LT1 running like A**

[RCcola55]

lately my caprice has been running really crappy. It has no balls until 2500 rpm, runs super rich, and has a really rough idle but no check engine light. It has done this before and one of the o2 sensors was to blame. I just wanna see if there could be anything else before i go replacing the other one. Fred???

[agjohn02]

make sure the o2 sensors have good grounds. the little clip on grounds dont stay grounded very well. i think i put worm clamps on mine.

[Sharpe]

I can scan it for you sometime, maybe tomorow evening.

[BMFScout]

what's it do before the opti-spark dies?

[agjohn02]

what's it do before the opti-spark dies?


why is this everyone's first guess at any problem with an LT1?

"she's running hot."

"uh oh, the opti's about to crap out on you."

[BMFScout]

Didn't yours die? Aren't they known to be problematic and don't throw the engine light like an O2 sensor probably would.

[agjohn02]

Didn't yours die? Aren't they known to be problematic and don't throw the engine light like an O2 sensor probably would.


i dont know if mine went out or not. i havent had time to look at it. yes its a problem, but really only when the pump goes out and dumps water on it from what i understand. the opti is a pretty sudden failure. like getting water in your dizzy. doesnt make it run bad, just makes it not run.

[sasquatch]

sometimes o2 sensor codes don't give a check engine light. sharpes scanner should tell you if either of them is bad. if they don't cost an arm and a leg, I'd replace both so both cylinder banks will be even.

[Fredo]

No, the optispark dying isn't a sudden failure. I've known more than a few to progressively get worse. A lot of times they run just fine unless it's a cool humid day, or a really hot humid day. They become very tempermental. It's mainly on the 92-94 non-vented optisparks though. The 95-97s don't seem to be as problematic as the non-vents. If I remember correctly, the 94 Caprice's and Impala's got the vented before the 95 model year. Suprising it got something before the corvette, but I think it had to do with the caprice police package.

Ryan, what I would do is if Sharpe actually has a realtime scantool and not a code reader, hook it up, see what the o2 voltages are and see where the fuel trim blm's are at. They should be somewhere around 128. If there is a large difference from the left bank to the right (15 or so) then you might have a bad o2, or a clogged fuel filter, bad injector, clogged catalytic converter, bad MAF sensonr, throttle position sensor, water in the fuel, or a bad opti.

[agjohn02]

it took you long enough to search ls1tech for that, sheesh:flipoff2:

[sasquatch]

Ryan, what I would do is if Sharpe actually has a realtime scantool and not a code reader, hook it up, see what the o2 voltages are and see where the fuel trim blm's are at. They should be somewhere around 128. If there is a large difference from the left bank to the right (15 or so) then you might have a bad o2, or a clogged fuel filter, bad injector, clogged catalytic converter, bad MAF sensonr, throttle position sensor, water in the fuel, or a bad opti.

its just a code reader i think. can't you just use a meter to read the ohms at the plug? i doubt it is as precise as your method but it should work

[agjohn02]

bad injectors do not make it run crappy. i had two that were frozen when i first got the scout running. other than power and exhaust note, i couldnt tell a difference. i towed my boat and all my crap to south texas before i figured out what the problem was. i used a stethoscope to figure out which ones werent working, tapped on them with a screwdriver and they broke loose and have worked fine ever since.


does the car run better under light throttle than it does if you get on it?

[Fredo]

it took you long enough to search ls1tech for that, sheesh:flipoff2:

Yep....you got me.....that's exactly what I did :flipoff2:

[Fredo]

bad injectors do not make it run crappy. i had two that were frozen when i first got the scout running. other than power and exhaust note, i couldnt tell a difference. i towed my boat and all my crap to south texas before i figured out what the problem was. i used a stethoscope to figure out which ones werent working, tapped on them with a screwdriver and they broke loose and have worked fine ever since.


does the car run better under light throttle than it does if you get on it?

Yeah, that is true. I've heard for 5.3's being notorious for this after sitting up for awhile. Just store that one away for later John.

[agjohn02]

my injectors havent been sitting very long;)

[Sharpe]

My thingy is primarily a code reader but it can display a dynamic reading of a bunch of engine sensor stuff that I dont understand, so it's probably worth a try.

[Fredo]

If it's showing realtime sensor data, you should be good.

[TxCruzr]

bad injectors do not make it run crappy. i had two that were frozen when i first got the scout running. other than power and exhaust note, i couldnt tell a difference. i towed my boat and all my crap to south texas before i figured out what the problem was. i used a stethoscope to figure out which ones werent working, tapped on them with a screwdriver and they broke loose and have worked fine ever since.


does the car run better under light throttle than it does if you get on it?


I don't know about that. I rode with a friend right after he got done putting a lt1 in his cruiser and it would run like poo at low rpms and even died a few times at idle. Ran fine at higher rpms thought. Ended up being 2 of the injectors.

[Fredo]

I guess it could be kinda like if you have bad or missing plugs/wires. Depending on which cylinders aren't firing and their location in the firing order, it might not run that bad. Also, if the injector is stuck, it could still be leaking slightly allowing that cylinder to fire, but run lean.

[RCcola55]

its runs pretty good at high rpms but still not like it used to.

[agjohn02]

I guess it could be kinda like if you have bad or missing plugs/wires. Depending on which cylinders aren't firing and their location in the firing order, it might not run that bad. Also, if the injector is stuck, it could still be leaking slightly allowing that cylinder to fire, but run lean.


exactly, i just had the correct two not working at all. i should have said "do not always make it run crappy". it's a little different than plugs and wires missing. if it were still pumping fuel and not getting spark the other cylinders would go super lean trying to compensate. if you are just pumping clean air through, the other cylinders fatten up trying to compensate.

[agjohn02]

its runs pretty good at high rpms but still not like it used to.


not necessarily at high rpms. when my grounds get bad, anything other than slight throttle makes it cough and sputter, but i can cruise around easy and it runs fine.


you might want to get a stethoscope and check the injectors. i would say use a noid light but that doesnt tell you if the injector is stuck. the only way to do that is listen. if you dont want to buy one, ive got one you can borrow.

[RCcola55]

left bank o2 sensor, figured it out tonight thanks to sharpe. fuel trim difference was 126-140 (right to left). Also decided that i want to put in a 180* thermostat, so add that to the list on the programming fred and delete the damn o2 sensors so i dont have to change another one!

[robertf03]

you sure its o2 and not injectors, pistons/engine/exhaust leak?

[RCcola55]

yep im sure... code 44 i believe


edit: im dumb, replaced the o2 sensor, no codes now but still runs ****ty