420A P0300 repetitve

[ECLIPSEGS2]

1999 Eclipse GS 420a. Constantly popping p0300. When using scan tool to check freeze frames however is shows no PID values and everything show default vehicle off values. What could cause 4 repetitve codes (p0300) to have that happen. And it only happens when the vehicle is at full operating temperatures.

 

[waltah]

Misfires can be caused by anything that upsets fuel/air mixture or by an ignition problem. Consider air leaks (PCV valve been checked lately?), EGR valve, failing ignition part.

The car's history may give clues: A high miles car with the problem having come on gradually might be needing a valve grind -- worn exhaust valves would certainly do that. A compression test will tell you.

These 'waste spark' ignition systems often develop cylinder pair problems but the problem may start as random -- just a 'pop' now and then at a stop sign. Spark plug wires may go bad giving intermittent misfires on one or two cylinders that will at first be 'only sometimes.' Get the engine hot enough at night and watch it run in the dark.

There's a few ideas for things to look at. Tell us more and you'll probably get better suggestions.

 

[ECLIPSEGS2]

Misfires can be caused by anything that upsets fuel/air mixture or by an ignition problem. Consider air leaks (PCV valve been checked lately?), EGR valve, failing ignition part.

The car's history may give clues: A high miles car with the problem having come on gradually might be needing a valve grind -- worn exhaust valves would certainly do that. A compression test will tell you.

These 'waste spark' ignition systems often develop cylinder pair problems but the problem may start as random -- just a 'pop' now and then at a stop sign. Spark plug wires may go bad giving intermittent misfires on one or two cylinders that will at first be 'only sometimes.' Get the engine hot enough at night and watch it run in the dark.

There's a few ideas for things to look at. Tell us more and you'll probably get better suggestions.

Misfire is not felt at all, car runs really smooth. Ignition component are all new and have been tested and are all good. CAS and Crank Sensor are new and have also been tested. Compression on all cylinders is 203-210. PCV has been redone with new hosing and clamps and a new valve. EGR was deleted and sealed off then tested for leaks(none found). Wiring harness inspected near old egr area. Repairs made to damaged/burnt wiring. Headgasket is new and replaced. Timing was triple checked. Alternator is fairly new(10000 miles) battery holds around 14.3v when driving. O2S are both new and read 0.175v- 0.9v, upstream cycles properly and reads the Voltage most of th etime as 0.42-0.5v only exception is heavy acceleration, first start up, and decal. Code P0300 only happens at operating temps when holding 2500-3500 rpm but I wouldnt even know it happening if it werent for the CEL flashing. If it is flashing and I pull my foot off the accelerator is stops flashing. If I hold or push slowly it will continously blink until I release it. But there is no loss of power. When I got codes for a lean code(accidentally left vacuum line unhooked) I could see the freeze frame data. However everytime I get the p0300 it doesnt let me see that data as posted above. Which is my concern cause that seems like a loss of communication somewhere. Car has 180000 miles.

 

[DSMPT]

I don't know if this helps you since P030- codes would be caused by many factors. Here is my experience, I had the P030- codes issue on a used Nissan Armada I bought some years back. I inspected and replaced all parts I could guess including vacuum leak, fuel pump, fuel filter, coils, PCV valves, O2 sensors etc etc, but nothing fixed the code. But even after the code came on, the car was running as it should, no power loss at all. And once I cleared the code, normally at least it took some miles driving to come up again. Sometimes 15 miles sometimes 40 miles. So I was struggling with pin-pointing the cause.
Finally I figured out that some of injector plugs were the cause. they looked fine and were still working normally but it got a bad connection only under some circumstances and the injector signal was cut in an instant and came back working quickly, then at that moment the car got the code. The P030- codes have stopped coming up since I fix the injector plugs connection.

 

[waltah]

Misfire is not felt at all, car runs really smooth.

P0300 is 'random misfire.' That is, the Power Control Module thinks misfiring has occurred but it cannot associate it with a specific cylinder. The reason this is reported is that misfires cause excess gasoline vapor to enter the catalytic converter which may either overheat or damage it, thus a concern for emissions.

It appears reading both the 420a and 4g63T writeups for this code that it is reported when the number of crankshaft revolutions varies irregularly by too much as reported by the Crankshaft Position Sensor. The troubleshooting writeup for the 420a lists all the things that could cause a real misfire but if the engine's running smoothly you don't have that. It also lists 'Crankshaft Position Sensor failed' and 'wiring harness and connectors failed.' By way of details it says check the harness between the PCM and the CPS and check that the CPS is installed correctly.

Was the CPS changed after you began having P0300's or before? Might be worth changing that as it's likely that a marginal signal could cause this code. It's also conceivable that this is a PCM failure and perhaps it's worth substituting that if possible.

Other than rechecking those items I'd suggest you get and read the service manual writeup for troubleshooting this condition because it may trigger something else in your thinking.

Good luck with it. These 'stealth' failures can be tough.

 

[ECLIPSEGS2]

P0300 is 'random misfire.' That is, the Power Control Module thinks misfiring has occurred but it cannot associate it with a specific cylinder. The reason this is reported is that misfires cause excess gasoline vapor to enter the catalytic converter which may either overheat or damage it, thus a concern for emissions.

It appears reading both the 420a and 4g63T writeups for this code that it is reported when the number of crankshaft revolutions varies irregularly by too much as reported by the Crankshaft Position Sensor. The troubleshooting writeup for the 420a lists all the things that could cause a real misfire but if the engine's running smoothly you don't have that. It also lists 'Crankshaft Position Sensor failed' and 'wiring harness and connectors failed.' By way of details it says check the harness between the PCM and the CPS and check that the CPS is installed correctly.

Was the CPS changed after you began having P0300's or before? Might be worth changing that as it's likely that a marginal signal could cause this code. It's also conceivable that this is a PCM failure and perhaps it's worth substituting that if possible.

Other than rechecking those items I'd suggest you get and read the service manual writeup for troubleshooting this condition because it may trigger something else in your thinking.

Good luck with it. These 'stealth' failures can be tough.

CPS was replaced after, I believe it is the injectors though and I'll explain on that. Bought set of 4 oe replacement injectors. 3 were bad one was good. Just having the one new one and 3 old ones i took a 60 mile trip and the CEL only flashed 3 times where as before it wouldve been nearly endless. So I believe the injectors are getting heatsoaked and either running to rich or too lean

 

[ECLIPSEGS2]

CPS was replaced after, I believe it is the injectors though and I'll explain on that. Bought set of 4 oe replacement injectors. 3 were bad one was good. Just having the one new one and 3 old ones i took a 60 mile trip and the CEL only flashed 3 times where as before it wouldve been nearly endless. So I believe the injectors are getting heatsoaked and either running to rich or too lean

I'll let you know once I get 3 more good injectors and throw them in how it goes

 

[waltah]

CPS was replaced after, I believe it is the injectors though and I'll explain on that. Bought set of 4 oe replacement injectors. 3 were bad one was good. Just having the one new one and 3 old ones i took a 60 mile trip and the CEL only flashed 3 times where as before it wouldve been nearly endless. So I believe the injectors are getting heatsoaked and either running to rich or too lean

I probably argue with 'Reality' more often than I should but this seems inconsistent with your observation that the engine actually runs smoothly.

Anyway I look forward to hearing the further adventures!