• Register Today It's free! This box and some ads will disappear once registered!

^^Searches ExplorerForum.com^^

cat and o2 sensor


eric27

New Member
Joined
August 25, 2010
Messages
34
Reaction score
0
City, State
northwest ohio
Year, Model & Trim Level
93 4.0 xlt
i bought my truckabout a year ago. recently i noticed a "patch" on my cat. im guessing that the insides are gone. my trucks semi loud. will that cause low mpg? also would a bad o2 cause 11 mpg? when my maf is connected i get black sooty smoke and the truck sounds like its under water, mpg goes to bout 8 mpg. unplugged i get the 11 mpg but drivability is way better.....yeah way better unplugged, sounds funny. need help
 


Join the Elite Explorers for $20 per year. Gets rid of the ads! New $5 per month "try out" option.

Explorer Forum has probably saved you that much already, and will continue to save you money as you learn how to diagnose fix problems yourself and learn which modifications work without having to experiment on your own. Elite Explorer members see no advertisements, no banner ads, no double underlined links, can add their own profile photo, upload photo attachments in all forums, and Media Gallery, create and save more private Conversations, and more. Join Today. Your support is greatly appreciated.




eric27

New Member
Joined
August 25, 2010
Messages
34
Reaction score
0
City, State
northwest ohio
Year, Model & Trim Level
93 4.0 xlt
well i guess ill sink more into this truck. itd be the best vehical ive owned if i could get the mpg up. muffler shop said 127$ for the cat and install. i guess its a drop in the bucket compared to the 1300$ invested so far....
 




Maniak

Moderator-Stock 91-94
Staff member
Moderator
Elite Explorer
Joined
February 9, 1999
Messages
12,116
Reaction score
102
City, State
Vail, Arizona
Year, Model & Trim Level
1992 XLT 4x4
If your getting black smoke, your running lots of extra fuel there..

That alone can/will kill a cat (melt and plug)...

The most common reason for black smoke when running is a bad FPR. When it goes bad either the pressure goes way up or the diaphram leaks fuel into the vacuum line which is then pulled into the engine. Check the vacuum line to the Fuel Pressure Regulator.. If there is no fuel there, hook up a fuel pressure tester and see if your fuel is in the low 30's at idle and high 30's when the vacuum line is off.

Also, running that rich can kill/spoil an o2 sensor too..

Do you have a check engine light? If so, grab the codes..

~Mark
 




Iron Weasel

Active Member
Joined
March 22, 2010
Messages
610
Reaction score
1
City, State
Belen, New Mexico
Year, Model & Trim Level
1994 XLT 4x4
The catalytic converter doesn't play much of a part in reducing noise if the exhaust system is in good condition, that's what the muffler is for. Of course, if there is an exhaust leak anywhere in the system prior to the muffler then it will be louder. If you aren't in an area where safety / emission inspections are done, then it's entirely possible that someone gutted the converter rather than replacing it.

The O2 sensor and MAF sensor are another matter. Either of those could cause the low MPG and driveability issues especially if they both happen to be bad at the same time.

The MAF sensor sensor measures the total volume and mass of air flowing into the engine. This value is one of the major factors used by the Powertrain Control Module (PCM) in determining the fuel injection base pulse width and ignition timing advance. So if the MAF is bad or dirty, then it will be giving false readings to the PCM which in turn would cause the injectors to spray an incorrect amount of fuel into the cylinders. If the PCM thinks less air is coming in than really is, it'll dump less fuel into the cylinder and vice versa for more air.

The oxygen sensor detects the presence of oxygen in the exhaust system and produces a variable voltage according to the amount of oxygen present. A rich fuel mixture will result in a low level of oxygen present in the exhaust whereas a lean fuel mixture will result in a high level of oxygen present in the exhaust.

If the MAF is telling the PCM that there is a low air volume entering the engine, then the PCM will lean the mixture out, but then the O2 sensor tells the PCM that the exhaust is rich which is what causes codes to be set and the engine to run weird.

Replace the catalytic converter then check for codes.
 




eric27

New Member
Joined
August 25, 2010
Messages
34
Reaction score
0
City, State
northwest ohio
Year, Model & Trim Level
93 4.0 xlt
okay codes...998, 159. but the only parts thats are not brand new are the drivers side o2, and the ecc. .....i have tinkered with this truck since i got it....i had it running great for about a week, then it went bad again. i have bought new maf, iac, tps, ect, battery, fuel pump and intake lines, fpr, one o2, plugs, wires, coil pack,.....i think im beginning to forget some of them ...there are so many. thats why im not sure what my problems are from.
some more intresting things.....it always reads cool, but feels hot after a min or 2? also only 6 volts on the connector side of iac??? is that normal? thanks for replys....i was starting to feel like it was a lost cause. but i love this truck!!!!!
 




Thread starter Similar threads Forum Replies Date
M Cat Back Exhaust - Stock or Custom? Stock 1991 - 1994 Explorers 1
D muffler or Cat back exhaust kit Stock 1991 - 1994 Explorers 5
W 94 explorer bad cat con symtoms Stock 1991 - 1994 Explorers 1
M cat question Stock 1991 - 1994 Explorers 7
M Gibson 19677 Cat-Back Stock 1991 - 1994 Explorers 4
N Cat converter question Stock 1991 - 1994 Explorers 12
SwaintaN which way does the cat pipe go? Stock 1991 - 1994 Explorers 5
P $60 cat back exhaust Stock 1991 - 1994 Explorers 10
M Y pipe to cat bolts Stock 1991 - 1994 Explorers 15
C Exhaust Question: Y-pipe to CAT connection? Stock 1991 - 1994 Explorers 1
T Where at @ LMC cat? Stock 1991 - 1994 Explorers 7
P cat convertor clogged? 92 explorer 4x4 Stock 1991 - 1994 Explorers 18
B Plugged cat? Stock 1991 - 1994 Explorers 1
T y pipe cat question Stock 1991 - 1994 Explorers 4
A Cat. Converter question Stock 1991 - 1994 Explorers 5
9 new development, cat. converter out. Stock 1991 - 1994 Explorers 6
James909 Importance of cat heat shields Stock 1991 - 1994 Explorers 6
D Cat Converters Stock 1991 - 1994 Explorers 16
jrgaylor Plugged cat? Stock 1991 - 1994 Explorers 5
T cat converter problem? Stock 1991 - 1994 Explorers 5
T cat converter Stock 1991 - 1994 Explorers 13
W Exhaust Leak 2nd Cat / Muffler Pipe Stock 1991 - 1994 Explorers 7
T Exhaust Hardware size for 'Y' pipe to Cat Stock 1991 - 1994 Explorers 0
G Ca. smog fail, new cat Stock 1991 - 1994 Explorers 6
B Could the cat be gone? Stock 1991 - 1994 Explorers 0
U Exhaust leak between muffler and cat. Stock 1991 - 1994 Explorers 8
C cost of cat back exhaust Stock 1991 - 1994 Explorers 2
D how to test the crank sensor Stock 1991 - 1994 Explorers 5
K WWYD- Camshaft synchronizer/position sensor Stock 1991 - 1994 Explorers 11
C MAF Sensor intermittent failure Stock 1991 - 1994 Explorers 2
TDG Early 93 CMP sensor removal Stock 1991 - 1994 Explorers 6
mgmgmg Temp sensor for ecm Stock 1991 - 1994 Explorers 1
S 94 exp 4.o with cam sensor stuck ? Stock 1991 - 1994 Explorers 5
D Solved 1991 Ford Explorer Upstream O2 Sensor Stock 1991 - 1994 Explorers 3
K 4wd vs rwd Front ABS sensor Stock 1991 - 1994 Explorers 2
D air intake temp sensor Stock 1991 - 1994 Explorers 5
Exploring XLT Coolant temperature sensor connected to throttle Stock 1991 - 1994 Explorers 14
K A4LD sensor on drivers side Stock 1991 - 1994 Explorers 4
RustyMacintosh Sensor on the Intake--drivers side--what is it? Stock 1991 - 1994 Explorers 4
massacre ABS Sensor Mounting Point on Spindle Stock 1991 - 1994 Explorers 2
Exploring XLT 1st Gen Abs sensor replacement Stock 1991 - 1994 Explorers 10
A crankshaft sensor location ? Stock 1991 - 1994 Explorers 4
A O2 sensor? Stock 1991 - 1994 Explorers 2
Rhaegal94 Negative battery cable/Engine coolant temp sensor connector Stock 1991 - 1994 Explorers 12
Z MAF sensor troubles. Stock 1991 - 1994 Explorers 13
M Manual transmission nuetral sensor part number? Stock 1991 - 1994 Explorers 3
C UPDATE: ?? trick to accessing 02 sensor connector??? Stock 1991 - 1994 Explorers 3
A Bimetal sensor input hose Stock 1991 - 1994 Explorers 2
C 93 ranger cam sensor issue Stock 1991 - 1994 Explorers 17
N 94 Explorer wont start after changing Crankshaft position sensor Stock 1991 - 1994 Explorers 7

Similar threads

Top