Ok so I changed my exhaust this winter by removing my resonator and added X-pipe. The exhaust flows much better and felt a set of pants power gain. I think my 383 was choked up on the exhaust some. The car runs awesome but really stinks at idle and is blowing some light smoke when getting on the throttle wide open. I thought she was running a little rich and a couple of spark plugs showed the same. So I hooked up my Data Master data-logger and it shows the motor never comes out of OPEN LOOP and injectors/fuel trim are showing out of range. I am also getting a data log code for charcoal purge canister? (not sure what this does) I did remove all emissions stuff after my engine build.

Brief engine history: 383 rebuild with lumpy, cam 58mm TB, long tube headers and worked over heads. Basic 450hp 383ci build. I had PCMforless do the first tune and a retune after break-in from same data-logging program used this time i.e. (free internet download).

Questions: Could the rich condition be from the OPEN LOOP? Can someone with experience reading data be willing to look at my info if emailed? I have read post in the past about changing the O2's to a heated sensor with two or three wires instead of the stock setup. Last, does anyone know what this charcoal purge canister code is from?

I would love any help from people knowledge on these issue etc. Thanks! Randy

 

I'm in SE Iowa and had to go to a heated O2 sensor to get my car to stay in closed loop when I put my longtubes on. I imagine it's pretty rich if you're running in open loop all the time.

 

What year?
Was the canister purge activation removed in the tune?

How LUMPY? Specs?

What are the O2 readings from your datalog?
Are they varying as they should or are they one fixed MV figure

Before I went to a heated 02 ,I only had the stock O2 fitted in the collector of my LT's drop out at idle.
As soon as I drove off , the O2 came back online and engine went closed loop

 

So your charcoal canister is gone? The ECM checks for the purge solenoid and apparently is setting an error code because it's not connected. You can get the check for this removed in the tune.

 

Which is why I asked for the model year since the purge diagnostics feature is only found on late OBD1 cars.
Early ECM's turned the CCP on and adjusted the fueling ,assuming the canister was fitted and working; there was nothing to say CCP was even in the car

 

My vette is a 92. I can't remember what the canister looked like or if I removed it, 3yrs ago. It isn't throwing an engine light code, it just shows up in red on my datalogging program codes.

I will have to get my cam card but I think it was like 230 duration and 540 lift at 112 LSA.

I am at work and don't know remember the O2 reedings but I think they varied. I did drive the car about 3-4 miles at verying speeds and throttle but she never came out of closed loop.

Are the heated O2's considered wide band?

Would love someone to chime in who knows and willing to reed data.

 

That wasn't clear to me. I thought you were getting an error code. According to the "official" list, the canister error code is only available on '94 and newer cars.

On early cars the canister is under the driver's side headlight. It was moved to the rear some time in the '90s -- I don't know what year. I believe it's on the passenger side next to the gas tank.

 

No
Just a narrow band with a heater element to ensure the sensor reaches ( faster ) and maintains it's correct operating temp under all conditions

 

OK I do remember removing a black canister of some sort with a small electric fan on it that was up in front of the drivers side wheel well. That may be what it was. Will this effect the fuel mixture conditions or have anything to do with the 02 readings?
Will going to heated 02's get me out of closed loop?

 

Sounds like the A.I.R pump.

 

Can someone tell me what the charcoal purge canister does? I only have service manual #1 and it said to see manual #2 under emissions. Thanks!

 

http://www.autoshop101.com/forms/h62.pdf

Some interesting read regarding disabling CCP in the tune

http://www.thirdgen.org/techboard/di...-cell-blk.html
http://www.thirdgen.org/techboard/di...-cell-4-a.html

 

Thanks for all your help guys. I sent my info back to PCMforless to see what they think. I did go through my charcoal canister lines last night and cleaned them. If that doesn't help I may pull the canister and do the test Vetteoz sent. Not sure if this is what's causing my rich mixture. I may have to look into getting a dyno tune and installing an adjustable fuel pressure regulator so I can drop my pressure a little. I am only running 42psi now with stock fuel system and 30lb inj. Got to go Mothers day and all. Thanks!

 

When you're running in open loop mode the ECM is calculating the injector pulse width based on coolant temperature tables. It's just guessing because it has only a vague idea of what's really happening with your engine.

The ECM richens the mixture at low coolant temperatures. If the CTS (Coolant Temperature Sensor) is bad or has a bad connection it can fool the ECM into thinking the coolant is cold and the car will run rich.

If you're running long tube headers then you definitely need heated O2 sensors. If the O2 sensors don't get hot enough the ECM will never go into closed loop mode. The ECM decides to go to closed loop mode when the coolant temperature is high enough and the O2 sensors put out over about 0.5 volts.

Check your coolant temperature, injector pulse width and the O2 sensor voltages. Sometimes putting in large injectors will cause an idle problem because the ECM has a minimum pulse width limit. If it hits the limit you will run rich. That shouldn't be a problem with the 383, as 30 lb. injectors are about the right size for that engine.

 

Thanks! Cliff,
I just got an email from PCMforless and they said the left bank is really rich. Possible causes maybe exhaust leak (no leak) bad O2 sensor or sensor wire (not showing a code?). Could the O2 be bad and not throw a code? I don't have heated O2's but my data shows it going into closed loop fairly soon?
Does anyone have the part number for the heated O2 sensor and the do I need a $90 connector kit or can this be wired up fairly easy without? I think I will start here and see what happens.

 

You don't need the $90 connector kit, it is pretty easy to wire yourself. A three wire connector from any parts store is nice if you ever want to remove the 02's. I found a keyed on hot connection where my AIR pump was, I think you said you removed yours, so did I so I just went to that connector for the wire to the heater. The other 2 wires are ground and the wire to the computer. I can't remember how I found the part number for the heated 02's hopefully I'll remember or someone else will know.