I have creeped around the forums for a week now looking for tips that could help me fix this Blazer

Problems: Temp running 226-230, rough Idle pretty often, AC blower motor cuts down to almost nothing then comes back on full blast even when not on "auto".

What I have done: Thermostat, plugs, wires cap and rotor, pcv valve (inspected elbow and hose also), thorougly cleaned throttle body, installed fuel pressure control module, fuel pump, fuel filter, new water pump, flushed it 4 times, pressure checked cooling system with 15 lbs of pressure, it leaks off pretty quick but shows no signs of coolant leaking on exterior of vehicle.

Performed carbon monoxide test on cooling system to check for blown head gasket, it passed the test (no exhaust in cooling system). Also check oil multiple times, no sign of water/coolant and level is exactly the same.

I have spent a fortune on parts on this thing, and a ton of labor also. I would really appreciate some helpful insight or tips here.

My current thoughts: leak in intake, or blown head gasket, or possible bad radiator although it appears to flow very well.

 

Heat works ok? Still air maybe in cooling system? Also I've had the lower half of the radio clogged on mine caused trouble

 

Yes, heat works great. Filled with front right tire jacked up to make radiator cap the highest point.

 

Update: Just completed checking and cleaning the heads and installing new head and intake gaskets. The problem still persists. It runs out fine for 10-15 miles at 210 or just shy of it, but when pushed to 55-70 mph and through hills etc, it begins to overheat to 245 degrees.

When its running 245 or so, it lacks for power, same as before. Especially when taking off from a stop. Then once you get up to 35 or so its as if you can feel it start freeing up and the resistance "lack of power" begin to reduce. While accelerating trying to pick up speed etc, the blower motor cuts way back, then once you get up to speed and let out of throttle, blower motor starts blowing hard again. It does this whether on "auto" or high. Also when you stop at stop signs etc when its hotter than desired range (ie 145) ..., it cuts out and runs so rough you think its going to die. It only cuts out and runs rough though when you come to a stop.

Myself and a few other guys that have assisted with the work are extremely stumped as to what is causing all this.

I have ordered a new radiator that will be here tomorrow, and also will be replacing the catalytic converter. Hopefully this helps! I feel terrible throwing parts and money at this, but At this point, I don't know what else to do. The radiator will be the only piece of the cooling system that has not yet been replaced.

 

If you did the intake and head gaskets I would think a radiator could be the next logical step. How about the water pump and radiator hoses?

 

Replaced water pump last week. I will replace the hoses when I put the radiator in today.

 

Your symptoms sound like a clogged radiator and/or a collapsing lower radiator hose.

Did you replace the fan clutch when you did the water pump? Those are supposed to be done together, but most places ignore the fan clutch until it gets so bad it starts destroying water pumps.

 

Yes sir. Same time.

I replaced the radiator today and radiator hoses. I haven't got it to overheat since (drove a very hard 25 miles.)

The rough idle when warmed up and in gear problem still persists though. Smooths out some when put in Park, but then hold the brakes and put in Drive, and it runs rough as can be. Also when you first start it and take off the first time, it has very low power/very weak takeoff. It does better once warmed up on taking off from a dead stop.

 

rough idle could be a lot of things, poor quality ign. parts. These trucks prefer ac delco at least for the cap rotor and plugs. wires could be arcing also. look under the hood engine running in the dark at the wires and look for sparking. could also be a vacuum leak. check the the free stuff first before throwing more money into it

 

By rough idle, do you mean that it idles OK, then coughs or stumble from time to time? And the engine shakes when it sputters? Does it clear if you just barely press the gas pedal? Those symptoms are usually a dirty idle air control valve and clogged idle air passages in the throttle body.

Get a couple cans of "throttle body/intake" cleaner. Pull the idle air control valve. It's behind the throttle position sensor on the driver's side of the throttle body. There's a narrow air passage from the top of the throttle body behind the throttle bore down into that area. You'll probably find a bunch of carbon on the IAC valve plunger, and enough black "charcoal" in the air passages to have a barbecue. It's a little easier to thoroughly clean all the passages if you pull the throttle body off the plenum. Clean the bore for the IAC vlave, the passage above and the passage below until you see all shiny, clean aluminum, and clean the IAC valve plunger until it's nice and smooth. Put everything back together and see how much that improves things.

If vibration and noise are more noticeable when in drive than in park or neutral, your motor mounts might be week/broken as well.