my wifes 2007 H3 has about 125k miles & recently started to take spells where it idles rough for few seconds then idles fine. It showed a P0300 code once (random misfire)

I've run couple bottles of fuel system cleaner thru, changed air filter, plugs, coil packs, & cleaned the throttle body. It runs fine on the road. When u stop at a light, it might go to a near stall while idling.

any suggestions?

 

[QUOTE=kwm1971;337115]my wifes 2007 H3 has about 125k miles & recently started to take spells where it idles rough for few seconds then idles fine. It showed a P0300 code once (random misfire)

I've run couple bottles of fuel system cleaner thru, changed air filter, plugs, coil packs, & cleaned the throttle body. It runs fine on the road. When u stop at a light, it might go to a near stall while idling.

any suggestions?[/QUOTE

Check the vacuum hose under the reservoir intake the hose to be loosed or damage

 

Check the vacuum hose under the reservoir intake the hose to be loosed or damage

 

U mean the short hose at the back of air box that goes from air box to engine ?

 

Lol! That's actually called a resonator box and the black hose (part #15123628).
I believe it's name is air intake breather hose or some such thing. It's like a pcv hose. Lol. By the way my gf's h3 has done that shaking bit since she bought it. Never could figure it out to this day.

 

Yeah the hose under the airbox that hooks into the valve cover

 

Have you ever cleaned the MAF? You are way overdo if not.

There are threads on both of those topics, search em out and have at it. Use only TB cleaner for the TB, and MAF cleaner for the MAF. Best way to clean the TB is to remove it and reinstall after the scrubbing.

 

Had the same problem for so long 06 H3, jus dealt with rough idle because I thought engine would be going out soon since mileage was over 200,000 Same code. PO300 scanned at autozone, cleaned tb and mass air sensor didn't help. Fuel injector cleaner also didn't help. Last desperate try bought a can of 6 cylinder Restore (silver can) at Walmart and added with oil change, it worked took the rough idling away that would always be felt at stop lights and when in idle at park, was surprising. By the way pushing 312,000 miles

 

Not sure if this is where I need to start, but similar problem.

Have no clue what to do! I have 2006 Hummer H3 L5-3.5L with about 150,000 miles (Vin 5GTDN136968266919 03/06)
First started with a dead battery, AAA came out said bad battery and week/low charging from the alternator. Replaced battery with new. Try to start it, it starts for 3-4 sec. and then ruff idle for 3-4 sec. then dies. I then replace the alternator with OEM New one. Start it and it fires up like normal. I drive for 1-2 short trips with now problem, but DCM pops up with “Service Stab Sys, Traction Failed, Reduced Power” and the check engine light came on as well. I did nothing, Next start it starts for 3-4 sec. and then ruff idle for 3-4 sec. then dies Again.
Found a mechanic to come look at it. He checked codes, sorry for not have the actual codes. The 1st code was for MAF sensor, 2nd was for cylinder miss fire. He says fuel pump, about $650 for new. I told him to wait. He cleared the codes. I would like to price check for one on my own. I research how to troubleshooting fuel pumps before I buy new. I checked the pressure, 55 psi. Then fuses and relays replaced with new. Also, could hear fuel pump prime when turning the key. So I have checked off the bad fuel pump. Note: I can here a wired electrical hum behind the dash that goes on for approx. 1 min will the key is in the accessory, this sound is a new one. I noticed that the low fuel light was on so I added 5 gallons of fuel to check that off the list.
I now think its electrical. So then I tried pulling a few fuses (BCM, TCM, PCM) for a few minutes and reinstalling them and pulled the battery negative cable too. Try start same idle die. Note: My H3 has a sunroof and yes it leaks, I have heard that this has caused others to have electrical issues. Not ruling out electrical, but don’t know where to look next.
Next, I air filter replaced with new. Cleaned throttle body, MAF and intake with intake cleaner, (Yes I took it off and did both sides). Cleaned all sensors in the intake with electrical cleaner. Try and start, the same thing no progress. Once again I pulled the battery cables to reset the throttle body memory, nothing. Checked for vacuum leaks with starting fluid, Nope.
I have the mechanic come back and relay all I have done. He said I was right about the fuel pump by all of my checks. He says it could be a catalytic converter plugged up or bad o2 sensor. He told me to pull one of the sensors before the cat and try to start it and it should run or at least idle and not die, releasing the back presser. So I pulled both of them and unplugged them from their harness. I try again it started, but ran very rough, misfiring, and then died in about 10 sec.
I have read countless threads on this topic, but unable to get a clear answer. Others have similar issues with different results. I’m finally strapped! So I’m trying to do as much of the troubleshooting myself. The nearest dealer is 45 miles away, (have tow it there) unable to do that at this point. My mechanic is really good but just wants to start replacing parts until we find the right one.
What I have learned from other threads. Recall on 06 Hummer H3 on heads, not sure if that could be an issue. Possibly clogged fuel injectors. OEM battery terminal/connectors. Replace my encoder motor, (I have no idea what that is). PCM fuel management glitch, (how to tell?). And accelerator pedal assembly.
Does anyone have any advice for me on this? Noob to your thread, sorry if I didn't follow protocol. Thanks

 

Do you have a sunroof?

With GM products, pulling fuses and disconnecting battery cables doe NOT reset anything, they store the last 300 ignition cycles, power or not.

So you touched on battery terminal connectors...... do you still have the OEM battery terminal connectors? If so, that is where I would start. They are absolute crap, hack them off and replace them with a quality aftermarket set. You notice just how crappy they are as soon as somebody messes with the original factory connection (like when replacing a battery) and they go down hill from there.

Next, make sure your intake manifold bolts are all tight, they do vibrate loose and it is not unusual for some of your symptoms to come from there.

Next, look into a new PPS (Accelerator Pedal Sensor), they are less than $40 and a simple plug and play.

Let us know how that goes.

Fuel pump would be down my list about 10+ more items.