Hello! I've been having a problem with the blazer (2001, 2WD LS) the past couple weeks. While in drive or reverse it has a rough idle and gets worse once stopped at a red light. The rpms will drop and oil pressure will too, the engine sounds like it wants to die...almost choking, sputtering sound. When stopped at a red light and these symptoms start happening, it will hesitate when taking off. When symptoms started the first day, SES light came on, read cylinder 3 misfire. Light came on while just sitting in the driveway. I erased it. Then yesterday, light came on and started flashing while I was going home. The light would stop and start again with the blinking a few times. But while vehicle is in park, it is just fine and no odd sounds.


Now I would love some advice on where to start and such. This thread is also to help me keep track of this problem and possibly help others.


I have recently cleaned the maf, egr, throttle body. Changed out fuel pump, filter and injectors but haven't had a rough or hard start since changing the injectors out. Haven't done a leakdown in a while but without a hard start, I'm thinking those are still good. Thanks guys!

 

Mama Mia!!! That's a lotta decibels!!! Like a jet engine at 10 yards. I think you drove by my house last night!!

Couple of questions? Where do they actually measure the sound? What frequency gives the 150? Is it from bass pulses or is it more continuous and higher frequency?

I had a friend once tell me my car stereo was going to make his ears bleed, but nothing like this.

 

Ha, Thanks man! I love my hobby! The organization that I compete in down here in the south is called MECA - we meter at the headrest. We build a stand to hold the decibel meter - 26" from the bottom of the seat, 20" from the windshield. The decibel meter we use is called the termlab, it's the most accurate on the market - nasa uses it to meter the level of take offs.


Right now, my peak frequency is 49hz. The peak though can change in a heart beat if you increase box size, port size and length, or just moving the box a couple inches. It's all physics. And it's just one note, 3 seconds is all you need. There's plenty of videos on my youtube link. I'm the white blazer, 2 door if you look thru them.


I've never seen anyones ears bleed, lol. I've sat in some loud vehicles, the worst thing that happens is you cannot breathe to save your life lol.

 

With new fuel pump and injectors, I am thinking maybe vacuum leak or ignition problem. Can you monitor the two front oxygen sensor voltages or the short term fuel trim during the rough idle and provide a freeze frame from when the misfire code set. I think those things should reveal enough to get started.

BTW, that's a very nice Blazer in the videos.

 

Thanks man! I can do that soon. Going out of town this weekend. It did freeze frame during one of the misfire codes. Not sure if that'll help or not. I'm in the middle of replacing the spark plugs and wires. I pulled them all, just waiting on the new ones. I will say though, I'm optimistic about it being them since I pulled the wire off of cylinder 3 and half the plug was filled with black powder, kind of like a soot material. I knocked it on the ground and it was a lot. I think one other plug had just a bit of that, others were ok overall looking. Since I believe they are original, going to replace them anyways. We've had the blazer in the family since it had about 40k, no record of the wires being changed. The spark plugs have about 60k on them. NTB put them in a long time ago, had no clue what plug they were, pulled them and they are ngk spark plugs. But replacing them anyway. AC delco everything.


I have also replaced the cap and rotor a while back ago when I did the fuel injectors. Hopefully by Monday I can report back once I get home and work on them.

 

So changed the spark plugs and wires. I was able to just use a wobble extension and a knuckle adapter I believe is what it's called. I have driven about 30 miles but problems cleared up instantly and haven't come back yet. Not sure which one it really was but my money was on the wire. If anything else comes up, I'll update it.

 

Glad to hear it's fixed. Thanks for the follow up post