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Car running rich

supernatural400

Well-known member
Joined
Feb 25, 2001
Messages
410
Location
massachusetts
Corvette
1993 SuperNatural 400 #5 /99 LS1 Z28 N2O equipped
Will a bad O2 sensor always throw a code, or can it be bad and not set it off. I'm trying to narrow down and exhaust smell at high throttle. My son was following me one day doing about 75-80 and he tells me he can really smell the exhaust so I'm searching for the reason. I have diacom software so I guess I'll have to find the voltage to see if thats the problem. I also noticed I'm getting some injector sounds that seem kinds loud. any suggestions ?
 
D

dgoodhue

Guest
A bad O2 can cause the car to run rich. Looking at the O2 sensor voltage is going to be useless in closed loop. A properly working O2 will cycle back and forth from ~100mv to 900mv. I make sure the )2 are moving back and forth and I would look at you BLM to see if there around 128 instead.
 

-=Jeff=-

Well-known member
Joined
Feb 2, 2001
Messages
909
Location
Bartlett, IL. (Chicago Suburb)
Corvette
1990 ZR-1
Also unplug eachinjector and use an Ohmmeter and check the impedance on each one..

That could also cause the rich condition if one is going bad and leaking
 

supernatural400

Well-known member
Joined
Feb 25, 2001
Messages
410
Location
massachusetts
Corvette
1993 SuperNatural 400 #5 /99 LS1 Z28 N2O equipped
Checked out the O2 sensors with diacom tonight and they seem right on the money. running between 100 and 900mv like they should. although at 4000 RPM's they did seem to be running around 500mv which is a little rich. didn't really get any funny smells this time out of the exhaust, could have been on the day that I though it was running rich, was because the car sat for 2 weeks without driving it. still on the hunt:t
 
D

drcorvette

Guest
Hey Jeff ... can you explain to me how to check the impedance???
And what should it be????

Thanks
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
O2 sensor

My milage went in the toilet a while back in my L98 12.9 MPG avg.. No codes but STINKY RICH all the time. Then a week later I got the O2 code. I replaced the sensor ( 45.00 ) the old one was sooty. Now were back to normal 17.9 city 22 Hwy and no stinky... but a slight ping off idle when I accelerate normally, AC on, Middle of the day Water temp 205 ish...

My .02

Vig!
 

WhalePirot

Well-known member
Joined
May 9, 2002
Messages
2,942
Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
The O2 sensor is good for up to 50Kmiles, or so. Poor ignition, due to bad plugs/wires can soot it up, and clog the cat. I fixed the overdrive on my 4+3 by changing plug wires. That's all I did and it stopped shifting on and off. I figured it was an incomplete burn, in one or more cylinders, fooling the ECM, through the O2, into an open loop condition.

Low vacuum, at the manifold pressure sensor, can fool the ECM into thinking that a full-throttle condition exists, so it pumps more fuel to adjust. When I changed to a more aggressive camshaft, I had low vacuum and a very rich running car.

Check the electrical side and the vacuum, too.
 

-=Jeff=-

Well-known member
Joined
Feb 2, 2001
Messages
909
Location
Bartlett, IL. (Chicago Suburb)
Corvette
1990 ZR-1
drcorvette said:
Hey Jeff ... can you explain to me how to check the impedance???
And what should it be????

Thanks

Sure.. Make sure you have a DMM (Digital Multi- Meter) to check the Ohm's on the injectors.

Unplug each injector and put the leads from the DMM across the to connector pins on the injector. Each one should be above 12ohms.
 
B

boblx2a

Guest
A good use for the Diacom software I have found is to run a trace at least once a month and print the traces. Then each month as you print a new trace compare it to the previous printouts to see if anything is changing. This of course assumes that the Vette was in good shape to begin with.
The other thing is there are about 32 variables on a Diacom's Vette printout. You have to choose which variables are the most important for you to print.
This way you are comparing apples to apples instead of guessing what it should look like. Diacom explains the parameters okay but it is good to see what it actually looked like when it was running well.

Good luck with it.........
 

supernatural400

Well-known member
Joined
Feb 25, 2001
Messages
410
Location
massachusetts
Corvette
1993 SuperNatural 400 #5 /99 LS1 Z28 N2O equipped
I 'm leaning towards new plugs, I've noticed lately a little hesitation not always but somtimes. the wires were replaced last year with MSD 8.5 as was added the MSD 6AL box .should have done the plugs at the same time, because their a ***** to do
 

-=Jeff=-

Well-known member
Joined
Feb 2, 2001
Messages
909
Location
Bartlett, IL. (Chicago Suburb)
Corvette
1990 ZR-1
supernatural400 said:
I 'm leaning towards new plugs, I've noticed lately a little hesitation not always but somtimes. the wires were replaced last year with MSD 8.5 as was added the MSD 6AL box .should have done the plugs at the same time, because their a ***** to do

Can you disconnect the 6AL and run stock without too much trouble?

if so try that first, unless you already have. I have heard of too many people have trouble with the 6AL boxes
 

supernatural400

Well-known member
Joined
Feb 25, 2001
Messages
410
Location
massachusetts
Corvette
1993 SuperNatural 400 #5 /99 LS1 Z28 N2O equipped
it unhookd fairly simple, have ad the box in for over a year now with now problem.
I noticed that it does not seem to be running rich just on normal driving, a friend the other day was following me and when I got on it , he said there was a small puff of dark smoke and he could smell fuel for a little bit. callaway tells me these cars a set to run rich at WOT, so maybe thats the answer. I'll try the plugs anyway just to see if it makes a difference
 
B

Black Ice

Guest
My guess is the Mass Airflow sensor. This unit controls Air/Fuel mixture. I had that "rich" fume smell also as soon as the MAF was replaced the smell was gone. The car goes into a "rich" default mode when the MAF fails.
 

-=Jeff=-

Well-known member
Joined
Feb 2, 2001
Messages
909
Location
Bartlett, IL. (Chicago Suburb)
Corvette
1990 ZR-1
Black Ice said:
My guess is the Mass Airflow sensor. This unit controls Air/Fuel mixture. I had that "rich" fume smell also as soon as the MAF was replaced the smell was gone. The car goes into a "rich" default mode when the MAF fails.

Can't be.. no MAF on a 93
 

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