Proving I need a heated O2...?
Thread Starter
Melting Slicks
Joined: Jan 2008
Posts: 2,065
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From: Jasper Texas
Proving I need a heated O2...?
Made another long trip Tuesday. Car ran great, got 25 mpg cruising 85mph.
One problem though, I could tell the car never, and I mean never, went into closed loop. The idle was always high after warm (1100 in drive, 1500 in park). When I let off the gas, the car didn't decelerate much at all like normal. I don't have to do any scanning to see open vs. closed loop when warm, the difference is obvious.
So, I guess I need a heated O2. Anybody have suggestions or personal advice they'd like to share?
One problem though, I could tell the car never, and I mean never, went into closed loop. The idle was always high after warm (1100 in drive, 1500 in park). When I let off the gas, the car didn't decelerate much at all like normal. I don't have to do any scanning to see open vs. closed loop when warm, the difference is obvious.
So, I guess I need a heated O2. Anybody have suggestions or personal advice they'd like to share?
Team Owner
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From: Athens AL
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If you were getting 25mpg at cruise, you were in closed loop. You might've dropped out, but you were getting to it.
Last edited by vader86; Sep 4, 2008 at 02:01 PM.
Melting Slicks
Joined: Aug 2003
Posts: 3,401
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From: Lakeville MI
An elevated idle speed has nothing to do with closed loop fuel control.
If your idle is that high you simply have too much air entering through the closed throttle blades, the IAC or through vacuum leaks that the IAC (if it is working as intended) cannot compensate for.
I would suspect that you have too much throttle opening and a high tps voltage.
I would suggest that you check the min air and tps voltage before considering a heated O2.
If your idle is that high you simply have too much air entering through the closed throttle blades, the IAC or through vacuum leaks that the IAC (if it is working as intended) cannot compensate for.
I would suspect that you have too much throttle opening and a high tps voltage.
I would suggest that you check the min air and tps voltage before considering a heated O2.
Thread Starter
Melting Slicks
Joined: Jan 2008
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From: Jasper Texas
well, ive let it idle for an extended period of time in diagnostic mode. I noticed when it goes from closed loop to open loop the idle picks up from 800 in park to 1500 in park. When it gets back to closed loop, it drops back down again.
Having said that....The car idled at 1500 rpms when cold today, instead of the normal stalling that happens. Whatever was causing the stalling/bucking when cold now seems to have swung the other way.
The IAC is a new ac delco unit, but I didn't install it. The tps checks out, and so does everything else that can be checked.
I'm going to pull the IAC and inspect it this weekend, I've got a funny feeling.
Having said that....The car idled at 1500 rpms when cold today, instead of the normal stalling that happens. Whatever was causing the stalling/bucking when cold now seems to have swung the other way.
The IAC is a new ac delco unit, but I didn't install it. The tps checks out, and so does everything else that can be checked.
I'm going to pull the IAC and inspect it this weekend, I've got a funny feeling.
Melting Slicks
Joined: Feb 2008
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From: Palm Beach
Let me see if I have this straight. Are you talking about idling with a jumper across AB on the ALDL? Is the car going in and out of closed loop at idle? If so, a heated O2 may be needed.
Regardless, you didn't get 25 MPG in open loop.
Do you have a laptop to datalog?
Le Mans Master
Joined: Feb 2000
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From: Kempner Texas
It's been my experience that a heated 02 is usually needed when (1) headers are installed and (2) the engine is at idle.
Under those two conditions, the stock UN-HEATED 02 sensor cools off causing the system to drop out of Closed Loop and return to Open Loop. As soon as the RPMs climb, the 02 sensor re-heats and the system returns to Closed Loop. Remember, the 02 needs to be at around 600F to be recognized by the ECM.
Because of the placement of the 02 in the header, the 02 cools down under idle conditions.
There may be other conditions that would call for installing a heated 02 sensor, but I've never come across them. I have to agree that if you were getting 25 MPG, the system had to have been in Closed Loop.
Jake
Under those two conditions, the stock UN-HEATED 02 sensor cools off causing the system to drop out of Closed Loop and return to Open Loop. As soon as the RPMs climb, the 02 sensor re-heats and the system returns to Closed Loop. Remember, the 02 needs to be at around 600F to be recognized by the ECM.
Because of the placement of the 02 in the header, the 02 cools down under idle conditions.
There may be other conditions that would call for installing a heated 02 sensor, but I've never come across them. I have to agree that if you were getting 25 MPG, the system had to have been in Closed Loop.
Jake
Thread Starter
Melting Slicks
Joined: Jan 2008
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From: Jasper Texas
Yes, I was running the car with the ab jumped, noticed it wouldn't go into closed idle progressivly rose, then finally went in...about a minute later it kicked out and idle picked up again. I've also felt this sensation when cruising slow speeds before.
I need a heated O2, no doubt. But that is not causing the high idle problem, the O2 does nothing cold. So I'm looking at that IAC.
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Thread Starter
Melting Slicks
Joined: Jan 2008
Posts: 2,065
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From: Jasper Texas
I'm making a new thread later for the idle condition. Overnight, it went from bucking/stalling/hunting when cold and good and smooth when warm to good and smooth all the time, just at 1500 rpms! I backed out and chirped my ET streets shifting to drive right infront of a cop today! 
Out of curiosity, the next time I drive, I will leave the ab jumped for a while and see what exactly is going on.
Out of curiosity, the next time I drive, I will leave the ab jumped for a while and see what exactly is going on.
Melting Slicks
Joined: Apr 2004
Posts: 2,775
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From: cyberspace NY
I havn't done it in a long time, but depending on how fast it blinks, is how much fuel it is adding, or subtracting. something like that.
I drove around like that for a day to learn about it.
I drove around like that for a day to learn about it.
Drifting
Joined: May 2008
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From: Denver, NC
For what it's worth - I do a lot of O2 and fuel injection work on cars and motorcycles. Many times when people install free flowing exhaust (more so on certain motorcycle configurations than cars) or systems that re-locate the O2 (both cars and bikes), the unheated ones will cool off intermittantly - especially at idle. They then toggle in and out of closed loop. I have even seen them go into open loop going down the road on some motorcycles because of the combination.
Thread Starter
Melting Slicks
Joined: Jan 2008
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From: Jasper Texas
With a and b jumped In closed loop only = if the cel lights up for about 2 seconds and goes off for .5 seconds...the O2 is seeing a rich condition. If the cel lights up for .5 seconds and goes off for 2 seconds, the O2 is seeing a lean condition. If it is on and off for equal amounts of time, the O2 is seeing normal burn.
Mine has always shown as normal burn, though obvious that I'm running rich, smells like a gas station back there.
Mine has always shown as normal burn, though obvious that I'm running rich, smells like a gas station back there.
Melting Slicks
Joined: Apr 2004
Posts: 2,775
Likes: 138
From: cyberspace NY
For what it's worth - I do a lot of O2 and fuel injection work on cars and motorcycles. Many times when people install free flowing exhaust (more so on certain motorcycle configurations than cars) or systems that re-locate the O2 (both cars and bikes), the unheated ones will cool off intermittantly - especially at idle. They then toggle in and out of closed loop. I have even seen them go into open loop going down the road on some motorcycles because of the combination.
Drifting
Joined: May 2008
Posts: 1,695
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From: Denver, NC
I would doubt it should toggle into open loop with a stock manifold after it's warmed up but I'm not proclaiming to be an expert on the strategies in these cars. However, I have seen the reversion effects of open exhaust affect sensors with stock head pipes and very free flowing mufflers on many motorcycles.
The condition you're describing can be a result of ECM/PCM strategies, rich conditions, idle speed etc. It could even be normal - I'm not intimate with the strategies of these cars yet. I just wanted to share a little knowledge gained over the years.
Last edited by Ed Ramberger; Sep 4, 2008 at 10:30 PM.
Instructor
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From: Tampa Florida
check this
check black ground wire from spark control box on firewall near pass. side door hinge . trace it to back of block ground... 3x3 inch flat box probaly 6 wires or so out of it one is to block.. If motor was out may not got put on . Craig C.
Team Owner
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From: SE NY
Cruise-In II Veteran
Are you talking about idling with a jumper across AB on the ALDL? Is the car going in and out of closed loop at idle? If so, a heated O2 may be needed.
If the SES flash rate stays at 2Hz or increases to 2Hz after idling a while then a heated sensor is needed, else no.
Thread Starter
Melting Slicks
Joined: Jan 2008
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From: Jasper Texas
Craig, thanks for that little piece of advice. the esc circuit was giving me fits for a long time (or so I thought). I've never fixed the problem, just thought I ruled it out...maybe not. I'll check it this weekend.