P0300 help

[bigblue3643]

just bought a complete stock 98 GST with 118k on it. I randomly get code P0300, the car runs like crap with no power and stutters real bad, this only last a few miles and then it will run fine(still has code P0300) If I clear it sometimes it will stay away for a few hundred miles then it will trip again. anyone have any ideas? also right before this happens usually my tach will go crazy or it will just be dead, nothing else seems to be affected i.e boost., just the performance.

[primo513]

The code is for a cylinder misfire, which could be caused by mulitple different reasons. Have you tried to trouble shoot yet?

[delta448]

Are you trying to use a 1G or 97+ CAS with your 95 ECU?

You might need to make a signal inverter.

[PieEyedPiper]

Multiple Cylinder Misfire P0300
P0300 Random Misfire
[RESOLVED] misfire help P0300 - ISC & coil results
p0300(yes another one(possibly resolved))
p0300 random misfire in all cylinders help!
My P0300 Fix...
HELP Would this (Power Transistor) Cause P0300 Random Misfire Code

Good luck

p.s. there's even more..

[bigblue3643]

I have go e through all of the countless pages about this code. The first night I got the car I put 87 octane in out of habitt, code tripped tach went hay wire and then would run fine. Put 91 octane and the code stayed clear for a whole tank of fuel. Through some 93 in it and it ran worse than the 87. Would that be enough to screw up my plugs. While the car was running I pulled each wire starting with number 1. When I pulled 1 and 4 the car shut off and when 2 and 3 were pulled nothing happened. So I switch the plugs and did it again same result but the car now runs way worse and does not "smooth" out. The wires out of the coils are correct and I have plenty of spark in all cylinders. Anymore ideas??????

And no the car is STOCK with its original engine

[delta448]

The octane rating has nothing to do with it. If the engine knocks, the ECU retards timing.

Pull the plugs and ensure that they are the right ones and are gapped to between 0.024-0.028".

Originally Posted by bigblue3643

So I switch the plugs and did it again same result but the car now runs way worse and does not "smooth" out.

What plugs did you switch out? What ones did you put in and what were they gapped to?

[Artago]

Originally Posted by PieEyedPiper

Multiple Cylinder Misfire P0300
P0300 Random Misfire
[RESOLVED] misfire help P0300 - ISC & coil results
p0300(yes another one(possibly resolved))
p0300 random misfire in all cylinders help!
My P0300 Fix...
HELP Would this (Power Transistor) Cause P0300 Random Misfire Code

Good luck

p.s. there's even more..

Are you still fighting that P0300?

[primo513]

If your spark is fine, have you checked your injectors? ive had plenty of misfiring caused by either clogged or stuck injectors, spent 3 weeks myself trying to figure out that issue on my 1g

[bigblue3643]

Replaced plugs just to be shore. Issue is way worse and now I'm trying to get the car home ASAP be haze it's now overheating like a bastard. What do you mean octane has nothing to do with spark? Your an idiot dude and might want to go get an education

[PieEyedPiper]

Originally Posted by Artago

Are you still fighting that P0300?

Nope!

Originally Posted by bigblue3643

Replaced plugs just to be shore. Issue is way worse and now I'm trying to get the car home ASAP be haze it's now overheating like a bastard. What do you mean octane has nothing to do with spark? Your an idiot dude and might want to go get an education

Oh, goodness.

Well, I'm out of here - that's for sure.
This issue is not related to fuel octane and you ought to heed the advice you've come here seeking.

[bigblue3643]

Used ngk spark plugs bpr6egp gapped to .028
Any ideas on the fact that I can pul the wires off of 1 and 4 and it dies and I pull 2 and 3 and nothing happens

[delta448]

I know you said you have plenty of spark everywhere but if you don't see any change when you pull a wire off of 2 or 3 then you're probably running on only 1 and 4 to start with. Have you checked out your 2 & 3 coil with a DMM?




If you're not producing spark in 2 cylinders, you're pushing unburnt fuel into the exhaust which is a great way to quickly heat things up under the hood.




Please educate me on how the octane rating of your fuel would cause this issue.

[bigblue3643]

Brand new coil packs and I have spark in all 4 cylinders. As far as the octane level affecting spark I was referring to the different flash point of each octane level. If you change your octane level I wass wondering what that does to the ignition system and if it had ties to the code. So yeah still barley running. Has to be injectors? Also on the left side of the valve cover there is a sensor, does anyone know what that is based on my great description.

[stann999]

That is the cam angle sensor. That could also be the problem. It sends the information about timing to the ECU.

[delta448]

Originally Posted by bigblue3643

Also on the left side of the valve cover there is a sensor, does anyone know what that is based on my great description.

That's probably what I was talking about in this post:

Originally Posted by delta448

Are you trying to use a 1G or 97+ CAS with your 95 ECU?

FYI, the stock 95-96 CAS sensor is located on the timing belt side under the intake cam's timing sprocket. If you have a CAS sensor on the passenger side end of the intake cam, you have either a 1G or 97+ CAS. The big difference is that if you're using a 95 ECU, then it expects to see the signal from the 95-96 style CAS. The output from the 95-96 CAS just happens to be inverted compared to the output from all other CAS sensors.

Some 95-96 and ECMLink guys run a 1G CAS without issue, but an incompatible CAS signal is the most common reason I've seen cause the random misfire DTC.

Originally Posted by bigblue3643

As far as the octane level affecting spark I was referring to the different flash point of each octane level. If you change your octane level I wass wondering what that does to the ignition system and if it had ties to the code.

Assuming you properly align the ECU to 5* BTDC base ignition timing with a timing light, the ECU then uses the signals from the CAS and CPS to determine crankshaft angle. That's why it's so important to align an adjustable 1G CAS with the proper base timing before tuning, it aligns the ECU's commanded timing with the physical spark event. Otherwise you can't know what your actual ignition timing advance is.

The ECU looks up the value for spark advance from the high octane ignition table based on the current engine speed and load, and using the base timing alignment as a reference, it fires one of the two coils at the advance angle in that table. Then the ECU listens through the knock sensor to determine if that timing advance caused improper combustion to occur. If it did, the ECU retards the advance angle and uses a value somewhere between the high octane table's value and the low octane table's value.

If it keeps hearing knock it will continue to pull timing until it is operating solely on the low octane table, and it will use the BCS to keep boost from exceeding the wastegate actuator pressure. It is at this point that you might get a misfire DTC, but usually it will specify which cylinders are knocking by setting the codes for those specific cylinders. If you're getting the random misfire code, then there's almost always a mechanical problem. The knock feedback putting you into the low octane table is designed to give a fail-safe limp-home mode and it is overly safe and conservative, even if you did run 87 octane.

[bigblue3643]

Ok I'm confused about the ecu differences 1g 2g and what not. The car is stock with a stock ecu. So here's what I have done:
Plugs
Wires
Coils
Cam p sensor
Tested all injectors
Reset the ecu and made sure the code was cleared. Fired up the car ran normal for about 5 seconds and then ran like shit. My tach is now dead. I took it for a test run and it would barley move, at times it would run great for a second or two then run like shit. The tach was dead the whole time. Before this problem got worse the tach would do some crazy rotations at any rpm. While the car is idling ( when it want to) I pulled the wires one at a time to try to narrow something down. When I pull 1 and 4 the car shut off and when I pull 2 and 3 there is no change in idling. Plenty of spark in all four wires. What else can it be???????

[delta448]

Originally Posted by bigblue3643

The car is stock with a stock ecu.

If you're sure you have a 98 ECU and nobody's swapped in an EPROM, we can forget about the CAS sensor style being the issue.

Originally Posted by bigblue3643

So here's what I have done:
Plugs
Wires
Coils
Cam p sensor
Tested all injectors
Reset the ecu and made sure the code was cleared. Fired up the car ran normal for about 5 seconds and then ran like shit. My tach is now dead. I took it for a test run and it would barley move, at times it would run great for a second or two then run like shit. The tach was dead the whole time. Before this problem got worse the tach would do some crazy rotations at any rpm. While the car is idling ( when it want to) I pulled the wires one at a time to try to narrow something down. When I pull 1 and 4 the car shut off and when I pull 2 and 3 there is no change in idling. Plenty of spark in all four wires. What else can it be???????

The tachometer gets it's signal from the Ignition Power Transistor, specifically from the white wire connected to pin 4 of the PT's harness plug. If the tach is dead, then either that wire is broken, the tach gauge is bad, or the PT is bad. With your other issues, I'd lean towards either the harness plug making poor contact or the PT is on it's last legs. Since you do have good spark from both coils, that makes me think it's a bad connection at the PT harness connector.

Another possibility is that your engine has jumped it's proper mechanical timing. Have you checked to make sure that all your timing marks line up yet?

[95'RS-T]

I'd test the ptm, it will cut 2 cylinders off as well as the tach.
How to test the power transistors