97 Suburban 5.7 P0300/engine light flashing.

[97Kharon]

Hello everyone, I drove from San Antonio to Houston with no issues. While driving around Houston the engine light (steady) came on I plugged my obd 2 in and read code P0300 the next day when I started the truck the engine light was flashing. The distributor and plugs haven't been replaced since I bought the truck. Any advice?

 

[movietvet]

Hello everyone, I drove from San Antonio to Houston with no issues. While driving around Houston the engine light (steady) came on I plugged my obd 2 in and read code P0300 the next day when I started the truck the engine light was flashing. The distributor and plugs haven't been replaced since I bought the truck. Any advice?

That code is pointing to a problem that is effecting all cylinders. First thing I would do is get all ignition components in the same working order with new parts all around. Like plugs, wires, cap and rotor and inspect the innards of the distributor while opened up. The flashing means, FIX IT NOW before the catalytic converter(s) are effected. In your case I would suspect the distributor cap. Usually the plugs and wires fail individually. Do the cap and rotor and for criminy sakes, use AC Delco or Genuine GM. If you remove the cap and look under it, I bet you see moisture or crud in there.

 

[Schurkey]

Hello everyone, I drove from San Antonio to Houston with no issues. While driving around Houston the engine light (steady) came on I plugged my obd 2 in and read code P0300 the next day when I started the truck the engine light was flashing. The distributor and plugs haven't been replaced since I bought the truck. Any advice?

WHICH "obd 2"?

Is your scan tool capable of showing cylinder-specific misfire codes? How about cylinder specific misfire COUNTS?

Cheap-junk code-readers and bottom-feeder scan tools sometimes LIE about the codes displayed. The REAL code might be P0301--P0308, but they display P0300 instead.

P0300 is a valid code...but unless the tool is capable of displaying cylinder-specific codes and counts, you won't know if it's lying to you.

That code is pointing to a problem that is effecting all cylinders.

Yes...IF (big IF) that's the real code.

First thing I would do is get all ignition components in the same working order with new parts all around. Like plugs, wires, cap and rotor and inspect the innards of the distributor while opened up.

YES. I'd also be looking at the EGR system, PCV system, probably fresh O2 sensors all around. Connect a REAL scan tool, verify spark advance including the knock sensor(s), clean the IAC passage and verify IAC operation. Verify EVERY sensor.

As said--get a reading on the misfire COUNTS for each cylinder, find out if the problem is truly "random" or cylinder-specific.

The flashing means, FIX IT NOW before the catalytic converter(s) are effected.

Yup. A flashing MIL means the catalyst is in danger.

In your case I would suspect the distributor cap. Usually the plugs and wires fail individually. Do the cap and rotor and for criminy sakes, use AC Delco or Genuine GM.

The vented cap from United Motor Products is also well-regarded.

 

[97Kharon]

Update: After getting back into SA I bought and installed a new distributor cap and rotor thought I was in the clear however the same code popped up again.

 

[A97obs]

Update: After getting back into SA I bought and installed a new distributor cap and rotor thought I was in the clear however the same code popped up again.

Did you even figure it out the issue or fix ??
I’ve been dealing with exhaust cat issues now today a flashing sel.. p0300
Previous to me bringing any topics to the forum I replaced my 99 suburban distributor in Nov where I bought the vehicle because the distributor screw tab was busted off so the cap was loose .. forcing me to opt for a new distributor. I bought the cardone aluminum replacement!
Seemingly everything’s been running great still feels like it ! But I have the p0300 “Generic stored” code now
I’m already in the midst of getting on top of a replacement cat , the truck since I owned it NOVEMBER 2023 has always been missing a cat off the driver side bank
flex -piped and hasn’t ever really ran bad I’ve even looked at graphing .. I don’t know if it’s all related

 

[A97obs]

That code is pointing to a problem that is effecting all cylinders. First thing I would do is get all ignition components in the same working order with new parts all around. Like plugs, wires, cap and rotor and inspect the innards of the distributor while opened up. The flashing means, FIX IT NOW before the catalytic converter(s) are effected. In your case I would suspect the distributor cap. Usually the plugs and wires fail individually. Do the cap and rotor and for criminy sakes, use AC Delco or Genuine GM. If you remove the cap and look under it, I bet you see moisture or crud in there.

i ran across this thread .. same issue / code today .. so In my case I have a missing driver side cat “Flex-piped which is No new news here ‘ I’ve topic this recently and am in the process of doing new exhaust components/ but I wonder why the 0300?
I did a new cap and entire distributor/ Nov 23 I had to the truck had a broken dist cap tab “Loose cap “ so I bought a new aluminum cardone dist.

Truck runs like it should at least it feels like it does great on gas even tho i’m sure on scan tool graphing something prob looks way wrong the computer probably sees things with no driver side cat.

Anyway my SEL flashes 5 times 3 sets of flashing . It just began Can something other than an actual misfire throw a false misfire code ? Something That’s like a single incidental moment ? Like if it’s just a bad cat clogging or reading wrong can it set a 0300 if your actually having No fuel spark misfires ? I have new plugs new dist new rotor cap .. ain’t now way it could be bad already

I’ve reset the code in the mean while , to see when or if anything triggers it again and how long it takes , but the driver cat missing and being driven for however long Prior to me owning the truck No-one knows what it has done or could do.

 

[HotWheelsBurban]

i ran across this thread .. same issue / code today .. so In my case I have a missing driver side cat “Flex-piped which is No new news here ‘ I’ve topic this recently and am in the process of doing new exhaust components/ but I wonder why the 0300?
I did a new cap and entire distributor/ Nov 23 I had to the truck had a broken dist cap tab “Loose cap “ so I bought a new aluminum cardone dist.

Truck runs like it should at least it feels like it does great on gas even tho i’m sure on scan tool graphing something prob looks way wrong the computer probably sees things with no driver side cat.

Anyway my SEL flashes 5 times 3 sets of flashing . It just began Can something other than an actual misfire throw a false misfire code ? Something That’s like a single incidental moment ? Like if it’s just a bad cat clogging or reading wrong can it set a 0300 if your actually having No fuel spark misfires ? I have new plugs new dist new rotor cap .. ain’t now way it could be bad already

I’ve reset the code in the mean while , to see when or if anything triggers it again and how long it takes , but the driver cat missing and being driven for however long Prior to me owning the truck No-one knows what it has done or could do.

I have had good performance from the United Motor Products vented distributor cap and rotor, that I got from Rock Auto, on my two Vortecs. They have brass contacts, and the cap has a vent on it that allows humidity to escape instead of rotting/rusting everything inside the distributor.

 

[A97obs]

I have had good performance from the United Motor Products vented distributor cap and rotor, that I got from Rock Auto, on my two Vortecs. They have brass contacts, and the cap has a vent on it that allows humidity to escape instead of rotting/rusting everything inside the distributor.

I have had good performance from the United Motor Products vented distributor cap and rotor, that I got from Rock Auto, on my two Vortecs. They have brass contacts, and the cap has a vent on it that allows humidity to escape instead of rotting/rusting everything inside the distributor

I couldn’t locate that as an option for a 99 5.7 vortec when I looked

 

[HotWheelsBurban]

I couldn’t locate that as an option for a 99 5.7 vortec when I looked

Interesting.... because I had no trouble looking it up or getting it for my '99 5.7 L31 Burb.
Edit: see screenshot.

 

[Schurkey]

I have a missing driver side cat “Flex-piped which is No new news here

I wonder why the 0300?
...my SEL flashes 5 times 3 sets of flashing .

Is your scan tool capable of showing individual cylinder misfire codes?

P0300 is a valid code. However, many bottom-feeder cheap-junk scan tools and code-readers default to P0300 when the REAL code is P0301--P0308.

What are the misfire COUNTS for each cylinder? When does it misfire--at idle, cruise, under load, engine cold, engine warm, etc.? WHICH and HOW MANY cylinders misfire?

but the driver cat missing and being driven for however long Prior to me owning the truck No-one knows what it has done or could do.

I think you're putting WAY too much emphasis on the missing catalyst causing engine problems. Everything the catalyst does, is done AFTER the engine has finished with the fuel-air mix; and AFTER the upstream O2 sensors have sampled the exhaust.

Yeah, that's something that should be fixed...but I'd fix it AFTER the misfire has been solved. Misfire can murder the new catalysts.