2007 hummer h3 engine misfire diagnosis

[Dub-NUb]

2007 hummer h3 engine misfire diagnosis RESOLVED

Hey guys I'm needing some help troubleshooting my hummer h3.
Problem: getting engine misfires and p0300.

All cylinders are misfiring every now and then. This happened after the following was resolved; coolant thermostat replaced, passlock module replaced.

I have put seafoam injector cleaner and no help.

Here is what I have found. When the engine starts to acts up and I touch the orange wire (ground wire) on map sensor the idle begins to dip and engine misfire. When I let go the car acts better but still misfired..just not to the point of stalling.

I ordered a new map sensor thinking it was faulty but the issue still remains.

Car drives without any issues with map sensor disconnected but I get traction control failure light.

Anyone know the ground points in the engine?

Thanks for your time.

 

[Bruces]

Check your coil pack harness where the split for each cylinder. I had a chaffed wire on cylinder 4 the was touching valve cover. I have an 07 i5

 

[mjferencak]

I read somewhere it might be the vapor canister/solenoid malfunctioning and this is why the p0300 code shows.

 

[Dub-NUb]

I read somewhere it might be the vapor canister/solenoid malfunctioning and this is why the p0300 code shows.

I replaced that canister in the back under truck.

I feel like there is a ground wire somewhere because when I touch the ground the engine acts up.

 

[mjferencak]

Chase your wires but also check the hose that connects from your valve cover to the air intake. It may be torn and the head pressure may be off causing your problems also.

 

[Dub-NUb]

Chase your wires but also check the hose that connects from your valve cover to the air intake. It may be torn and the head pressure may be off causing your problems also.

The hose from valve to intake plenum is good. I cleaned out throttle body and maf last week in hopes of solving this.

Will check all coikpack wiring because that covering is crumbled and wires are exposed.

I do know that a wire was rubbed down to metal that I found and I put electric tape on it, it went to cam sensor I think.

 

[08H3]

I had an elusive P0300 like you. Your MAF issue leads me to believe your caus is different, but mine was a loose intake manifold. Just throwing it out there. Good luck figuring it out.

Also, heard the vapor canister mentioned. I don't think you'll ever get anything but P0449 out of that.

 

[Dub-NUb]

I had an elusive P0300 like you. Your MAF issue leads me to believe your caus is different, but mine was a loose intake manifold. Just throwing it out there. Good luck figuring it out.

Also, heard the vapor canister mentioned. I don't think you'll ever get anything but P0449 out of that.

Mine is the MAP wire issue.

 

[Dub-NUb]

I am thinking my ground wire may have been done for because I just pulled on it with a little pressure to try and pry it loose from the connector and it broke clean off. The other two wires are nice and firm

 

[Dub-NUb]

Update: fixed the ground wire on MAP sensor and so far so good. I will drive around today and see how it idles and if all is well then consider it fixed. Will be returning MAP sensor , save $50.

 

[Dub-NUb]

Update 2: the issue is resolved.,culprit was a broken ground wire under coating on MAP sensor.