Hello everyone, this is my very first post here on the forums. I have read around but am having an issue and figured it was time for me to stop lurking and sign up.

I have a 2007 Hummer H3X with 35,500 miles . I have had it for 2.5 weeks now. I changed the oil and filter last week, it was running great. Then I cleaned the maf with maf cleaner, and I cleaned the throttle body a bit with the same cleaner. I had it unplugged. I also changed the spark plugs with the oem ac delco iridium plugs 41 103. gapped to 0.43 I put everything back together and it started idling really bad, shaking and such. I got the cylinder 5 misfire code and had changed the coil packs around. then I got the cylinder 3 misfire code. changed the coil packs around again and then I started getting the random misfires code of p300.

I went and ordered 5 new coil packs and a new maf. Installed them tonight and no change. Still running rough. the check engine light stays steady on until it idles down real low to around 500rpm. then the engine light blinks. if I give it a little gas, it stops blinking. and at around 2,000 rpms it smooths out and is not rough. I need some help here, cause everything was great before I did that work on it.

 

I went through the same problem about a month ago. Did the same things that you did too. To properly clean the throttle body you need to take it out so that you can get to both sides of it. On mine the back side which you can't see when it's bolted on was dirtier than the side you can see. I would do that for sure. After I cleaned the MAF sensor and the throttle body mine still had a rough idle. Was getting random misfire codes just like you too. My G.M. garage told me to change the purge valve. It costs about 45 dollars at your G.M. dealer. I posted a thread that illustrates the steps in changing the purge valve. As soon as I did that everything cleared up. No more rough idling and codes were gone. I don't know if this is your problem, but it sounds just like what was going on with ours. After replacing coil packs, plugs, sensors, it all came down to the purge valve. Let me know if you find my thread on replacing it. If you don't find it, I'll post the link here.

 

Thanks so much for that. please post it here for me. I can check into it. I dont know what this purge valve is all about, but I didnt have an problems at all until I cleaned the maf, throttle and changed plugs. Like I said, now I put in a new maf and coilpacks and its running so rough.

 

Actually I found it and will take a read over it now. thankyou.

 

Ok. I didnt get a PO455 code though. and im not idling High. I think that might be a diff issue. Not to mention I was running fine until cleaning maf, throttle body and changing plugs.

 

undo what you did (the plugs) and see if things go back to normal

 

the plugs I took out were the same exact ones. ac delco iridium 41 103. they are trashed now, because when I was checking the gap on them, the center part broke on them as they were so old.

 

anyone else been in this situation or can help me out?

 

A plugged or leaking purge valve can cause a rough idle or a high idle. Ours just happened to be a high idle.

 

I understand what your saying, but why would that have happened at this time? I didnt have any issues with the truck. I have only had it 2.5 weeks. I was just doing an oil/filter change, and then maf clean, throttle body clean and spark plug change. Thats all I did. I just wanted piece of mind that all that was clean and new.