Catalytic converter clogged?

95BLAZERRICH

MEMBER
1995 CHEVROLET BLAZER
6 CYL
4WD
AUTOMATIC
188,000 MILES

I have a 95 chevy blazer 4.3 engine code W I have replaced the fuel pump, the cat, and the muffler I have checked for vacuum leaks and done a smke test on the vacuum hoses. The truck losses all vacuum under accelleration. With a vacuum gauge it has 24 inches of vacuum at idle and under a load going up a hill it will drop to 5 inches. I do not know were else to look for this problem can you help please. Thank you Richard Mitchell

7 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Check the exhaust system for an excessive backpressure-could be a problem with the catalytic converter. This guide can help us find out

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please run down this guide and report back.

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Tuesday, May 26th, 2020 AT 11:46 AM

95BLAZERRICH

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2 POSTS

Thank you. From what the vacuum gauge is showing the motor is healthy. At idle wich is at 700 rpm I have a steady 22 inches of vacuum. Open to close it drops to about 4 inches and jumps back to about 25 inches. What is happening is under a load climing a long hill at 60 mph the vacuum will drop off and the A/C will blow from the defrosters and the floor instead of the vents. As soon as the hill is cleared the A/C comes back to the vents. I was driving the truck and out of no were it had a rough idle for a minute and all of this started. Can a bad egr valve cause this? The truck has also had a slight drop in performance and fuel milage. Thank you for all the help

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Tuesday, May 26th, 2020 AT 11:46 AM

BLK93NOTCH

MEMBER
3 POSTS
1994 CHEVROLET BLAZER
6 CYL
4WD
AUTOMATIC
190,000 MILES

Im working on my sister 94 s10 blazer 4wd amd its missing at idle. It smooths out after giving it gas. I have replaced cap rotor wires plugs injector, pressure regulator and have taken the cat off. I thought the cat was plugged and it eneded up not the problem. I am getting a very strong fuel smell but I figure that it is from having no cat. I am stumped right now. It starts fine but misses at idle. If I hold gas it smoothes out but then it smells like raw gas. Any help would be great. Also no codes at all.

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Thursday, September 10th, 2020 AT 12:53 PM (Merged)

RASMATAZ

MECHANIC
75,992 POSTS

You might want to clean out the idle air control valve for a start

A rough idle could be a large vacuum leak can lean the air/fuel mixture out to such an extent that an engine will not idle at all. An EGR valve that is stuck open at idle can have the same effect as a vacuum leak. So too can a loose positive crankcase ventilation (PCV) hose, a leaky PCV valve or the wrong PCV valve (one that flows too much air for the application). If somebody replaced the PCV valve recently, they may have installed the wrong PCV valve. The rough idle in all of these cases is caused by "lean misfire." The fuel mixture is too lean to ignite reliably so it often misfires and fails to ignite at all. Lean misfire will show up as elevated hydrocarbon (HC) readings in the exhaust, which may be enough to cause a vehicle to fail an emissions test

Misfiring can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

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Thursday, September 10th, 2020 AT 12:53 PM (Merged)

BLK93NOTCH