[2000corolla5speed]

I was wondering if a code scanner would assist in diagnosing a clogged cat. I bought a decent actron scanner that provides live data as you drive. My car is a 2000 CE with about 130K. It bogs and hesitates and a shop told me it is a clogged cat. I tend to agree but would like to confirm before I spend the cash. The entire exhaust appears original. I have already tried a Denso pre cat o2 sensore. I have done NGK plugs regulary. I also cleaned the TBI, MAF and PCV at 90K, and 120K after learning about it on another post. No CEL for the 3+ years I have had the car except when two coils let go at various times. thanks

 

[Fastbird]

Get yourself a cheap $35 exhaust pressure tester. It will screw in where your upstream O2 goes. Just unplug and remove the O2, screw the pressure gauge into the exhaust in it's place, and start the car. Anything over 2 or so PSI isn't normal.

 

[funman1]

^ Only way to test a clogged cat

 

[daver18qc]

There's also the possibility of checking for the "After-Cat O2 sensor" check engine code. If it's not present then it may be something else, but the pressure test is more thorough and won't give false positive if the sensor itself is bad.

 

[2000corolla5speed]

Thanks for taking the time to reply. I do appreciate it. I found a gauge for $43.00. A little steep, but should be a good investment. I had my O2 sensor out recently, so it should be easy to slap the gauge in there and grab a reading. I will post the outcome.







2000 Corolla CE
2000 CRV(family hauler)
1972 Chevelle
1970 Lemans

 

[funman1]

Yeah You can buy it off ebay, use it and then put it right back up on ebay again to minimize the cost.
I call it "Renting from ebay" and I do it all the time for many things
Oddly enough sometimes I will sell a tool back for MORE then I bought it for... hahhaha

 

[2000corolla5speed]

So I ran into a little snag. I pulled the upstream O2 sensor and was all ready to screw in the back pressure gauge, however my car has an O2 sensor that is held in place with two threaded studs. The hole in the pipe is not threaded. Its not like the downstream O2 that threads in. I have a tap and die set, however I do not have the clearance to swing the big handle around to cut threads. Any thoughts? Thanks in advance.

 

[daver18qc]

Just snug the gauge input in there with something that dont burn easily.
There ain't much pressure in there anyway, maybe a couple PSI.
If more than that your catalytic converter is probably plugged hard!

You could also make your own adapter that bolts to the OEM studs and provides you with a threaded hole for the gauge.

 

[2000corolla5speed]

So I went with the suggestion and held the fitting end in the upstream O2 sensor port. Started the car and the gauge did not move off of the peg. I reved the motor and the gauge reamined on the peg, except for a slight flutter when the motor returned to idle. The car was quiet until I removed the probe, so the fitting created a seal. I blew into the hose end and the gauge moved to almost 1 psi, so it appears ok.

I also grabbed the factory O2 off of the shelf and uncrewed the sensor from the flange. I screwed the hose fitting into the flange and bolted it to the manifold. Same result. Gauge only flutters on return to idle.

Am I doing something wrong or is the cat not clogged I guess? thanks

 

[daver18qc]

seems like it's not clogged then?

 

[funman1]

Yep not a clogged cat then...
Check MAP or MAF whichever you have.

 

[2000corolla5speed]

My car has a Mass airflow mounted to the mailbox. Any way to diagnose? I hate to throw parts at the car. Thanks

 

[cj1]

My car has a Mass airflow mounted to the mailbox. Any way to diagnose? I hate to throw parts at the car. Thanks

See if obd2 doesn't have maf data that you can see on your scan tool.

 

[funman1]

An easy way to test is to simply unplug the MAF then and drive around and see if it helps.
WATCH OUT though as you can NOT go over 3000 RPMs with MAF unplugged (It Rev limits out)
so pulling out in front of traffic or trying to get on the freeway is VERY difficult and unsafe!!!

 

[2000corolla5speed]

I found a volunteer test method in the Haynes manual along with a disclaimer that sensor problems can still be present but not detectable by using a voltmeter. I did get a p.o.171 code today, bank 1 too lien, I believe you are onto something with the mass airflow lead. Thanks

 

[glramos]

P0171 On this older models is a intake gasket leak. There is a tsb dB or it
Check if your gasket is made of black rubber , the update it one is silicone orange

 

[funman1]

P0171 On this older models is a intake gasket leak. There is a tsb dB or it
Check if your gasket is made of black rubber , the update it one is silicone orange

Incorrect
You are thinking 9th gen, this does not apply to this engine.

You may well have an intake leak but these are not known for leaking and these don't use a silicone gasket

 

[2000corolla5speed]

I would guess that most readers are growing tired of this post. Forgive me, however I did disconnect the mass airflow. Not much difference. I did check the sensor for resistance using my digital multi meter. With a 20k ohm setting, resistance was 3.15 that is not within the acceptable range. Air temp was about 50 degrees. I guess I will replace. Thanks for the suggestions.

 

[funman1]

I don't think readers are growing tired, we just gave you what we think it is,
so until some parts are replaced or new info comes to light, we just don't have much else to add

 

[finkle1359]

Clean it first. They are very touchy about dirt or dust. Spray some MAF cleaner all over it and see if that helps