88, code 44
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From: Warner Robins GA
88, code 44
I'm getting a very strange problem every now and then. I'll be driving along like normal and my Check Engine light will come on. The code says 44, Oxygen Sensor (lean). Nothing at all seems to change and the car doesn't hiccup when this occurs.
The oxygen sensor is about a year old so I'm hesitant to replace it again unless I'm pretty sure it's the problem.
About the same time this problem started popping up, another problem started as well so they're probably related. I'll be driving along and everything is fine. I'll come to a stop and my idle is higher than normal, around 900 rpm while it's warm. It's an automatic, so I've tried putting it in park. This just makes the idle go up to about 1100. If I turn off the car and immediately turn it back on, everything is back to normal. The code 44 typically shows up sometime during the drive after the idle problem occurs.
The IAC and TPS are also relatively new, and TPS voltage looks good at both idle and WOT. I know the IAC is set correctly as well. They worked well for about a year before this started happening. I've already checked for vacuum leaks to the best of my ability, and gave my throttle body a good cleaning. EGR is new so I doubt it's sticking.
If the screwy idle and the code44 are indeed related, I don't think it'd be something as trivial as the throttle sticking. The ECM (also new) is probably seeing a bad sensor that's throwing other settings off.
To make it even worse, my autoxray that works on every other Chevy I've tried it on doesn't work on my Corvette. I have to take it to my friend's shop to pull data.
Any clues where to start? I've thrown more parts at this car than I'd care to admit, and throwing parts in it that I've already replaced doesn't sound appealing. Maybe if I can hear from some other people that have had similar idle issues I could go from there.
The oxygen sensor is about a year old so I'm hesitant to replace it again unless I'm pretty sure it's the problem.
About the same time this problem started popping up, another problem started as well so they're probably related. I'll be driving along and everything is fine. I'll come to a stop and my idle is higher than normal, around 900 rpm while it's warm. It's an automatic, so I've tried putting it in park. This just makes the idle go up to about 1100. If I turn off the car and immediately turn it back on, everything is back to normal. The code 44 typically shows up sometime during the drive after the idle problem occurs.
The IAC and TPS are also relatively new, and TPS voltage looks good at both idle and WOT. I know the IAC is set correctly as well. They worked well for about a year before this started happening. I've already checked for vacuum leaks to the best of my ability, and gave my throttle body a good cleaning. EGR is new so I doubt it's sticking.
If the screwy idle and the code44 are indeed related, I don't think it'd be something as trivial as the throttle sticking. The ECM (also new) is probably seeing a bad sensor that's throwing other settings off.
To make it even worse, my autoxray that works on every other Chevy I've tried it on doesn't work on my Corvette. I have to take it to my friend's shop to pull data.
Any clues where to start? I've thrown more parts at this car than I'd care to admit, and throwing parts in it that I've already replaced doesn't sound appealing. Maybe if I can hear from some other people that have had similar idle issues I could go from there.
Drifting
Joined: May 1999
Posts: 1,478
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From: Sacramento, CA Money can't buy happiness - but it's more comfortable to cry in a Corvette than a Yugo.
Code 44 is a low voltage in the O2 sensor circuit. The 88 Factory Shop Manual has a troubleshooting chart specifically for diagnosing a code 44. See page 6E3-A-54 and -55.
From the FSM, some possible causes of the code 44 are:
1) O2 sensor wire mispositioned and touching the exhaust manifold.
2) Intermittent ground in wire from the O2 sensor to connnector.
3) MAF Sensor: MAF output that causes the ECM to sense a lower than normal air flow will cause the system to go lean. Disconnect the MAF and if the problem stops, replace the MAF.
4) Fuel pressure: monitor while driving the car. If too low under load it will cause a lean condition.
5) Fuel contamination: Water, even in small amounts, cna be delivered to the injectors and can cause a code 44 condition.
6) Lean Injectors: perform an injector balance test.
7) Exhaust or vacuum leak
8) AIR System: In "closed loop", if the block learn value goes down, while squeezing the air hose to the left side exhaust ports refer to chart C-6 for AIR System diagnosis.
9) If all of the above passes, suspect a faulty O2 sensor.
From the FSM, some possible causes of the code 44 are:
1) O2 sensor wire mispositioned and touching the exhaust manifold.
2) Intermittent ground in wire from the O2 sensor to connnector.
3) MAF Sensor: MAF output that causes the ECM to sense a lower than normal air flow will cause the system to go lean. Disconnect the MAF and if the problem stops, replace the MAF.
4) Fuel pressure: monitor while driving the car. If too low under load it will cause a lean condition.
5) Fuel contamination: Water, even in small amounts, cna be delivered to the injectors and can cause a code 44 condition.
6) Lean Injectors: perform an injector balance test.
7) Exhaust or vacuum leak
8) AIR System: In "closed loop", if the block learn value goes down, while squeezing the air hose to the left side exhaust ports refer to chart C-6 for AIR System diagnosis.
9) If all of the above passes, suspect a faulty O2 sensor.
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Joined: Aug 2002
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From: Warner Robins GA
Originally Posted by Mike_88Z51
Code 44 is a low voltage in the O2 sensor circuit. The 88 Factory Shop Manual has a troubleshooting chart specifically for diagnosing a code 44. See page 6E3-A-54 and -55.
From the FSM, some possible causes of the code 44 are:
1) O2 sensor wire mispositioned and touching the exhaust manifold.
2) Intermittent ground in wire from the O2 sensor to connnector.
3) MAF Sensor: MAF output that causes the ECM to sense a lower than normal air flow will cause the system to go lean. Disconnect the MAF and if the problem stops, replace the MAF.
4) Fuel pressure: monitor while driving the car. If too low under load it will cause a lean condition.
5) Fuel contamination: Water, even in small amounts, cna be delivered to the injectors and can cause a code 44 condition.
6) Lean Injectors: perform an injector balance test.
7) Exhaust or vacuum leak
8) AIR System: In "closed loop", if the block learn value goes down, while squeezing the air hose to the left side exhaust ports refer to chart C-6 for AIR System diagnosis.
9) If all of the above passes, suspect a faulty O2 sensor.
From the FSM, some possible causes of the code 44 are:
1) O2 sensor wire mispositioned and touching the exhaust manifold.
2) Intermittent ground in wire from the O2 sensor to connnector.
3) MAF Sensor: MAF output that causes the ECM to sense a lower than normal air flow will cause the system to go lean. Disconnect the MAF and if the problem stops, replace the MAF.
4) Fuel pressure: monitor while driving the car. If too low under load it will cause a lean condition.
5) Fuel contamination: Water, even in small amounts, cna be delivered to the injectors and can cause a code 44 condition.
6) Lean Injectors: perform an injector balance test.
7) Exhaust or vacuum leak
8) AIR System: In "closed loop", if the block learn value goes down, while squeezing the air hose to the left side exhaust ports refer to chart C-6 for AIR System diagnosis.
9) If all of the above passes, suspect a faulty O2 sensor.
O2 sensor itself is new. I've checked to make sure it hasn't grounded against the exhaust.
MAF is new.
Checked fuel pressure and make sure it was set correctly (adjustable regulator).
New injectors.
Checked for vacuum leaks.
AIR system has been gone for quite some time.
I'll check for exhaust leaks, but I thought I might be able to hear one if it was there.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
What year AutoXray do you have? My XP240 works fine on my '88 though I've had problems with '85s.
It really would be helpful if you could just switch on your scanner when the problem surfaces. If we were close I could bring over my scanner to see if it works on your '88.
Since it can be scanned at the shop the problem must be with your scanner or it's cable. Verify that you have the proper config set up for a '88 Vette, i.e.:
-88 = Year code
-8 = 8th VIN digit
Since it happens after cruzin for a while I'm suspecting it's EGR related, that is, a vacuum leak caused by the ECM opening up EGR flow.
It really would be helpful if you could just switch on your scanner when the problem surfaces. If we were close I could bring over my scanner to see if it works on your '88.
Since it can be scanned at the shop the problem must be with your scanner or it's cable. Verify that you have the proper config set up for a '88 Vette, i.e.:
-88 = Year code
-8 = 8th VIN digit
Since it happens after cruzin for a while I'm suspecting it's EGR related, that is, a vacuum leak caused by the ECM opening up EGR flow.
Last edited by 65Z01; Oct 11, 2005 at 06:46 PM.
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Joined: Aug 2002
Posts: 715
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From: Warner Robins GA
Originally Posted by 65Z01
What year AutoXray do you have? My XP240 works fine on my '88 though I've had problems with '85s.
It really would be helpful if you could just switch on your scanner when the problem surfaces. If we were close I could bring over my scanner to see if it works on your '88.
Since it happens after cruzin for a while I'm suspecting it's EGR related, that is, a vacuum leak caused by the ECM opening up EGR flow.
