MAF causing P0300

[Black8GV6]

So when my MAF sensor is unplugged the car runs pretty much normal and no P0300. When the MAF sensor is plugged in I get two P0300 ses and car hesitates and has power loss and according to my “mechanic” friend the exhaust note sounds like the timing is off.

I've searched online and haven't found anything useful. I have replaced the spark plugs, got a MAF from the junkyard, new O2 sensors, and switched ECUs.

P0300 started showing up when I put on my headers and 6g74 intake manifold. For my intake manifold I have the egr tube with a breather on the end. Any suggestions what I should check next?

[Black8GV6]

Just read a post on Club3G, I'll check for a vac leak, thanks silvertune

[Rodriguez]

im having similar issue, when you give it gas does it almost completely bog down?

[8thLS6]

Wonder if cleaning the maf will help, but since you said it happen after the headers and IM, not sure

[Silvertune]

You can't clean a karman vortex MAF.

[mko]

The open EGR tube introduces a post MAF leak, all sort of shits happens with that. Remove the filter and plug the tube.

Post a pic of the filter, im curious to see it

[Silvertune]

If he removed the valve then yes. Putting a breather on the tube and leaving it otherwise set up has been practiced for many years and never caused an issue. However I've seen EGR issues result in po300 when the valve opens outside the ecus direction whether its got a filter on it or the pipe.

[Black8GV6]

I'm back on the stock intake manifold. I changed the EGR setup, now i have the ERG tube cut with 3/8 rubber fuel line inside it secured by electrical tape and then the other end of the 3/8 fuel line is connected to the rear valve cover vent (The vent that goes from the rear valve cover to the air intake). So the intake tube has a breather on it where it used to connect to the rear valve cover. I plugged in the MAF with the new setup and still get P0300, so I run MAF free for now. Not the best solution but the car runs smooth MAF unplugged. Still looking for a solution to solve the issue.

[Black8GV6]

im having similar issue, when you give it gas does it almost completely bog down?

With the MAF plugged in, car hesitates soo bad and then it kicks in and takes off like wild horse, all the time. Try unplugging the MAF and see how it drives.

[mko]

Did you disconnect the battery? Fuel trims need to be reset first.

The only time I've seen engine running better w/o a MAF is when the sensor ground is blown. IDK, i still think you have post MAF leak.

[Black8GV6]

I always disconnect my battery, so much so I got tired of putting in my radio code, LOL. I also have a OBDII scanner I clear the codes with. I'll check the ground wire to see if it's loose in the pigtail, maybe it got yanked on.

[mko]

the ground for the MAF, MDP, TPS is artificial and its in the ECU. Its the ground for all 5volt sensors. if you have diagrams, trace it to the corresponding pin on ECU

[Silvertune]

I'm back on the stock intake manifold. I changed the EGR setup, now i have the ERG tube cut with 3/8 rubber fuel line inside it secured by electrical tape and then the other end of the 3/8 fuel line is connected to the rear valve cover vent (The vent that goes from the rear valve cover to the air intake). So the intake tube has a breather on it where it used to connect to the rear valve cover. I plugged in the MAF with the new setup and still get P0300, so I run MAF free for now. Not the best solution but the car runs smooth MAF unplugged. Still looking for a solution to solve the issue.

Dude... are you fucking serious? What do you think that breather does for you? IT CAUSES A MASSIVE AMOUNT OF UNMETERED AIR TO ENTER THE INTAKE. That is the cause of all your problems, point blank. Put that breather on the EGR pipe and rehook the rear PCV vent to your intake tube. Plug in your MAF, reset the battery, and it'll run like stock again.


Holy jesus fuck. I just gotta say, I've seen a few people put breathers on the the PCV vent in the intake tube... My god... I mean fuck. WHAT DOES THE MAF DO PEOPLE? IT METERS AIR GOING INTO THE ENGINE. IF YOU LET AIR IN AFTER IT IT DOES NOT GET METERED AND YOU HAVE A VAC LEAK WITHOUT THE VAC LEAK.

The ONLY ACCEPTION to this is the EGR. There is a fuel compensation added when the ECU opens the EGR, it expects to have a certain amount of unmetered air enter which allows you to put a breather on the EGR pipe and run without problems. The intake does NOT WORK THAT WAY.

[Black8GV6]

will a Y connector work, between the rear valve cover, the EGR and the intake pipe nipple?

[Silvertune]

will a Y connector work, between the rear valve cover, the EGR and the intake pipe nipple?

No... The EGR needs a BREATHER. It is designed to pull UNMETERED air. Hook the PCV up like its supposed to be and a breather on the EGR, no other way.

[Black8GV6]

^ that's how I had it and kept getting the P0300

[Silvertune]

Then straight plug your EGR. You don't have it run right or one of the control pieces is shot. You've had the same problem the whole time, you've just changed sources. The MAF has to meter everything that goes in minus that which the EGR passes when the ECU tells it to open. Your EGR is opening all the time.

Plug it and rerun the PCV. Plug in MAF, reset battery and deal with troubleshooting the EGR later.

[mko]

will a Y connector work, between the rear valve cover, the EGR and the intake pipe nipple?

I have a similar setup to this, but I have one of TB nipples "t"-ed, The one that goes to before the throttle plate, so when EGR opens it sucks fresh metered air.

[Black8GV6]

I just bought some blocking plates http://www.3sx.com/store/comersus_vi...idProduct=1074 I remember Keith bought them, thanks Keith!

[Silvertune]

You realize simply unplugging the vac line on the top of the valve will do the same thing right? Assuming your valve is functional and actually closes.