I drove to Chicago today. 150 some miles without trouble. 2 miles from my destination I get misfires.
I found an AZ and had a code P1351 - Ignition Coil Control Circuit High Voltage. Replaced the coil,disconnected the battery, and cleared the codes. Engine seemed to run better for a few minutes. SES light came back on.
I know have a P0300, muliple misfires. Got any ideas?

 

[&o] Here's the flow chart for your P1351, looks like it is probably the ICM, but could be caused by the PCM or the wiring between them. Keep us posted and let me know if I can help.

DTC P1351 Ignition Coil Control Circuit High Voltage

[IMG]local://upfiles/3319/84661B837DD04A31868D43E1F6E576A6.gif[/IMG]

Circuit Description
The enhanced ignition system uses the crankshaft position (CKP) sensor in order to provide a timing input to the control module. Ignition control (IC) spark timing for each cylinder is based on this input. The control module provides the ignition timing signal to the ignition control module (ICM) to control the ignition coil. Each timing pulse detected by the ICM allows it to energize the ignition coil. A large secondary ignition voltage is induced in the secondary coil by the primary coil. This high voltage is switched to the correct spark plug by the distributor.
This DTC will set if the VCM detects an unusually high voltage on the ignition timing signal circuit.
Conditions for Running the DTC[*]The ignition control is enabled.[*]The engine speed is less than 250RPM.
Conditions for Setting the DTC
The ignition control voltage is more than 4.9volts.
Action Taken When the DTC Sets[*]The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2consecutive key cycles.[*]The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records.
Conditions for Clearing the MIL or DTC[*]The control module turns OFF the MIL after 3consecutive drive trips when the test has run and passed.[*]A history DTC will clear if no fault conditions have been detected for 40warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C(40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C(158°F) during the same ignition cycle.[*]Use a scan tool in order to clear the DTCs.
Diagnostic Aids
Intermittent test -- If the connections and the harness check OK, monitor a DMM connected between VCM terminal C3 pin 9 and C4 pin 18 while moving related connectors and wiring harness. If the failure is induced, the voltage reading will change. This may help to isolate the location of the malfunction.
An intermittent may be caused by any of the following conditions:[*]A poor connection[*]Rubbed through wire insulation[*]A broken wire inside the insulation
Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table. [ol]

This step determines if the DTC is an intermittent.

This step checks if the IC signal from the VCM is available at the ignition control module.[/ol]





Step

Action

Values

Yes

No


1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check


2 [ol]Clear the

 

Thanks LastCoupe.
I'll pull the ICM in the morning and have AZ test it.

 

I am no longer getting the P1351 code, now I just get a P0300-Multiple random misfires. She idles like crap, revs up fine for the most part. Hesitates when you vback off the peddle. runs like crap anytime under load. Idle is the worst, and has died.

I have replaced the coil, spark plugs, and plug wires. I had the ICM tested and it tested out Good, they ran the test about 20 times in a row. Plugs and wires had about 50,000miles so I figured they were due anyway. Plus I had Bosch plugs in there, now I have the AC Delcos.

I added 16 galons of fresh gas to my 18 gallon tank, no difference.

Sprayed ether around the engine compartment hoping it might lead me to a vacuum leak.Nope.
Sprayed water on the distriburator cap, hoping to find a crack. Nope. Contacts in the cap and rotor looked pretty good, alittle carbon fouling. I cleaned them off.

I dont have a fuel pressure tester.
I called the dealer today, and a diagostic test is about $43-$86. I am thinking this is the way to go. Would be cheaper in the long run to have them hook it up to their equipment and diagnosethe problem. I could throw parts at it all day long and never fix the problem.

Web searches yeild anything from electrical, ignition, fuel, and vacuum. That $86 bucks is sounding pretty cheap especially when you figure I could spend all day with a multimeter and never find the problem.

Looking for any tips, or things to ask, mention to the dealer?
Are there any condtions the test equipment wont diagnose?
This time I am going to be a parts changer and leave the diagnosistics to the pros.

 

Probably wise to have the dealer hook up the tech 2 and see which cylinders are missing...they can look at live misfire data and see exactly which one (or more) is not firing properly. If it is on all cylinders you could have a bad new coil, crank sensor, pickup coil, fuel pressure regulator leakingor PCM. If it's only one or 2 it's more than likely injectors.

 

I definitely agree with lastcoupe.

If it ends up being the FPR or injectors, you may want to look at the updated MFI injection spider which is a direct drop in replacement for the SCFI spider. And, depending on your source for single injectors, it may be cheaper in the long run to just replace the whole thing. I posted the PN awhile back.

 

Hanr3[/align]Some information here to look at and go over, These are someCOMMON P0300 problems in our 4.3's......
Good Luck
Dino...


Injector poppets clog after engine work
Engine is misfiring, possibly on multiple cylinders. Symptoms appear after engine work such as intake or head gasket replacement. In some cases, the engine may not start at all.

Fuel pressure is critical on CSFI systems.
Crank-no-start, low power, surging, rough idle, stalls frequently.
Possible lean codes, possible misfire codes. This tip only applies to vehicles with Central Sequential Fuel Injection (CSFI) or Central Port Injection (CPI, CFI). These systems require high fuel pressures of 55+ depending on year and model. The early '90s 4.3 liter engines needed 55 PSI. Starting in 1996, the 4.3 and the 5.0, 5.7 needed a minimum of 60 PSI to start. Fuel pressure may be slightly lower than 60 while idling, but must be at least 60 PSI to start the engine.

EGR valve sticking open
Possible rough idle and stalling at idle. May set codes P1406, P0404, P1404 EGR Valve Pintle Position Circuit. May also set rich codes or misfire codes such as P0172, P0175, P0300 etc.
NOTE: This tip only applies to vehicles with an electronic EGR valve.

Carbon build-up on injector poppet valves.
Engine misfire, rough idle, possible rich or lean codes. This tip only applies to vehicles with CPI, CSFI, CSI injections systems.

Distributor cap causing misfires and hard start
Engine misfires, especially under a load. In some cases, the engine may fail to start or may kick back while cranking as if timing were off.

Intake gasket internally leaking
Rough idle, misfire codes, lean codes.
Engine runs smoother if the RPMs are raised.

Injector assembly or internal fuel pressure regulator leaking.
The most common symptom is a hard start, long crank after vehicle has been sitting for a short time or over night. Vehicle may run rough for several moments after starting and may have black smoke from tailpipe after start-up. Possible CEL with misfire or rich codes.
NOTE: This tip ONLY applies to vehicles with CPI, CFI, CSFI injection systems.

O2 sensor failures
Engine has a rough idle and misfires. All cylinders on one side of the engine are misfiring. Plugs on one side may be carbon fouled, and other plugs may be ok. May have misfire and/or system lean codes stored. Vehicle may start and idle ok until it goes into closed loop, then begins to run rough.

Light misfire or shudder after injector assembly removal or replacement.
Light misfire, surge, or shudder that may be mistaken as a torque converter shudder. Symptoms appear after the fuel injector assembly has been removed or replaced.

Crank sensor air gap too small
Engine intermittently cuts out or misfires. Possible misfire codes stored. Possible P0335 or P0336 stored.[/align]

 

Thanks.
It starts right up every time. No hard starts.
I only get Code P0300. IT swoud be some much better if I would get another code to go with it. code P0300 pretty much tells me something I already know. Its misfiring.

I suspect an internal fuel leak, however I am going to let the dealer diagnose it, and go from there. I could spent a lot of time trying to diagnose it, and a lot of money thowing parts at it. I dropped it off at the dealer tonight. I'll let you all know tomorrow what I find out.

 

my p0300 was the cam sensor in the distributor. 97 blazer. my problem is solved and the 97 is running better than ever see my post which is current.

 

Try cleaning your EGR. If it is stuck open you would get multiple cylinder misfires.