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'86 coupe O2 test
This may be a stupid question, but......
I've got a Code 13 on my '86 coupe. Going through the trouble shooting chart and it says to get the engine up to normal operating temp. and ground the diagnostic terminal. Then look for a "Flashing Open loop or Flashing Closed loop" condition. When I ground the diagnostic terminal, my SES light starts flashing and continues to flash. What is this telling me? Is it indicating Open loop or Closed loop? TIA |
RE: '86 coupe O2 test
Just for more information, I've got Headman long tube headers on this car with a single-wire O2 sensor which is mounted near the collector.
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RE: '86 coupe O2 test
Generally speaking, an open loop would not send a signal, and a close loop would send the voltage signal. I would think there is a typo and you have a close loop flashing signal.
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RE: '86 coupe O2 test
So now I'm a bit confused. I'm relatively new at shooting these trouble codes, so bear with me.
I thought that, once the O2 sensor warmed up, it went into a "closed loop" condition and thats what I should be running with. Am I right or wrong in my thinking? Assuming my thinking is right, i.e., runs in "closed loop" what could be throwing this code? The O2 sensor is new. |
RE: '86 coupe O2 test
Do you have cats? Did your headers come with emission testing....hmm
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RE: '86 coupe O2 test
I only have the intermediate cat---got rid of the cats that were on the downpipes. Also have the EGR bunge in the passenger side header.
The reason I am going through all this is because the car has a hesitation when first starting out (not real bad once I going) and the engine seems to be holding back. This is my first Corvette and maybe I'm expecting more performance than I should. I've put new plugs, wires, rotor, cap, fuel line & fuel pump filters, checked the fuel pressure (39PSI), and adjusted the TPS to .54v. It was also dropping a 33 code. Went over the MAF sensor, checked for continuity & voltages and found nothing. Sprayed the contacts with some cleaner and haven't seen the code come back. |
RE: '86 coupe O2 test
MAF might just be wearing out....They do get old and die. Very exensive part which I hope it is not in your case. That 300 $$ can be put useful elsewhere.
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RE: '86 coupe O2 test
Could be timing/vaccum advance trouble?
I just bought my vette, so I don't know how everything works yet, but on earlier HEI iginitions, when you accelerate, 2 thing's advance the timing to help with the extra fuel burn. Vaccum pressure advances timing (higher RPM's create more vacuum), and the knock sensor advances the timing. Though I'd give you a few more thing's to add to you plate:D |
RE: '86 coupe O2 test
I've been playing with the timing. Started at 6*BTDC and now have it about 10*BTDC. Helps a little.
If I didn't know any better, this thing is acting just like the advance mechanism isn't working correctly. On older cars, you have the advance weights/springs. I really haven't looked into this one yet. Thats another possibility. The car sat for 3yrs. before I bought it so I'm wondering if something doesn't need "exercise" to get it working properly. |
RE: '86 coupe O2 test
Code 13 most likley means that your O2 has bitten the dust. Do you have a DMM(Digital Multimeter)? 86 has a 1 wire sensor and if it working properly on a warmed up engine, it should be cycling between .2 volts DC to .6 - .8 volts @ idle. You can unplug the sensor ( it may run a little sluggish) and test it with your voltmeter. If the voltage is staying sluggish and not actively switching, it is time to change the sensor. Also can test it by pulling vacuum hose loose from brake booster while idleing and watch the volt meter to see if it drop low quickly when you unplug the vacuum line. This tests the ability of the sensor to recognize low oxygen content in your exhaust. If it doesn't respond almost immediately, then time for a new one. Can likewise test the ability to go rich by spraying a touch of carb spray in a vacuum port to see if it will respond (voltage will go up to almost a volt), or by stabbing the throttle and it should do about the same thing. BTW, use a good quality O2, such as an A/C Delco, not an Autozone special, because good quality ones have quicker response times than the cheap ones. Good Luck. [8D]
Remember it's not leaking oil, it's leaking horsepower!! |
RE: '86 coupe O2 test
ORIGINAL: rwolak If I didn't know any better, this thing is acting just like the advance mechanism isn't working correctly. On older cars, you have the advance weights/springs. |
RE: '86 coupe O2 test
ORIGINAL: 86 Ironhead Could be timing/vaccum advance trouble? I just bought my vette, so I don't know how everything works yet, but on earlier HEI iginitions, when you accelerate, 2 thing's advance the timing to help with the extra fuel burn. Vaccum pressure advances timing (higher RPM's create more vacuum), and the knock sensor advances the timing. Though I'd give you a few more thing's to add to you plate:D Actually, when you open the throttle, engine vacuum drops until you reach a consistant rpm. And the knock sensor detects detonation via a quartz material inside it that vibrates and creates a miniscule voltage that the ESC module watches. If it generates the proper voltage, then the ESC retards the timing a couple of degrees to try and eliminate detonation. Sorry, just a little theory there. :D |
RE: '86 coupe O2 test
you might also look into getting a heated O2 sensor. some people have problems with the engine getting into closed loop with long tubes sense the sensor has trouble getting hot (needs to be something like 500F before the it can go into closed loop)
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RE: '86 coupe O2 test
Quick question----if it stays in open loop, what are the results? Running rich? Running lean? No power? etc?
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RE: '86 coupe O2 test
Open loop is in a richer mode because the computer is looking for certain criteria, coolant temp, O2 voltage, MAT sesnor temp, in other words it still thinks it is a cold engine because it has not seen all the criteria met for closed loop operation. [8D]
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RE: '86 coupe O2 test
Thanx to all for the input.
Has anyone converted to the 3-wire O2 sensor? If you have, what part # did you use? How did it work out for you?? I understand that all you need is a switched +12V source, ground, and the lead back to the computer. The more I read about O2 sensors, the more I think that mine isn't going into closed loop---so I'm looking to convert to a 3-wire unit. |
RE: '86 coupe O2 test
does your vette with long tube headers pass emmisions tests?
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RE: '86 coupe O2 test
3 wire sensors require a 12v source and ground for the heating element. The source has to be controlled on time in order not to burn up element, thus has to be controlled by ECM based on exhaust temp and coolant temp. Can't leave it on all the time or you are just wasting your money.
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RE: '86 coupe O2 test
MECH259??? Will you marry me???
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RE: '86 coupe O2 test
thespannerboys: Haven't attempted to take it thru emissions. Bought the car about a month ago as a project and just working on it to get it running right. The engine doesn't seem to have the punch I would expect out of this car. It bogs down when the gas is punched. Plus the fact that, once it warms up, the SES comes on and it kicks out a code 13. The O2 sensor is new and, from following the trouble shooting chart, it doesn't seem to be going into a closed loop condition. That's why I'm looking at the 3-wire option.
mech259: in everything I've found on 3-wire sensors, nothing has mentioned the 12v having to be controlled by time. Do you happen to know where I can pick up a "time controlled" 12v source? |
RE: '86 coupe O2 test
Well, really you shouldn't need it. 1st, you need to unplug your sensor, KOEO, check voltage on harness side of connector. GM sends a bias voltage to the O2 and measures reaction against it. Check for DC volts around .2v to .5v . If you are not getting bias voltage, then you have probably one of 2 things. Either there is an open to the ECM or the ECM is trash. Might need to pull the ECM out and do a circuit check from O2 to connector. Do you have a pin out of the ECM connectors? :)
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RE: '86 coupe O2 test
Ok, clue me in. KOEO????? I looked at the ECM yesterday and, as far as I can tell, I don't have a pin out of the ECM connectors.
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RE: '86 coupe O2 test
KOEO .... Key On Engine Off... If you have a fax number available, PM it to me and I will fax you diagrams and diagnostic procedure. [8D]
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RE: '86 coupe O2 test
Old post but relevant.I just did the warm up test..after a few minutes the voltage from the o2 sensor moved up to about .68 to .71 and just kind jumped a little up and down from time to time,+/- .03v .I doubt the vacuum test with the brake booster line would work on a non MAF car,but I tried anyway and the voltage didnt move much.I then blipped the throttle same thing..not any real noticeable voltage increase.I then gave a quick,small spray of starting fluid and the voltage jumped a little to like.79v.The reason I'm doing this is the car is running rich,does this sound like the O2 sensor needs replaced? It's a '90 with about 110,000 on it.The voltage from the ecm was steady at .4v also Thanx for any help |
RE: '86 coupe O2 test
ORIGINAL: BigRed90 Old post but relevant.I just did the warm up test..after a few minutes the voltage from the o2 sensor moved up to about .68 to .71 and just kind jumped a little up and down from time to time,+/- .03v .I doubt the vacuum test with the brake booster line would work on a non MAF car,but I tried anyway and the voltage didnt move much.I then blipped the throttle same thing..not any real noticeable voltage increase.I then gave a quick,small spray of starting fluid and the voltage jumped a little to like.79v.The reason I'm doing this is the car is running rich,does this sound like the O2 sensor needs replaced? It's a '90 with about 110,000 on it.The voltage from the ecm was steady at .4v also Thanx for any help Exactly what all is going on with the motor, besides the rich burn? And welcome into the forums there! |
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