p0300 mult cylinder misfire....

[someday31]

Originally Posted by kahjdh

My money on intake, i have never had a driveability prob with over 50psi. I cant count how many times I have done these and no comebacks so far.

You need to do some more diag though before you go out and drop $250 on an intake.

What could I do to isolate that its the intake though? If it is, would you recommend the Dorman aluminum replacement?

[danielsatur]

I found a good video, see http://www.youtube.com/watch?v=FfiQ7qWiG-M

Unmetered air could lead up to random mifires, and DTC's.

[someday31]

Originally Posted by danielsatur

I found a good video, see http://www.youtube.com/watch?v=FfiQ7qWiG-M

Unmetered air could lead up to random mifires, and DTC's.

Thanks...Yeah if only I had a smoker! I am going try the carb spray near the intake gasket and see if that shows anything as a test!

[kahjdh]

what we do is smoke the intake but you prob wont have access to one of those. try carb clean or propane from a small torch and see if there is an idle difference. also need to do this when the engine is cold.

I just use the plastic kit from dorman, comes with everything and is thicker than oem so they dont warp.

[someday31]

Originally Posted by kahjdh

what we do is smoke the intake but you prob wont have access to one of those. try carb clean or propane from a small torch and see if there is an idle difference. also need to do this when the engine is cold.

I just use the plastic kit from dorman, comes with everything and is thicker than oem so they dont warp.

Now just to be clear, we are talking about the black plastic, upper intake manifold thats long and narrow like this one....

http://cgi.ebay.com/ebaymotors/99-07...Q5fAccessories

[someday31]

Ok just went out....I get 55psi vacuum line off truck in run (not running), I get 59.5 with truck running and vacuum line off, when running I can hear the sucking of the vacuum line, sounds strong. Hooked vacuum back up while running and pressure dropped down to 50/51 again. I could hear a difference in the motor with the vacuum line hooked up and without it hooked up. Btw I did buy a Purolator fuel filter, I like them as well.
What do you think jcat?

[danielsatur]

Back yard smoke Test-
1) Take the air filter out, wrap with glad wrap, and put back in.
The Idea is to block all air going into the Inake system.
2) Disconnect the brake booster hose going to the Inake.
3) Light a Black & mild cigar, blow smoke into the brake bosster vacuum hose going to the Intake, and cover with thumb inbetween puffs.
Any smoke leaks is unmeter air leaks, that needs tobe repaired.

danielsatur

[kahjdh]

He doesnt smoke.

When ever you create a vacuum leak like when you take the line off of the regulator it will affect idle b/c you are letting unmetered air into the system.

[danielsatur]

Smoke Test's are done with the engine off!

Caution - Starting fluids, and other sprays canbe very flammable.

[j cAT]

Originally Posted by someday31

Ok just went out....I get 55psi vacuum line off truck in run (not running), I get 59.5 with truck running and vacuum line off, when running I can hear the sucking of the vacuum line, sounds strong. Hooked vacuum back up while running and pressure dropped down to 50/51 again. I could hear a difference in the motor with the vacuum line hooked up and without it hooked up. Btw I did buy a Purolator fuel filter, I like them as well.

the regulator is working correctly. problem is the fuel pressure is too low.

the spec is 53- 62psi. this is required to get the engine running correctly..the guage your using must be correct/accurate.

many have had this problem as the pump slowly dies.like you it is intermittent as the pressures are low but not so low it will not run.

normally 180,ooomile is what this componet fails at..running on low fuel it will fail sooner.

replace the fuel filter and the relay first . check all connectors grounds to the fuel tank/pump assembly..then replace the pump ..now you will be good for another 180,ooomi...

[someday31]

Originally Posted by j cAT

the regulator is working correctly. problem is the fuel pressure is too low.

the spec is 53- 62psi. this is required to get the engine running correctly..the guage your using must be correct/accurate.

many have had this problem as the pump slowly dies.like you it is intermittent as the pressures are low but not so low it will not run.

normally 180,ooomile is what this componet fails at..running on low fuel it will fail sooner.

replace the fuel filter and the relay first . check all connectors grounds to the fuel tank/pump assembly..then replace the pump ..now you will be good for another 180,ooomi...

Ok I got the check engine light to go off! I took the air cleaner assembly apart and cleaned the mass air flow sensor, I could see that it was cleaner afterwards! The truck sounds much better and runs stronger and smoother, within 2 miles of driving light went out and all codes were gone! It must be the oil from my airaid intake filter?
But my issue is that I reset my mpg calc and I get only 13-13.5mpg around town/country roads. Could my possible fuel pressure issue relate to this?

[brcidd]

Originally Posted by danielsatur

Back yard smoke Test-
1) Take the air filter out, wrap with glad wrap, and put back in.
The Idea is to block all air going into the Inake system.
2) Disconnect the brake booster hose going to the Inake.
3) Light a Black & mild cigar, blow smoke into the brake bosster vacuum hose going to the Intake, and cover with thumb inbetween puffs.
Any smoke leaks is unmeter air leaks, that needs tobe repaired.

danielsatur

What would happen if you lit a stick of incense and push it down the brake booster tube, then held thumb over the tube.

[danielsatur]

If that doesn't work , plug the air filter, and drop your favorite color smoke bomb down the air duct work!

[kahjdh]

you should have said you had an a/m intake on, these are very common b/c gm maf's dont like oil.

[j cAT]

Originally Posted by someday31

Ok I got the check engine light to go off! I took the air cleaner assembly apart and cleaned the mass air flow sensor, I could see that it was cleaner afterwards! The truck sounds much better and runs stronger and smoother, within 2 miles of driving light went out and all codes were gone! It must be the oil from my airaid intake filter?
But my issue is that I reset my mpg calc and I get only 13-13.5mpg around town/country roads. Could my possible fuel pressure issue relate to this?

after the fuel pressure is corrected , you may have other failures. a restricted converter will give a miss fire code. also lower power and MPG. O2 sensors too old also cause poor running ,but with this engine the PCM will quickly throw O2 codes.

dirty maf sensor pick up wires will throw the fuel mixture off some what but ,,, the O2 sensors will have the last say on fuel trim..unless the MAF is defective or not connected.

ON non OEM air filter housings etc....

when in a dry , warm climate you can get some benefit with these devices. when it is very cold , dry, and lots of snow blowing around it is best not to use these air intake devices..

you suck up too much snow/water then the media cannot pass air...an air filter that is wet will not pass much air.