Checking catalytic convertor

[junkyardjeff]

Since my recently purchased beater truck has 226,000 miles I want to check the convertor with my infared thermometer so is the exhaust supposed to be colder coming out of the convertor or warmer.

[wayne petty]

out of the converter should be 100F hotter when the throttle is held stable at 2500 rpms for over one minute.. if the converter is farther back.. it may take 2 minutes to properly heat the cat...  1,500 F in.. 1,600 out..  if the fuel control is accurate...  there will be combustion going on inside the cat... as the catalyst metal fragments react with the various gasses in the exhaust flow..


if the beater is a 1996 model or newer.. with a HF 98614 scan tool.. you can look at the secondary oxygen sensors voltages and wave forms in graphing mode...

the O2B1S1 and O2B2S1 sensors should swing from 0.2 volts DC to 0.08 volts DC repeatedly...  at 2500 RPM

the secondary sensors..   O2B1S2 and O2B2S2 sensors should be fairly flat as they monitor the way the cats work..  if the cats get too much fuel .. not enough.. or are worn out...  it will usually set a P0240 code...

warning.. warning.. warning..  a P0420 code does not always mean the cats are not working properly.. only that the exhaust gasses are not within spec...   fuel control or vacuum leaks  are the usual cause of the p0420




let me stop here for a second...

O2B1S1 = oxygen sensor.. bank 1 .. sensor one... upstream of the cat.

O2B2S1 = oxygen sensor   bank 2 .. sensor one   upstream of the cat.

bank one and back two vary from brand to brand..  usually depending where the first cylinder is on the engine.. but not always... these could be on the exhaust manifolds.. or on the head pipes ... but always in front of the cats....

~~~~~~~~~~~~

O2B1S2 =   o2 sensor bank 1 sensor 2...   after the cat..

 O2B2S2  = o2 sensor bank 2 sensor 2...  after the cat

SHRTFTB2S1(%)   this is short term fuel trim bank 2 sensor 1 percentage of offset from designed optimal fuel trim...

here is a snap shot of data from an obd 2 car today from a HF98614

LONGFT1(%)     0.0
SHRTFT2(%)    -2.3
LONGFT2(%)     0.0
MAP(inHg)      8.3
RPM(/min)      713
VSS(mph)         0
SPARKADV(°)     15
IAT(°F)         59
MAF(lb/min)  0.590
TP(%)          0.0
O2S B1S12--B2S12--

O2B1S1(V)    0.150

SHRTFTB1S1(%) -0.8

O2B1S2(V)    0.280


O2B2S1(V)    0.560

SHRTFTB2S1(%) -5.5

O2B2S2(V)    0.310

OBD           OBD2

how about something written on it...
http://www.motor.com/article.asp?article_ID=889


but wait... you only ask about the temps of the cats...

sorry...

[wayne petty]

jeff... ignore all that above...

read this ...

http://www.motor.com/magazine/pdfs/102006_09.pdf

its only 2 pages...

[tomslik]

warning.. warning.. warning..  a P0420 code does not always mean the cats are not working properly.. only that the exhaust gasses are not within spec...   fuel control or vacuum leaks  are the usual cause of the p0420
quote]

not from MY experiance, just the opposite...
BUT if the temp ain't AT LEAST 100 degrees higher coming out (at a fast idle or just coming in from a drive), the converter is dead...
a lot of cats cool off sitting and idling..

P0420/P0430 codes don't mean much as far as that goes but if it's failing NOX,no matter what the temps say,and the egr sys is working and not overheating, it MOST likly needs a cat anyway.

what kinda vehicle?
issues?

[junkyardjeff]

Its a 95 and bought it because I do not ever want a OBD II,its a 95 F150 with a 300 six and if the convertor is bad its going to get hollowed out for now.

[tomslik]

ifit runs ok, don't bother

[junkyardjeff]

It seems like it should have a little more power then it does but it could be the mileage but before I did anything I wanted to check the convertor first due to the high miles and it looks to be the original.

[wayne petty]

with a 95 F150 4.9....

lacking power...  hmm...

have you run a bottle of b 12 chem tool through the fuel system to clean any injector clogs...

area there any air leaks in the duct between the air flow meter and the throttle body?   how about the 1/2 inch hose from the top of the valve cover to the air duct.. is it tightly attached and not cracked or split...

the plastic plug it attaches to that pushes into the valve cover has a calibrated amount of flow into the air inlet duct.. if that is damaged or .. it will leak uncommanded air into the throttle body..  this will lean the motor out as that air is not calculated...

why do i post this.. these are the things i have had to fix on my ISPs 96 E250 4.9... he only had 380K on it now..

if the check engine light is on...  the computer will reduce power... since it is an eec4 system... it has a decent self test...   run the KOEO tests..   run the KOER tests... post what codes you get.... i will try to help...  that year could also have an OBD2 connector under the dash..    do you have only upsteam oxygen sensors in the dual exhaust manifolds...   or do you also have after cat oxygen sensors...

OBD2 cars are a lot easier to diagnose.. as you can actually look at live sensor data...

[junkyardjeff]

It runs ok but I could be used to V8s,this is the first 300 I owned but had a 66 240 years ago that seemed like it would rev quicker then this motor.  I have wanted to run some injector cleaner through it since who knows when the last time it was done and the check engine light is not on,I will look at the items you mentioned tomorrow,its a OBD I and only has one O2 sensor.