:crazy:

While I'm trying to diagnose a slight perfomance problem, I'm starting to wonder if the heated O2 sensors are worth changing since they seem to be critical in providing feedback info to the computer.

Plugs (NGK TR55's), Wires (Magnecor 8.5mm) and a TPIS AFPR were recently installed. When I "goose" the throttle (in neutral), I'm seeing a puff of what appears to be black smoke from the exhaust. At idle, there is no smoke visible, but when I give it a good rev, it 's quite noticeable. I"ve also noticed a slight build-up of black soot in the tail pipe, but don't know whether it's normal or not (probably just regular 'ol exhaust emissions....)

Also, when I ran at Island Dragway back in July, one guy I know mentioned to me that he saw black smoke exiting the exhaust after I took off from the line.

Could I possibly have bad O2 sensors., or any other ideas.....

what is the p/n for the O2 sensors (or a good aftermarked piece), and expected cost??

Any ideas?

Thanks,
Dave

 

i replaced mine with the bosch sensors. $18 a piece from autozone.
they work fine.
regards
ds :jester

 

dsky, you guys are lucky on the east coast. Replaced all 3 of mine this weekened, and boy about 4 mpg difference. But for me at Autozone it was $49.99 and Pep-Boys $59.99 a piece. This is for Bosch 15703's. Is this what you got?, and if so what east coast needs O2 sensors less than west coast. Besides that I had to go to 2 different stores to get the whole set, and replacing them was a b@#%&! But like everything once you do it once it will be much simpler the next time. :cheers:

 

Is that p/n correct for the O2 sensors ???

TIA,
DAve

 

Yep, 15703 from Bosch is the replacement. Again for me $49.99 and $59.99. :smash:

 

You've got a rich condition if it's emitting black smoke. Aren't these Cars FUN? :rolleyes: Try a new 02..it can't hurt. LUCKILY, you're within two hours of Callaway. I'm sure they'll lend you a hand. I am less fortunate as LPE is 10 Hours away. If all else fails, bring it to CT.

JD

 

Black smoke is unburned fuel. i.e. You have too much fuel pressure. Back off the AFPR. (Not too far, too little fuel, and you will burn engine parts.)
throttle movements puts the ECM into Open Loop mode. Open loop mode uses preset numbers for fuel and spark. i.e. The O2 sensor signal is ignored during Open Loop mode.

AFPR is a tuning tool. If you don't know how to tune,..., learn how to, or don't bother putting one in. (No slam)

 

how about starting with the other options, you said you just added a fuel pressure regulator? what is the psi setting. by raising your pressure you are also richening your mixture, i imagine that your O2's are getting there fair share of carbon build up from it, but i would hate to see you replace O2 sensors at that price only to carbon and gum them up again from a rich condition. remember when fuelk pressure is raised, it richen the mixture up throughout the driving range. so when tuning the regulator there can be an overkill point where you will actually see a performance decrease. i know on our LT4, we tried settings from 38psi up to 57 psi, we opted for the richer condition because the car isn't a daily driver and we would rather run a little on the rich side to save expensive parts ie... pistons, block etc.. i bet if your pipes are black, your exhaust ports on your heads probably look like a new darker shade of coal! if remnoving your headers is an option, not to hard if they are aftermarkets, i think after you get everything tuned in right you could swivel the headers back a little while still bolted to the exhaust system and remove the valve cover loosen the exhaust rockers to close the exhaust valves and decarbon the ports (i use carbon guard, let it soak for a bit then use a scotchbright scrubby to help speed things along) finally once you feel you have removed most of the carbon and your satisfied with your job replace the exhaust rockers and valve covers and rebolt the manifolds to the head. also a good time to get to your plugs if their in need. a carboned up port flows much less then a cleaned port and also has higher temps in the head, nice little tip for tuning. thats why head porters usually mirror finish the exhaust ports, to do two things, reduce any frictional surfaces that may acts as a heat transfer point or that may be prone to start building up carbon deposits and in turn this also raises the flow characteristics of the port for more efficient exhaust gas scavenging. might pick up a few extra ponies, im not claiming a big gain but the car will love you for it! and remember i recommend this after you straighten the tuning out!

added note*
-when i pulled the heads of to be ported, the exhaust ports had close to 1/32" of carbon built up completely and uniformely on the exhaust ports. now everyone is always screaming about getting better flowing heads, if for a days work you can improve your current head flow for the cost of a scrubby pad and a can of carbon guard, doesn't it make sense? i thought so!


just a thought,
chris :cheers:


[Modified by lcvette, 12:43 PM 9/5/2001]