P0300 Misfire in all cylinders 2001 Tahoe

[Nicolai8775]

I don't understand. I've been fighting some idle issues after a TBSS intake swap and a bigger cam. During the scan cable process, Blackbear said I had a small leak probably at the intake but the tune is good to go. I sprayed starter fluid on a cold motor around the intake and TB and didn't hear any changes. I found a weak spot on the evap line, my EGR delete wasn't capped off properly, and the MAP sensor wasn't secured well enough. I fixed all these issues and now have p0300. Torque shows it's happening in all cylinders A LOT. After I fixed those leaks the idle issue went away except now it misfires terribly.

It has new plugs and wires, I've triple checked every injector and spark plug wire and nothing is crossed.

Is it a fuel delivery issue? The FAQ I used as a guide to modify the fuel system mentioned the C5 filter/regulator holds a static 58psi and I should tell the tuner to account for that. Well I didn't do that because I overlooked that on the FAQ lol. This doesn't make sense to me since I did a scan cable tune. Would he not see this?
Do I need a bigger fuel pump to power the 36# injectors that are bigger than the stock #26 injectors?

Is it timing? I had a timing chain dampener but someone I talked to at Summit said I shouldn't need it. Now I'm wondering if he didn't know what he was talking about.

I would be happy to post logs if someone can help me diagnose. I don't fully understand what to look for.

 

[Nicolai8775]

Ok I tested the fuel pressure at the rail. I'm getting 63 psi lol. So that's way higher than the stock 40-50 psi and higher still than the C5 regulator that demands 58psi. Am I getting to much unburnt fuel that's fouling my plugs and causing a misfire?

How do I get the pressure down? Tune? Remove my stock fuel filter?

 

[live2pull]

I had p0300 when I replaced plugs and wires, turned out my budget wires were not adequate, purchased some delcos and was right as rain after that. I think you might be on the right track though with fuel pressure and plug fouling as a result. May want to contact your tuner and ask?

 

[OR VietVet]

Remove some of the plugs and see if they are black, indicating too rich and fouling the plugs. Plus, like has been said, quality parts make a big difference.

 

[Nicolai8775]

I had p0300 when I replaced plugs and wires, turned out my budget wires were not adequate, purchased some delcos and was right as rain after that. I think you might be on the right track though with fuel pressure and plug fouling as a result. May want to contact your tuner and ask?

I checked #1 cylinder plug and it had a faint smell of gas, not wet, and nothing burnt on it.

The plugs are ACDelco 41-162.

Lol the plug wires are Ultima select I think oreillys brand

I've emailed Blackbear but unfortunately he only goes by email and it takes a week or 2 for a reply every single time. It's slow going.

 

[OR VietVet]

I checked #1 cylinder plug and it had a faint smell of gas, not wet, and nothing burnt on it.

The plugs are ACDelco 41-162.

Lol the plug wires are Ultima select I think oreillys brand

I've emailed Blackbear but unfortunately he only goes by email and it takes a week or 2 for a reply every single time. It's slow going.

Just like the best shops and techs in town, they are hard to get in line with for work and info. That rich look I was talking about can be wet like you saw or a black soot look and the spark plug insulator will be black soot looking as well. If the plug is wet that means that the plug is not firing either at all or intermittently.

 

[Nicolai8775]

Just like the best shops and techs in town, they are hard to get in line with for work and info. That rich look I was talking about can be wet like you saw or a black soot look and the spark plug insulator will be black soot looking as well. If the plug is wet that means that the plug is not firing either at all or intermittently.

This is the #1 plug, I can pull more after I get off work in a bit. It looks fine to me. The threads looked slightly wet and faint gas smell. But nothing was burnt on.

 

[OR VietVet]

It looks fine to me. I would still check all of them and remember what cylinder each came out of. Those plug wires? Are they the big thick 8.8 mm wires?

 

[Nicolai8775]

It looks fine to me. I would still check all of them and remember what cylinder each came out of. Those plug wires? Are they the big thick 8.8 mm wires?

They're definitely just a standard looking plug wire.

 

[OR VietVet]

GM P0300 Causes (* = Most Common)

• Faulty or worn spark plugs *
• Faulty spark plug wires or coils *
• Distributor failure *
• Faulty fuel injector *
• Vacuum leak
• Low fuel pressure
• Camshaft sensor defective
• Crankshaft sensor defective
• Engine timing off
• Leaking head gasket
• Low engine compression
• Poor quality fuel

With the work that you did you may have some problems with the cam or crank sensor.

 

[Nicolai8775]

GM P0300 Causes (* = Most Common)

• Faulty or worn spark plugs *
• Faulty spark plug wires or coils *
• Distributor failure *
• Faulty fuel injector *
• Vacuum leak
• Low fuel pressure
• Camshaft sensor defective
• Crankshaft sensor defective
• Engine timing off
• Leaking head gasket
• Low engine compression
• Poor quality fuel

With the work that you did you may have some problems with the cam or crank sensor.

Well I did lifters and pushrods stiffer springs and everything so now I'm worried about compression or leaky head gaskets lol.

And to be honest.. I'm worried about timing too. If all the dots are lined up right. Cam sprocket at 6 o'clock, crank sprocket at 12 o'clock. And the cam "pin" is at 3 o'clock on the cam sprocket. Is the #1 piston at TDC? We didn't do any of that process with the screw driver in the #1 piston hole to find TDC.

 

[ks03]

Having a new cam and intake, might hookup a vacuum gauge. If it’s too low, bounces or fluttering it might give a direction where to go, or hopefully eliminate mechanical issues

 

[OR VietVet]

Well I did lifters and pushrods stiffer springs and everything so now I'm worried about compression or leaky head gaskets lol.

And to be honest.. I'm worried about timing too. If all the dots are lined up right. Cam sprocket at 6 o'clock, crank sprocket at 12 o'clock. And the cam "pin" is at 3 o'clock on the cam sprocket. Is the #1 piston at TDC? We didn't do any of that process with the screw driver in the #1 piston hole to find TDC.

I have never done the TDC check with a screwdriver. I have #1 plug out and finger tightly over the hole and bump the engine till compression pushes finger off hole. You are on the compression stroke at that point. Line the timing mark on balancer with the TDC mark on the timing tab and you are TDC. If you set the cam and crank sprockets at dot to dot, they are correct. If you are just one tooth off, there is your problem. The dots would line up dot to dot with everything straight up and down at 12 and 6 o'clock. Vacuum gauge is great to hook up and get a reading. Normal reading would be a steady 18-22 inches at idle. You could have an intake not seated properly? Get a vacuum reading first. I like to take pics of major teardown work, now that I have a cell all the time. That way I can check for the timing marks align when an old fart like me asks.

 

[Nicolai8775]

I have never done the TDC check with a screwdriver. I have #1 plug out and finger tightly over the hole and bump the engine till compression pushes finger off hole. You are on the compression stroke at that point. Line the timing mark on balancer with the TDC mark on the timing tab and you are TDC. If you set the cam and crank sprockets at dot to dot, they are correct. If you are just one tooth off, there is your problem. The dots would line up dot to dot with everything straight up and down at 12 and 6 o'clock. Vacuum gauge is great to hook up and get a reading. Normal reading would be a steady 18-22 inches at idle. You could have an intake not seated properly? Get a vacuum reading first. I like to take pics of major teardown work, now that I have a cell all the time. That way I can check for the timing marks align when an old fart like me asks.

I may tear into the timing again then. But, before that, I did just notice a split in the insulation in the 1 wire for that camshaft position sensor.

 

[OR VietVet]

You might do yourself well by replacing the can and crank sensors and make sure all wiring is intact. make sure when you plug wiring back in that the wire stays encased in the connector tab and does not push out of the connector.

 

[Nicolai8775]

You might do yourself well by replacing the can and crank sensors and make sure all wiring is intact. make sure when you plug wiring back in that the wire stays encased in the connector tab and does not push out of the connector.

It's a 1 pin connector, can't find anything like it on oreillys site.

 

[Fless]

Aren't the cam and crankshaft sensor connectors 3-pin?

 

[Nicolai8775]

Aren't the cam and crankshaft sensor connectors 3-pin?

Well I guess that means I'm taking the intake off cause that wasn't the camshaft connect lol. But I'm confused. It's bolted downwards on the back of the block, behind the intake, what else is back there that I could have grabbed?

 

[Nicolai8775]

Aren't the cam and crankshaft sensor connectors 3-pin?

This is what I'm looking at.

 

[Nicolai8775]

Aren't the cam and crankshaft sensor connectors 3-pin?

Yeah you're right damn it. There's something else deeper down lol.