Anyone have remove cat convetor?

[deeznutts77]

i hollowed out mine and had no codes or running issues. put header on and triped 0400 so thought it was cat ,got one now, still 0400in. pi$$in me off, but 25-27 mpgs and i drive it hard but i love the little thing.

[TRAVIS75]

Recently got my 93 kick 4dr a/t 16v running again. Not before spending 2 months locating a exhaust man, replacing a stuck injector, drilling out melted cat, and finally having the ecu rebuilt. I had read what JTGH had posted when I was having problems. Prior to fixing all my problems, I was getting about 15 mpg, thats what it was getting when I bought it at our auction at our salvage yard. Never got any better or worse until the afore mentioned problems occured. Since I've had the computer rebuilt, it now gets about 22 mpg. I've not yet replaced the cat, and not sure what effect it has had on the egr. So all I can say is that the combo of drilling out the cat and having the computer rebuilt, is that I've gained 7mpg. I have to admit that it now lacks the take off power it once had, especially in higher elevations.

[relicduke]

22 mpg?isn't that pretty sad for that engine/car size? If I was gonna burn that much gas I'd want more noise/power/fun doin' it,like a 350 4bbl Chevie

[tusong200]

Yeah, 22mpg seems really low. Hopefully you'll get some other problem sorted out and get the mpg's back up to where they should be, at least the high 20's.

[TRAVIS75]

so if i replace the cat, can anyone tell me, did I mess up the egr and should I just replace it too. I'm sure that I can get the mileage back up to 26 or better, and it would be nice if I could regain that power and torque at the higher elevations again since I may be using this as my hunting vehicle.

[jtgh]

travis,
what's not stock (oem orig. on car engine)?

caT , (check) what else?

22mpg , in town, with heavy foot is easy to hit. (USA gallons not imperial canadian)
ive never got worse than 25 on my 8v in town.
and never worse than 28 on my 16v in town.

now that my egr works i get over 30 in town. on my 16v.
the 16v has sequential injection system and works better in town than any 8v TBI.

there are many things that can mess up MPG .
besides dragging brakes and what not. (tune up parts)
16v only:
ECU is in Limphome mode. ( i call this the chevy blazer effect , wow) "relicduke !"

fuel pressure way over spec, (bent return line, bad regulator bad vacuum source to same)

leaking injectors.
bad ECU.
retarted ignition timing most likely caused by next line.
slipped timing belt.
stripped crank cog , key way behind crank pulley. (very common)

Bad MAF , reads high full time.

pre 96's are hard to tune.
by tune? , i mean,

look at data stream and watch how Closed loop works. !!! and short term fuel trim !!!
we can do that, sadly. NO OBD1 scan tools, over the counter.

bad cat , clogged cat, rodded out (drilled) cat.
bad EGR system.

Bad motor ( for all the long list of reasons. but simply , it wont pump air , or dead /weak cylinders)
3 cylinders pulling 1 dead one, is very bad.


the book shows , doing the live EGR test first step.

the egr either works or it dont.

94+ requires jack stand test
93 minus , can be tested in drive way , wheels on ground for EGR test.


the EGR will over flow the EGR circuit if the exhaust back pressure is too low.
how ever my 96 , still gets good MPG with a dead EGR. (got 28)
the older cars , can do horrible things when the EGR is bad.
Limp home , really stinks if ECU decides to do that.

we can test each part, but not the MAF, (im working on a way now)
the maf can be tested on car if it is good.
if it is bad, it is very hard to test car , cuz motor runs so bad.

now that we have seen so many bad cranks, it is best to inspect it , at tbelt change.

[TRAVIS75]

Well after spending 360 dollars on labor and having computer rebuilt, it better not be in limphome mode again, i'm sure its not, when it was i had gas running out the exhaust-wouldn't idle smoothly until reaching higher rpms etc. Fuel pressure I don't have a clue, i'm a backyard mechanic, and truthfully that statement may offend a true backyard mechanic since I'd barely qualify to call myself that. It clearly has a bad cat, as I've drilled it out, which of course leads to lack of back pressure, according to the mechanic that looked at this, I did have an injector stuck wide open, which has been replaced, and as far as the engine being bad, mechanic did compression test and all cylinders tested in the 154 to 160 range. At this point I'm ready to just replace cat, and egr cuz frankly I don't think i could fumble my way through testing it. I did swap a maf off of another very driveable and seemingly perfectly running zuke as a test, no change after 200 miles.

[jtgh]

oh, luck to have a spare, maf, me jealous.
93-16v

leaking injector is the worst of the worst.
leaking fuel proved that.
it destroyed the cat.

id recommend a new cat and o2 sensor and cross fingers.
your compression is a tiny bit low but ok.
and you qualify for being a BYmech, you did great !

if the egr main will stall the motor, just leave it be.
drive it and see if 51 clears.

EGR monitor needs a good running motor first.
on yours the egr is tested using the egr thermo sensor and is kinda simple.
The ECU opens the EGR valve and if this sensor sees HOTTER. it passes the test.
brutal simple.

i think getting you back to closed loop is tops
then we address any dtc codes that come up.

[shackwrrr]

jerry another thing and to answer deeznutts77 in obd 2 if the egr fails the only thing the computer does is turn it off. thats it other than putting a little more fuel because now there is more room in the combustion chamber for it.

[jtgh]

on the 96+ it runs the valves hotter.
it may give more power at wide open throttle, but part throttle is your foot , as always.

on the newer cars, the egr is used for cooling the valves while crusing and not using wideopen throttle.
it helps in other ways too.
I do not believe the EGR is ever shut down[note1] ( first off, the EPA would not allow that)
if you have pending codes 400 or actual code 400s,
the monitor gives up ( its a one shot anyway after 240 seconds of run time , 2 tests)

but the EGR , software, EFI part, commands the valve open and EGR will flow.
using the same logic as always, cruising, hot.
but.
if the EGR components are bad then
you get :
no flow
too much
too little.

the ecu opens the valve and hopes the HARDWARE , does its job right.
in 1999 , this all changed.

in 1999 the ecu takes over all rules and controls from the HARDWARE and just
modulates the EGR via the motor inside the EGR.
100% software , rates, flows and logic.
a vast difference.

that is all i know about egr on the obd2 side.


if you do have a CAT , an the #4 exh tube hole is not blocked , then
we can make your EGR work.
I promise ,we can.

many folks here have tried, low flow cats on 96 with great success.
if the stall test passes, then go to the live jack stand test.
just do it in neutral by the book. (have book will share)

note1: ( imagine a computer chip AND gate for the below, cuz that is what it is )
EGR is shut down when:
cold motor.
idling
W.O.T. (NO EGR at WOT EVER )
not moving.


when EGR is gated on via the front EGR VSV (ecu does that)
EGR is controlled by:
ported vacuum .
exhaust back pressure. (mod valve)
condition of all valves and pipes ( no blockages or sticking valves)
on 96 , there are 2 VSV valves that must not be bad. ( 1 valve 95 and older and even older a water temp valve)
The ECU does not modulate flow, as some books say, no, it does not 98 and older.
ECU turns it on ,or it turns it off, thats called GATing.


96 trips EGR fails easier, but is far easier to diagnose. ( and far easier to clean due to no tiny hidden EGR injection holes case in manifold)

just clean the main egr. valve so it snaps back close each time you ,open it with fingers on diaphragm.
then clean the right side EGR SST tube ,it likes to neck down in the very center of tube (cold spot)
then clean the TB injector port #4 with 9mm pistol brush.
then clean the 90 port on the right side of plenum.

check all coils for non open conditions VSV.
check that they all click.
and if it still fails.
test each vsv by hand with a vacuum tool. I have the full written test on both valves.

it can be made to run.
millions running , ok and passing state smog every 2 years.