96 Tracker P0420

[gorkyb]

No symptoms, P0420 simply came on.

Welded a brand new CAT less than 3000 miles ago, grant it, I did not pay much for the CAT but still, I doubt it's melted already.

Still I did the following just to be sure: from page http://www.fixkick.com/sensors/tests/cat...blockedCat , I duplicated the following step since it was the easiest for me at the time (super cold up here and getting dark very early still):

Quote:
"To check for a restriction in the exhaust, attach a vacuum gauge to the intake manifold and run the engine at approx. 2000RPM, observe the vacuum gauge as the engine is allowed to quickly decelerate.

If the exhaust is FREE of restriction, the vacuum gauge reading will increase immediately upon closing of the throttle, then settle down to a normal reading. If there IS a restriction, the needle of the gauge WILL NOT show an increase." (due to huge backpressure at the exhaust ports)"

It does pass the test, vacuum needle jumps right back up as soon as I let the gas cable go. Engine feels normal, no evident loss of power. While engine at idle (800 rpm's) and in neutral, I did feel a couple of hiccups, nothing major though, but I did feel them. They happened a couple of times, no more.

Next, I will be taking out spark plugs to check for wetness (leaky injector?) Car was running rich in the past (before I did all the engine work to it) so I reused the spark plugs because they were fairly new still, I cleaned them the best I could and I am using them again. I have a brand new set of NGK's which I can put in if need be.

Fuel pressure at idle according to liquid filled gauge at fuel rail is 29 psi.

Some guidance please?

[fixkick]

420s are a pain, the rear 02 thinks the Cat is dead or slow or lazy.
1/2 the time the ECU is wrong here. (or the 02 rear is just bad)
the key to getting good 420s. (besides, replacing cat) is to get engine running in closed loop at idle. and at fast flat steady cruise. if it does that , the cat will run warm and wake up and pass 420s (with deity blessings)
your cat is not melted, im sure.
ran rich before, this can make the cat , full of fuel and you need to run it at cruise and get it hot as a pistol and it will back dry and wake up. Id did that on one full of raw oil.
the 96 kick ECU will suspend 420 test if it think the front sensor reads bad, but it can be fooled, and yours thinks the front is ok
but why is the LTFT at -15% (i think that means the ECU is subtracting fuel due to 15% too rich.
i dont thing the MAF is too high. by 15%
so where is the extra fuel coming from , but the way 15% is not bad, its just tad high. -5% is very good. the oxy sensor front sees the is rich and the system corrects it with -15% adjustments. i only mention it because, there may be a leaking injectors, a dribbler. and will make idle bounce from time to time. as that cylinder fouls and clears.

id try injector cleaner. Chevron is the best, i dont like additives but this one is only what's in Chevron fuel already, lots of benzine. a vary powerful solvent.
use bottle instructions for quantity
is your 02 a fresh sensor?
when i got my 04 , some PO put in some weird additive and sparks and o2s were all purple in color, so i ditched them....(front only)
sure 420s can be a dead rear 02, the ecu expect a flat line, from it , and then bumps. as the ECU tries to keep the CAT fully hot.
the ECU works hard to keep the CAT alive and lit off an the 420s checks that that happens, and the complex wave form from that 02 rear. fooling it is very hard.
most folks ignore 420s, and drive.

i looked at your scan it looks great. just tiny drop in LTFT (neg)
minor leaking injectors will show up at idle. mostly.
you will hear a misfire.
im sure Techron will clean clean them. if the gods are willing,


o2 sensors not dead, are impossible to test. they can and do get poisoned and then are offset. they lie. they swing and look perfect but lie. (offset biased)

hope my ideas , help in some small way, and good luck to you. are you in federal smog zone (test)

[gorkyb]

In the last 5 years that I've had my cars inspected all they do is to hook up the scanner to the OBDII port. Then they inspect for conditions of the brakes and tires, lights and blinkers, that's it.

I will try Chevron injector cleaner, can't hurt. That small hiccup I mentioned before that comes from time to time could be a leaky injector, I think.

I've had LTFT at close to -5% in the past.

Both, front and back O2 sensors are new. Bosch with pre-wired connector.

Car reaches closed loop quickly after start up. Drove it to work today, ran great, no issues that I could notice. (18 mile ride one way)

My brother is coming to visit me from South America next month, I want to get the Tracker running nicely so I can take him trailing upstate (3 to 4 hr. drive to the off-road park), mild trailing road I am thinking, nothing crazy. I'm planning on driving the Wrangler at the same time, I would just hate to have to tow the Tracker back to Long Island after the long drive. =/

I am putting the stock (uncut) springs back on this weekend and getting a decent set of used 235/75/15's or something close to that.

[fixkick]

yes, they can pass any car, with OBD2, in many states, with CEL out, and scans clear and all monitors run out (1 can be late)
then the gas cap seal is tested, (leak down test)

420s means only lazy cat, and is not going to fail or cause issues. in fact, it might get better the more you drive.
if no feds biting at heals. 420s is no problem..... in 1995 there was no 420s. and the engine ran perfectly.

if the car runs great, good mpg, no misfire, bogging or overheating (its in closed loop, so all is good)
its ready to go.
HAVE FUN !!!!!

i just keep faith on 420s, it can cure itself..
i dont think the non TWC cat (if that is what it is) can do this. three way cat. ive seen 2way cats pass 420s. (a great topic in own rights)

[gorkyb]

I erased the code twice, it keeps coming back. All systems seem to be working ok, car has nice power, no hesitations or anything. Bought the injector cleaner yesterday, waiting for the weekend when I have to refill the tank to put it in.

Thinking about the exhaust work I did, when I welded the new CAT in, if I did not weld it completely shut and I left a small leak either before or after the CAT, would that throw off that downstream o2 sensor?

My inspection is due at the end of May so I have 2-1/2 months to figure this out.

[fixkick]

the cat is weak or has the wrong cat.
the cat must be lit off.
lit off happens 2 ways.
cat must be close to the exhaust header, and the ecu sends it extra wasted fuel to do that, (that is why 96 has tad lower mpg than 1995 this waste)
sure exhaust leaks of any kind will kill the 02, (im sure non of this is your problem)
just leaks.

outside air is 20% oxygen.
if you get even 1% of that , in to there, the 02 slams lean.

420 are harmless. its just a code to say the cat is lazy, at the least or missing. or dead. nothing more.


all exhausts systems go positive and negative pressure, at each and every put.
when negative,it will suck in air.
both ends off the cat must be air leak free,

this is a real pressure plot . no leaks allowed,

---

front leaks, cause EFI to waste huge fuel.
rear leaks cause fibbing 420s. just one tiny crack and bam 420s and is a lie,. the new cat works only the test fails.

[gorkyb]

So after I erased the last P0420 it hasn't come back yet, but checking the scanner I found P0133 pending there. I haven't reset or touched anything at this point. Car continues to run and drive normally so far.

[fixkick]

133 is front sensor slow.
the ECU can suspend the 420 monitor if it thinks the front sensor is bad, seen this many times... kinda smart for a suzuki.

if you look at monitor status, you may see is pending all the time, (frozen)

old a new sensor is slow.

got air leaks in front of cat? or the infamous exhaust header #4 down tube cracked?
non of this is serious yet. (running wise )

[gorkyb]

133 is front sensor slow.
the ECU can suspend the 420 monitor if it thinks the front sensor is bad, seen this many times... kinda smart for a suzuki.

if you look at monitor status, you may see is pending all the time, (frozen) <--- true, that code is stuck there, not moving

old a new sensor is slow. <--- sorry, not sure what you mean

got air leaks in front of cat? or the infamous exhaust header #4 down tube cracked? <--- tube #4 weld is still holding for now, I think there may be a whissing sound coming from the donut gasket area where collector and the downpipe connect, but with all the engine noise is very hard to point out, I will try a rag on tail pipe to increase back pressure and look for leaks on the whole exhaust system

non of this is serious yet. (running wise )

A leak in the exhaust system could also explain why my LTFT is a little higher right?

[fixkick]

sorry!, the DTC for 133 means the oxy sensor is slow. B1S1 slow. It's slow for a reason. and not for too old.
remember that the 02 sensor swings. and if slow , there are problems.
yours is new, so why is it slow?
heater inside dead? (nah, there is a DTC for that)
air leaks.? near it? is my 1st guess, if wrong, it a fueling issue.. (dribbling injector ?)

TOOLS(free)
use a rubber hose held to ear. to find exh. leaks, (and rag trick is brilliant!!!)
i make a hose and duct tape (1million uses now, lol) to a 2 foot stick end (pipe or metal rod) and hold the rod in one hand and tube to an ear,
and can find leaks and not get burned on the 2000f exhaust.

on the 1996 and 1997, i have seen the 420s monitors suspended for ever. due to 133 or any other front sensor errors. its smart this way. (makes you find root cause it does)

the slow 133 might mean , its going in to closed loop then bouncing out, oddly.??

I'd put on after market headers if not living in CALIF. or states that run CALIF smog rules. NY is one that does i think?????? IIRC?
In calif. they do a visual ,and hark, omg a header, is this header on the EO list? they say and look, engineering order list.
that means the calif certified aftermarket list,

but here is some nice headers. that would not leak ever.
i like them all but the Thorely has a poor EGR port, (can change at drop of hat , any time in future)

i think Calmini wins the toss... in most cases.
but in every case , welding fitting can be required.

http://www.fixkick.com/buy-parts.html#misc-mans


stock man is
14111-58BV0
$338 at suzuki
the donut gasket must not leak.