91 lumina hunting idle and dieing

[kippersnack1981]

so if the cat doesnt do its job then what happens? could it be clogged? cause im not trying to save the world with this car. ill cut it off if it gives any problems.

[no2guncntrl]

If the substrate inside the cat has melted due to over
heating from it being either fuel soaked or due to a
misfire, it will eventually clog and no exhaust will pass,
or if it does, very little. That's why using a vacuum
gauge hooked to a manifold vacuum source is so
helpful in diag engine condition. You can also take
it to a half decent exhaust shop and have them
do a back pressure test for very little money.
They can help determine if the cat is clogged.

You can also pull the o2 sensor out and see if the engine
seems to run better. Pulling the o2 out temp lets
the exhaust out of a non clogged hole. You'll set
a code for the o2, but at least you'll be able to
find out hopefully, if the engine can now breath.

[kippersnack1981]

would a clogged cat make it miss? it sounds like an ignition miss. its not a constant miss like a mechanical miss. the fans dont kick on and it idles about 2000 rpm. the icm checked good and so did the coils. new crank sensor, ecm, iac motor, checked the tps, new coolant sensor, new head gaskets because i got it with one blown, new O2 sensor. if i cant get this thing fixed in one more week it will be crushed. it started out as a free car. now i have some dough in it!! PLEASE SOMEONE FIX THIS POS

[no2guncntrl]

I admit I've never seen a clogged cat cause a miss, but
it will surely not let the engine breath which is just a
large air pump. If you have a miss, really the only
way to get to the bottom of the prob or at least a
lot further than a lot of things is to put the engine
on an ign scope. A scope can monitor primary
ign waves, and secondary waves. It cna help
determine if an inj is messing up, if there is high
resistance in either the pri or secondary ign, can
compare companion cylinders for for ign strength
or lack of and can really help get to the nittiy
gritty of what is going on..

Problem is, finding a GOOD shop with a tech that
can read scope patterns as in Raster, Parade and
Superimposed. But if you CAN locate a shop that
do a decent scope setup and readout, it can save
a lot of headaches. The other deal is our system
is a DIS system IE a waste spark system so one
can really only see the ign in Super imposed.

Here is an article that might help you. I realize it's
not specific to your problem at hand, but it might
shed some light upon your dilemma.

http://findarticles.com/p/articles/m...07/ai_n8876015

I still have to get mine started as well. I bought a
factory service manual from eBay for 99 cents
and I'm just waiting for it to arrive to start my
fixin'..

Anyway I hope this helps a bit.

[no2guncntrl]

Whoops. I made a mistake about the Super imposed
pattern being the only pattern. One can see other
patterns if one used an adapter for the scope to
DIS system. I have one for a small scope I have
here at the house.

. I have to use
this adapter for the secondary pattern.

Anyway enough showing my a**. If I can find anything
out, I'll be sure to post so maybe we can all get to
the bottom of these 3.1's running so weird.

[no2guncntrl]

Whoops. I made a mistake about the Super imposed
pattern being the only pattern. One can see other
patterns if one used an adapter for the scope to
DIS system. I have one for a small scope I have
here at the house.

.

http://www.aeswave.com/Products/Product.asp?i=12&ci=3

I have to use
this adapter for the secondary pattern.

Anyway enough showing my a**. If I can find anything
out, I'll be sure to post so maybe we can all get to
the bottom of these 3.1's running so weird.

[kippersnack1981]

i was told that it could be the injectors that are making the car miss. three of them check 12.6 ohms and three check 12.7. they are supposed to check 11.8-12.6. so what do you think?

[kippersnack1981]

i was told by guy A that the ohms is ok. guy B scoped one injector out and said that it was bad. scoped it on a graph thing. he said that it shouldnt spike like that. i found a bad vacuum leak and stopped it. it still misses. ??????????????????????

[no2guncntrl]

If one inj is spiking high, then it has too much resistance
in the circuit or is possibly clogged or partially. You can
do a drop RPM test. Pretty easy. Get it to idle and
then pull each plug wire from the plug for just a couple
of seconds, make it quick. When you pull a wire,
listen for the RPM to drop. If it does that's a good
cylinder and is firing. When you come across one
where you pull the plug wire and you get NO drop
in RPM then you've found your bad cylinder.

I'm not sure on this, but I believe you can so the
same to the inj plugs, but you must be pretty quick.
Get it warned up and idling. Then pull each inj
connector from the inj and see if you get an rpm
drop. If you do, then that's a good cylinder and
is firing. When you come across one where the
RPM doesn't drop, you've found your bad cylinder.

I just received my service manual from a seller
over at eBay. It is massive. At least 3" thick and
appears to have everything about a Lumina in it.



I'll go through it to the troubleshooting misses, etc,
and see what is avail which I'll post you want.

[willlyconchilly]

I'd also check the IAC Valve. It might just be so bad it's dipping down to where things don't function properly.