I am having major trouble with my 01 Chevy Blazer. The truck would run great at idle but ran with a heavy bog when running down the road with great power loss. I wen ahead and pulled the codes and found....I started with having codes for the Mass Air sensor so I replaced it. Then I got code for the EGR valve....replaced it and cleaned the EGR tubes. Was advised that I may have a vacuum leak in the intake so I then pulled the upper intake and cleaned the carbon out of it along with cleaning the injectors and replaced all of the intake gaskets. Now it's only remaining code is a p0300(Random Cyl. Mis-fire) so I now have changed the distributor cap and rotor, (the coil, plugs and wires were recently replaced along with the Fuel Press Reg.) and it still wont run on it's own without me staying on the gas. It still has a heavy miss along with an ocasional backfire through the carb and acts like it is only running on a few cylinders.....I am at a loss as to what to replace next. Any Ideas?

I appreciate any help offered.

Ken

 

I had same problem. No power, even at 1/2 throttle.
Remove the 02 sensors (3) of them. Check for carbon/soot buildup. I had alot of carbon buildup on bank 1. Cleaned mine w/ electrical parts cleaner. Reinstalled them and reset the thrown code. No problems since. Good Luck.

Use some anti seize on the 02 sensors. Just don't apply it near the start of the threads.

 

Alright I cleaned them last night and no improvement.....any more ideas????

Thanks again, Ken

 

how's the fuel pressure?

how's the catalytic converter?

 

What kind of sparkplugs did you install in it. If you have anything other then AC Delco Plats gapped at 0.60 That may be your problem Hopefully you did'nt use cheapo wires in it. 4.3 engines run best with Delco plugs...

 

check the plugs see if they are fuel faled on one side or the other if so the injecter is leaking if the plugs look ok they will have a white ash look to them get a spay botel and put water in it run the truck untill its hot and spray all the wiers from top to bottom and the coil any bad spot will show you will be abel to hear it to

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I used Bosch Platnum plugs ..... I will get ac delco ones tonight and try those. I'll check the old ones when I pull them and see if they are fuel fowled as well. If they are is it best to just replace the entire spider system? I did install good wires so I dont think thats it but I will also try the water trick as well.

The Catalytic convertor is good as well as the fuel pressure.

Thanks for the help guys I will post my results.

 

I would also check to make sure that the wires are still pushed onto the terminals on the distributor cap. I just had a problem with my wires (8mo after installation) where they worked off of the terminals on the cap. I used dielectric grease to make sure that they would be easy to pull off in the future as well as to ensure that corrosion would not be a problem. What ended up happening is that the dielectric grease sealed in the air and when pushed on, caused a pressure buildup. The pressure ended up pushing the wires off of the cap terminal causing it to run like ABSOLUTE crap. I had to use an ice pick by slipping it into the boot while I pushed the boot on, allowing the air to escape, then pulled the pick out after the boot clicked on. No problems since.

If the Bosch plugs were just their platinums, then they should be good enough. Not as good as the Delco's IMO, but still decent. The +2/+4 plugs are ABSOLUTE JUNK!!! Just a marketing gimic. The spark will not jump around from electrode to electrode (or multiple electrodes at the same time). It will find the path of least resistance and ALWAYS take that path. Don't buy into the marketing BS, stay away from these plugs.

 

well i'm not a mechanic but this sounds like a possible timing issue. i had a similar problem and it was caused by the timing not advancing properly and ended up replacing the computer of course it wasn't a blazer and much older but i thought i'd throw out the suggestion for ya maybe it gives some one who know better an idea.

 

Make sure you still don't have a vacuum leak. Check the vacuum hoses, mkae sure they are all hooked up and none of them have cracks or holes in them.

Then take your Ignition Control Modual to your nearest autoparts store and get it tested for free.

How often do you replace the gas in your tank? Maybe you have too much water or too much alcohol in the current gas. Did you stop at a different gas station last time? When was the last time you replaced the fuel filter? What grade of gas are you running? Spark plugs and spark plug gap will also contribute to a missfire.