms. 2. Set voltmeter on the 2-volt AC scale. Crank engine and measure output voltage across sensor terminals. Voltmeter reading should be .8-1.4 volts. If resistance reading is not as specified or sensor does not produce the specified output voltage reading, repair faulty wiring or faulty crankshaft position sensor. 3.


http://www.2carpros.com/forum/automotive_pictures/62217_Corsica_CKP_1.jpg


Merlin2021
Apr 27, 2009.
Well I've replaced 2 cheap sensors, still have the problem maybe getting worse fast. Rushed, should have at least used a VOM on crank sensor like you suggested. I was so sure they were just becoming heat sensitive. Had a wierd situation since, car sitting in hot sun. On cold start, started rough, would not run. Something just getting a little warm from road/sun on hood/or PCM in cabin? (Windows closed, very hot). Guess I had better swap out my ICM with my buick. Last try then to the shop.

Won't idle in warmer wx for more than 5m after cold start, eng temp only half way to operating range. The way it bucks & coughs, especially on restart attempts, I can't help thinking its spark is advanced too much for low rpm.

Tiny
Sampojoe
Apr 29, 2009.
Test the ECT(engine coolant temperature) and IAT(Intake air temperature) Sensors, with a cold engine the readings should be the same! Very high with an ohm meter 100,000 or so, and the ECT will drop to 177 at operating temps. Of course ignition mods have been known to get sensitive too.

Merlin2021
Apr 29, 2009.
BINGO! ICM swapped out using my buick, runs great, no sign of stalling. Shoulda tried it first!

Tiny
Sampojoe
Apr 29, 2009.
Good work!

Merlin2021
Apr 30, 2009.
The Buick is my wife's car, if I broke it I would be toast!

Boy, that cost me a days labor. I did it once before but I had to have strong motivation to take another chance. But Hey its really easy after all.

Tiny
Sampojoe
May 29, 2009.