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Discussion Starter · #1 ·
Well I think my CAT is clogged. I have a 4.3 vortec and My trucks acceleration is really bad. It seems to have gotten worse I will try to give it gas and it bogs down bad and starts jerking and chugging then goes back to normal. This happens alot on the highway. My after cat o2 sensor was throwing a code awhile ago so I cut the wires and left the sensor in the exhaust ,but it started running bad. I thought that was the reason ,but now I'm thinking it was trying to tell me the cat was bad. I just replaced the o2 sensor and have run it 70 miles with the codes cleared and nothing has come up again so it seems to be working. I have smelled any rotten eggs from the exhaust or seen any smoke but it does also idle a little funny. Any input would be great. Sorry the post is long it takes a little explaining
 

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Been there Done it
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The easiest way to test it is to unbolt the cat if it's an early Vortec. Some of the later ones have cats welded into the exhaust pipes. What year?
If it's any thing like my 98 and 99's were those bolts can be a real PITA to loosen. I've found that heating them with a torch until they glow red after the heat is removed is the only way to unbolt them w/o breaking them off. If you do break them, drilling them out is terrible because they are hardened and it takes a long time to drill through them.
Might want to a fuel pressure test first. A bad pump could be your problem and both the test and the fix are a lot easier. Just tilt the bed up a couple feet on the drivers side if the pump tests bad. You do need to loosen the bolts on the passengers side.
 

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Discussion Starter · #3 · (Edited)
It's a 2000 and surprisingly some of the exhaust bolts came off easily ,but the o2 sensor was one of the toughest thing to get loose ever. It took kroil and a butane torch to get out. I think I will test the fuel pressure first I'm hoping its the pump.I think I may have gotten codes on my o2 sensor that had to do with the cat and didnt understand them and thought the sensor was bad. Edit: I've have also been having trouble with my gas gauge does a bad pump affect that? Or is that a separate problem I know the float is connected to the pump but do they go bad together?
 

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94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
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1,538 Posts
bad gauge and flaky pump- unbolt bed and jack it up - so you can clean and repair the ground connector that is near the tank. common issue or rot or rust.
 

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94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
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1,538 Posts
single wire from harness running to a loop end bolted to frame.
 

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Discussion Starter · #7 ·
Okay I saw theres also a ground that is on the back of the frame on the drivers side I will look at too.
 

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94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
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1,538 Posts
the one at the rear is for rear lights.
 

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Discussion Starter · #9 ·
Just ran some quick tests and I think my MAF sensor is the culprit. I unplugged and the engine slowed down and then started idling normally again. Seems like it runs worse with it plugged in.
I will try cleaning it but may replace it if that doesnt work. I'll try to give a update after driving it for awhile.
 

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Glad to hear you got it fixed and thanks for letting us know the cure. Did it give any codes while acting up?
 
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