Hi.

I've just bought blazer LT 4.3 and I have problem with engine. When idle it runs rough. It jumps from 1500 rpm to 400 rpm. Otherwise the car runs fine and when you drive there is no problem with engine power. I've already checked the engine for vac leaks, fuel pressure and replaced the MAF sensor with new. The funny thing is when I unplug the MAF the car starts running fine. When i checked the DTC I didn't get any except when MAF was unplugged. I have also checked MAF reading and it seams to work fine at idle I have around 23 g/s and at full openthrotle 189 g/s. I have also checked O2 sensors and they also seam to work.

At this point I have ran out of ideas so if there is anybody out there that can help me please let me know.

 

You may just try cleaning the MAF. I had the same problem, but after cleaning it it sure made a difference. Your throttle body may also be dirty. Spray some carb and choke cleaner or sea foam (I recommend sea foam, in the spray can of course) into the throttle body with the intake tube off, and have the engine at almost full throttle to keep it running without the air intake tube. It'll blast out whatever dirt is in the throttle body, and it only takes a few seconds.

That's just a couple of suggestions. Id try them out and see what happens