Help ! 1996 Tahoe P0300 any GM tech here this is not a easy one

[Ridgerunnerras]

History

2 years ago I replaced the spider pop-it with a upgraded mutil port Spider do to a failed fuel regulator diaphram leaking fuel in the intake causing a p0300 code and running like crap. then it ran great

this last spring I replaced the Fuel pump as it failed. then it ran good again.

this last weekend I was driving it and had to hit the brakes hard at a stop light. the engine started missing and again the p0300 cam up. no matter what RPM it is is alway missing and sounds like it is running on 5 cyl.

so to day I replaced the cap an rotor just because and it had been sitting fo 2 days. I started it up and it ran Great and I was happy again (so was the wife it is her car).

so just to make sure everything was good I drove it in to town and back (about 10 miles) and when I was almost home I hit the brakes and the same thing happened. now it is running like crap again.

So I thought Brake booster vacuum leak. so I pugged the booster hose but no change.

The only other thing I can think of is maybe there is water in the tank from a bad batch of gas.
Th fuel Pressure is good between 56 and 62 and jumps to 62 when I accerate. It does not leak down when shut off.

Any Ideas???



have any of you had this problem before?

 

[Phone Man]

I'll be watching this one. I've been chasing a p0300 for over a year now.

 

[SunlitComet]

When you are slamming on the brakes is there gas enough that you are not sucking air? Are the electronics grounds clean and intact on thermostat housing and rear of right cylinder and does it gets worse under load?

---------- Post added at 04:19 PM ---------- Previous post was at 04:17 PM ----------

Also did the fuel pump replacement include the connector update.

 

[Ridgerunnerras]

I have 1/2 tank of fuel . if it was Sucking air then when sitting still it Should get better, but it does not.

yes the new pump has a new connector all soldered and Shrink tubed

I can Check the ground tonight and see if there is any voltage drop from the engine ground to the battery. and ohm it out.

it does not get worse when acceration occures it is like you pulled 3 of th plug wires off and tried to drive it.

 

[bubbz]

Could this be the lower intake leaking... I have the same problem and I noticed that the coolant is slowly going somewhere..... could be un related problems but I don`t know what symptoms the lower intake leak will give

 

[Ridgerunnerras]

Could this be the lower intake leaking... I have the same problem and I noticed that the coolant is slowly going somewhere..... could be un related problems but I don`t know what symptoms the lower intake leak will give

I have replaced that gasket with a new metal/rubber one.

the stock ones are plastic and they crack and dump coolent in the motor so you might want to consider replacing it.

 

[sbowen]

That sucks

Wow you got a real live gremlin there. Good luck.

 

[1999hoe]

Any word on this ? Im.chasing my own p0300 changed plugs cap rotor seems cylinder 3 is my biggest multiple misfire however it shows yhe history as misfires in all cylinders but number 3 is over 30k for some reason