Sensor Problems

Ok guys, I have a good performance related issue for ya. I have a 91 z28 tpi, 305, with flowmasters and no cats. I found out recently that my plugs keep fouling out because of having no cats with the stock O2 sensor (how the dealer put it). One option thats been given to me is to put high flow cats on the car, another that I haven't been able to find much info on is if there would be the option to put a performance O2 sensor on. Are there such things? Would an aftermarket O2 help my problem any? I'm also a little confused as to what the difference is between the MAF and the O2 sensor. Any help is greatly appreciated.

ive heard that if you move the o2 sensors further downstream in the exhaust (away from engine) that it helps to fool the computer into changing the fuel ratios because the concentrations of the gases change as they move through the exhaust tubing. of course ive never tried it or anything but maybe some one here will confirm and then maybe you can use that to remedy your situation. also, i know that ive never seen "performance" o2 sensors, i figure an o2 sensor is an o2 sensor. what you can to however is pull out the stock ones and try to open the slits in the sensor end (i think its open). supposedly that will allow more gas to flow through and will help to fool the comp also.

O2 sensor reads exhaust gases to adjust the mixture for lean and rich. MAF (mass air flow) measures airflow coming into the engine so the ecm can confensate for load conditions. it's a wire that heats up to about 200 degrees celsius, and the ecm monitors how much current it takes to keep the wire at a constant temp. more airflow, the cooler the wire goes and the more current it takes to keep the wire hot etc.

the "performance" 02 sensor is actually a fake O2 sensor, it plugs into the harness where the O2 sensor goes, but dosnt actually go inside the exhaust stream, it sends a constant 14.7:1 ratio to the engine i beleive, perhaps a bit richer, say 13:1 or so. so you would have to plug those in and seal off the holes where they originally went. as far as moving them down the exhaust, wont work, still screw up your plugs, i would recomend the high flow cats, random technology makes them, and they work great, have one on my RS, whats left of her anyway lol.

the same thing was happening with my 93 camaro. i had the cat cut off about a year ago and about a month later it started sputtering and losing RPM while accelerating.. i didnt have the money to get it fixed, so i left it in the driveway for about a week or so and havent had a problem yet.. no idea what happened, but it runs great now..

the spark plug fairy came by ;)

Ive had both cats off my 91' Z28 L98 and Ive never had a problem with my plugs fouling? The O2 sensor on these cars is way before the cats so I dont see how the cat could change your O2 sensor readings?

By performance O2 sensor, he may have meant you could get a Wideband O2 sensor? Just a thought

is the l98 running a carb? maybe the tpi has something to do with it i just dont know. i dont think the exhaust would get in the way either. all that i could find out is to fix the problem i could get high flow cats and that supposedly would solve it. ive seen a heated o2 sensor on the market. all i know is im blowing carbon out the back and the buildup is also fouling my plugs. gonna research a little more here..

No, the L98 is TPI too.. maybe you just have a bad O2 sensor? is your engine light coming on?

it did a few times before i had it in the shop. i just had it tuned so im guessing they would have known if the o2 sensor was bad but then again maybe im an idiot for that hah.

Try replacin the O2 sensor.. Sometimes those dealer mechanics like ta say things like that ta try make a few part sales.. That y-pipe with the dual cats is a very expensive part

yeah im kind of ruling that out as an option id try to trick the damn thing before i put that into it.

yeah, if the check engine light isnt on at the time, they wouldnt check it. so dont expect anything from them beyond the basics. if your fouling plugs its running rich, O2 sensor tells the engine what mixture to run. so thats where i would start.

i've cut the cat off TBI camaro's before, and no problems with fouled plugs. chances are the cat you took off wasn't doing anything anyways, there usually worn out by that age, and it would have fouled the plugs along time ago. do the paper clip trick and check the engine codes

ok easiest way to solve this problem. O2 SIMULATORS! you can get them on ebay got like 80 bucks (for 2 if you have dual cats)

didnt i already say that?

ahh yes you did i didnt catch it

eh, i was just elbowin ya, still good advice, regardless of how many times we pound it into his head ;)

the way they were trying to explain it to me the sensor isnt sending the right information because of the loss of cats. thats why high flow cats were suggested, i dunno? oh i should mention he told me to take it to an exhaust shop for that and they dont get into that kind of work thats why i thought he was just tryin to help.

i really cant see how a cat would effect the O2 unless it create's a little backpressure so more exhaust stays in the pipes, and the O2 gets a little better reading, in which case it would seem kinda contradictory to put on high flow cats. i think the best bet is that the O2 is just plain junk. i would not recommend O2 simulators, ur giving the ecm one constant reading which isn't always going to be right, and on some days you'll see an improvement while other days it's gonna hurt gas milage and performance, and you'll wind up with fouled plugs..again

well you need to realize that the simulators are calibrated to make the engine run most efficent and get the most power. itis no more different thatn having the best high flow cats . it just affects the emissions mostely. it does not harm the computer. the one thing that does hower is the AIT simulator. this will be what will damage your engine

my heads starting to spin hehe. its been running better since having everything tuned but i still need some new plug wires which i should have soon. thanks for the help.

well you need to realize that the simulators are calibrated to make the engine run most efficent and get the most power. itis no more different thatn having the best high flow cats . it just affects the emissions mostely. it does not harm the computer. the one thing that does hower is the AIT simulator. this will be what will damage your engine

in a sense, yes they are calibrated to make the engine run most efficient, assuming that all running conditons are perfect. there telling the ecm that the mixture is right at 14.7:1 or what ever there programmed to tell and basing it's pulse width on that. but, while you can control what the ecm thinks the mixture is, you cannot control the numerous things that effect what the mixture should be: outside air temp, barometric pressure, air density, engine temp etc. your essentially running the ecm in open loop which is what it does for approximately 2 minutes of a cold start up. it bypasses the O2 and runs the engine off factory programmed settings, then it goes into closed loop once the engine is warmed up. i'll give an example, lets say you have O2 simulators and you start your car up on a 65 degree day and the sun is shining and your goin down the highway, the ecm goes into lean cruise mode wich is essentially open loop but it lean's out the mixture a little then bounces into closed loop every now and then to double check itself. the car is running good cause all conditions are near perfect, then it starts to rain and the outside temp drops 10 or 15 degrees, now the air is cold and dense. now the mixture doesn't like to attomise and runs like shit, but your O2 simulators is saying that everything is great. see what i'm gettin at? your paying for an O2 simulator, hurting performace and gas milage, and eventually damaging engine components cause you dont wanna buy a $20 O2 sensor. sorry to string this out but a little hard to explain

the o2 simulators are after the cats. this isnt changing what the air intake is. o2 simulators are safe. this thread was a popular one on my other fourm. the only one that matters to engine performance is the intake temp senser. the o2 simulators just read the gases after the cat. and if the cats are bad they read that the gases are too high. o2 simulators act like cats. they just let the exhaust gases be within standards. if the outside air changed the IAT senser would change the mixture and timing. and when it reads what the o2 senser (or o2 simulators) are readhing is reading that the cats are doing their job and keep the engine running efficient. i have never heard anywhere of o2 simulators harming an engine. the only reason their not street legal is for emission standards. and btw it goes into closed loop when the engine is on for more than 2 min, your crusing speed is about 70 mph, temp above 160 (i think thats the temp) i forget teh other variable. but the emission system is rarely used. alot of people think removing it will give more power but it dosent. when it goes into closed loop it recycles some of the exhaust gases. ive never heard of it "checking" itself. and the o2 sims dont hurt gas mileage they HELP it, it sode not dammage the engine and its just teling the comupter that the cats are running to their efficiency. i have has the simularots insalled for 4 months and my car idols a hella lot smoother, i got an extra mile to the gallon, and the performance is lot smoother and "thier"

well the way i see it, is you have O2 sensors upstream AND downstream of the cats. so for the sensors north of the cat, no problem, for the ones south of the cat, its a big deal, because the cat scrubs out excess HC that isnt burned in the engine, when the cat isnt there, that excess fuel coats and burns onto the O2 sensor, so its actually the sensor that fouls out, but this should also be making your engine run lean, not fat, so you could be burning your plugs with a too hot chamber, but then youd also be getting high NOx, so i dont know exactly what to tell ya. have you had the emissions ran sense this problem occured????? you can ask to have a tune up emissions test, and they cant fail you for that i think.

I would not simulate the 02 sensors on a TPI car. unless you want a constant set A/F raito that will kill your gas milage.( and with gas prices a 2.00 a gallon...) That sensor regulates fuel. The 02 simulators are to simulate the 02 sensors that controll the emmissions on the LS1 cars, which are the back two sensors. ( which as you all know has 4 o2 sensors) and to remove the cats and not trip the SES light on

You need to find out what the signal output of the o2 sensors, I think it should be between 760 and 800 milivolts at WOT. If they arenot within that spec, get an adjustible fuel pressure regulator and adjust the fuel pressure to conpensate.

sorry i thought you were talking about the upstream O2. and yes your right, the ecm does go into closed loop after 2min, which is what i said. i said it runs in open loop for the first 2 min

Just so im up to speed..? Sry guys.. im new, im learnin.. But i guess ya gotta start somewhere.

http://files.automotiveforums.com/gallery/watermark.php?file=/503/170598o2censor4.JPG

thats the pre cat O2 sensor, the other one should be in the exhaust pipe after the cat.

? well.. only other one i have seen is this one, on the other side. about a year ago i had the catalytic converter cut off, and had an exhaust put on..

http://files.automotiveforums.com/gallery/watermark.php?file=/503/170598o2censor1.JPG

and no engine codes?????? i mean the exhaust shop my have taken them off, but id think there would be a code. cuz im sure that you should have four O2 sensors.... pretty sure anyway. lol. they would be down under the car, bout where the front seats are. so you wouldnt see them from up top. but yeah, thats weird if those are the only two you have.

if i'm not mistaken the 93-95 have 3 sensers and the 96-97 have for (due to the intoduction of the dual cat's) the simulators that would replace the sensers are the down stream ones after teh cat

i went to a website to check prices/order new O2 censors, and under 93 camaro with the 3.4L engine, it only listed (2 required). others said 4 required.. so apparently there are only 2 on the 93.