I've just installed a 355 w/ vortec heads, rv grind cam, using a 2" tbi. 747 ecm. I'm using Edelbrock TES headers, with the bung for the O2 already on them at the collector. Using AutoXray, I can see that the engine is staying in closed loop. BLM and integrator stay locked at 128, O2 voltage is pretty much constant at about .447. I have not yet disabled EGR, even though I don't have it. How do you do that on this ECM? I just plugged the line. What can be preventing closed loop operation? The coolant temperature evens out at 180. Is the 02 not getting hot enough? Also I have tapped into the 02 lead for a LED rich/lean display. The exhaust smells rich. Thanks.

 

I'm a little confused; (which ain't the first time.)

First you said it stays in closed loop and then later you ask what could preventing the system from going into closed loop.

I'll assume you meant the engine stays in open loop with BLMs and Int locked at 128 and 02 voltage at 447.

There are several parameters that must be met for an ECM to go into closed loop. One of them is that the 02 sensor has to reach a temperature of 600 degrees F.

That could be your problem, assuming you aren't getting any codes.

A lot of times, guys with aftermarket headers have to swap to a heated 02 sensor in order for their systems to go closed loop.

I'm betting that's what's happening to you.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

 

Yes, I'm sorry, the motor stays in open loop. I'm getting a good number of cross counts and the rich/lean flag flip flops every couple of seconds. Is this just artificial becuase of the BLM being locked at 128? Also, how do I disable the EGR in this chip? I'm using ANLW5469 .bin. I've heard of setting the temp for the egr to come on at 255 or whatever, but this bin doesn't have an EGR enable temp, it appears to be relative to % TPS. Could I set it to come on at 100% TPS or something? Thanks again. Oh yeah, and no codes, not even EGR (and I don't have the code 32 disabled)

[This message has been edited by jobrya (edited February 24, 2001).]

 

Well, I just took it out for a little while, and sure enough got code 13 02 sensor failure. Cleared it, and got it again, so I guess that is the problem. Can anyone suggest a heated sensor, and a method of wiring it?

 

I already bought the Bosch 13077 3-wire heated sensor. Its for a '92 ZR1 vette. However, GMECM recommends the AC Delco 4 wire heated O2 sensors. These have an extra wire for a redundant ground. Very good idea. I will be wiring mine using the 12V switched power at the Fuel Pump Relay (driver's side rear against firewall). Make sure to mount a fuse in-line for that 'just in case' scenario. I'll be using a 3A fuse based on Mike Davis' recommendation.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
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