I have a 2001 4door 2wd around 110 thousand miles on her..... Im having a prob. I have been having this misfire. I have had it in the shop a few times with this prob.They have done a lot of things like replaced the lifters and basic tune-ups and omg to the point of replacing every part to my blazer =( . But today as my light keeps going on and off I went and got the code scaned an it said random misfire. Well yum yeah been having that for a few months. Plz can anyone tell me what else could be giving me that code and the misfire while driving a sitting at a light. It be nice to take off and not feel I have to put her to the floor to move =( .. Sorry for the long post i'm a girl going crazy on whats going on with her....

 

first, you need to list everything that's been done to her, and be thorough.

no sense in trying to give you a possible solution, if it's already been repalce/fixed.

 

I had a tune up done all the normal stuff,distributor replaced 2 times,all o2 sensor 2 times, all lifters replaced, new intake gasket new head gasket ,gas tank dropped an cleaned out, fuel lines cleaned, some vac lines replaced. All the stuff didnt need to be replaced, but they did to make sure if some of the stuff could of caused the problems. So i'm still getting the misfire and ruff take-off. Took it to autozone and had it tested and said multiple random misfire. Also my check engine light pops on and off. So if anyone could help would be awesome. Love to get my girly fixed.... Thanks

 

might want to look into 'seafoam'. search it up. You could have something as simple as a plugged fuel injector. blasting a can through the fuel tank, and another through the throttle body (or boster lines if you feel that way is better). can't hurt anything, and at $12 total investment, you could do worse...

lastly, fire up the iPod and put a little time into this baby All About P0300

 

What kinds of spark plugs? put ac delco platinums in it

 

X2 on the Delco brand.
these 2nd gen's are picky about what they run with, and seem to run better with all AC Deco brand products in them.
IMO, i don't think you need to run the Platinum's in it though.

 

I had the same thing happen to me. A light went on when you said you replaced the intake manifold gasket. Mine would idle rough, start out rough but then even out as I drove it. Once in a while even stall. Same codes as you, random misfire. My neighbor on the corner, Thank God , is a master mechanic and has every meter that any shop has.

Turns out when I put the plug back in for the fuel injectors, the very large plug that is on top of the Spider unit, I bent one of the little pins. I was careful as heck and it still happened. When this happens it sends a bizarro signal to the on board computer and at idle or stopped it runs rough but when you get going, the computer compensates for it and it actually gets it to run very smooth. Sounds exactly what happened to me. Suggest you check that first

 

have the cam and crank sensors checked out they seem to cause headaches for diagnosing random misfires, i just fixed a car with a dead miss only at 3500 rpm and i checked EVERYTHING except the crank sensor, the crank sensor was the problem. just an idea....

 

You'd be surprised. If seafoam is anything like GM's top engine cleaner, it could possibly lead to premature pump failure. GM recommends not putting TEC in your tank just for that reason. When they clean your injectors, the pump it out of a machine straight into the fuel rail or injector assembly. I forgot which exactly. I'm almost convinced that seafoam had something to do with my pump failing after a year. I used seafoam just about a month before it went out.

 

you also have an 8 y/o fuel pump on a vehicle whos fuel pump is known to be garbage...
plus, if you seafoam correctly, you would just pour a bottle straight through you throttle body, or 1/2 and 1/2 through TB and booster line. pouring it into the fuel tank is really not that effective since it dillutes it's ability to clean, but it COULD help if there are buildups/crud on the way.
unless you pour a can in the tank, the fuel pump should have 0 dealings with the seafoam...