Cat. converter test

[philipk65]

How can I test my cat. converter to see if it work properly. Any suggestions would be greatly apperciated!

[MT-2500]

What year and engine?

A fast test on cat plugged up is a vacuum gauge at idle and 2K rpm.
If vacuum drops lower at 2K you are looking at exhaust blockage.

Newer engines the front and rear 02 sensor readings are used to check cats.

Are you getting any codes or what is it doing or not doing?
MT

[philipk65]

It's '91 s-10 4.3 L and there are no codes.

[MT-2500]

Hook up the vacuum gauge and give us the engine vacuum readings at idel and at 2K and at #K.

[philipk65]

I checked the vacuum for the cat. converter it was as follows-
idle - 5 hg then when I reved it to 2k it dropped just a hair for a milli-second then went up to 5 hg and stayed right there at 5 hg at 3k.


I took an infrared temp gun to the inlet and outlet of the cat.

Inlet temp 135 degrees

Outlet temp. 175 degrees

Does this sound like the cat. is working? Thanks!

[MT-2500]

Originally Posted by philipk65

I checked the vacuum for the cat. converter it was as follows-
idle - 5 hg then when I reved it to 2k it dropped just a hair for a milli-second then went up to 5 hg and stayed right there at 5 hg at 3k.


I took an infrared temp gun to the inlet and outlet of the cat.

Inlet temp 135 degrees

Outlet temp. 175 degrees

Does this sound like the cat. is working? Thanks!

Your vacuum readings are way low.
A good running engine should have 18 -20 in hg vacuum.
Anythng under 17 is late timing or timing chain or engine running problem.

Start with a base timing check.


Cat tempt should be up over 500 degrees.

[philipk65]

I read the gauge wrong. The vacuum reading were 20 hg at idle, then at 2k went down for a split second the went to 20 hg, and at 3k stayed at 20 hg.

Does that reading going down a hair for a split second mean anything? It didn't do it from 2k to 3k.

If the cat is plugged should the temps be hotter or cooler than 500 degrees

[MT-2500]

Originally Posted by philipk65

I read the gauge wrong. The vacuum reading were 20 hg at idle, then at 2k went down for a split second the went to 20 hg, and at 3k stayed at 20 hg.

Does that reading going down a hair for a split second mean anything? It didn't do it from 2k to 3k.

If the cat is plugged should the temps be hotter or cooler than 500 degrees

That is better.
Yes vacuum will drop when you give it gas. That is normal operation.
If vacuum does not drop at 2-3K range cat is not stopped up.
Fuel mix and engine running has a lot to do with cat temptures.
As as you do not have a hot spot in exhaust it is good.
They may be a little hotter in front than back if working good.
To tell if a cat is working you would need a exhaust sniffer or a 02 sensor in front of and behind cat.
MT

[philipk65]

MT-2500, I grounded the A and B terminal I got trouble code 42 (EST). I says in the manual to check timing a 2k grounded and ungrounded. Will I hurt anything grounding and ungrounding the terminal with the motor running while checking the timing? Then it says to set the"base timing". Is this the same as setting "ignition timing" when you disconnect the wire under the dash and check and set the timing that way?

[MT-2500]

Originally Posted by philipk65

MT-2500, I grounded the A and B terminal I got trouble code 42 (EST). I says in the manual to check timing a 2k grounded and ungrounded. Will I hurt anything grounding and ungrounding the terminal with the motor running while checking the timing? Then it says to set the"base timing". Is this the same as setting "ignition timing" when you disconnect the wire under the dash and check and set the timing that way?

It will not hurt it.
Go ahead and set the base timing that way and see what it does.
And then disconnect the base time wire under dash and recheck.
Should be the same either way.
The run the repair flow chart for code 42.
MT

[philipk65]

Where can I get the repair flow chart for code 42?

[MT-2500]

Originally Posted by philipk65

Where can I get the repair flow chart for code 42?

A good repair manual or a all data sub. or the auto zone web link may have some inf on it.
http://www.alldata.com/products/diy/index.html

You also may have a bad ign module.
Good luck
MT

[philipk65]

I went through the EGR system check flow chart. Everything was checking out A O.K. but when I got the the part in the chart (at bottom left) "under light acceleration observe vac gage" I hooked in the EGR vac line, it is suppose to be under 10 ''. I got 0?! That was the last step, up until then everything was checking out fine.
Did I do some wrong?

[MT-2500]

Originally Posted by philipk65

I went through the EGR system check flow chart. Everything was checking out A O.K. but when I got the the part in the chart (at bottom left) "under light acceleration observe vac gage" I hooked in the EGR vac line, it is suppose to be under 10 ''. I got 0?! That was the last step, up until then everything was checking out fine.
Did I do some wrong?

I thought you hade a code 42?
How did you get on a egr valve check?

[philipk65]

I did have a code 42. I reset it and drove to and from work (24 miles) and it rechecked for code and now I have none.

I found an EGR flow chart online.