My '91 TBI has been thowing a Code 13 for a couple months now, and I've been meaning to get to the bottom of it. It generally only happens when I'm cruising at a constant RPM for awhile. Starting the other day, however, my car began stumbling. It's pretty reproducible, and the severity increases with RPM. It's only really noticeable at 2.5k and above, and happens when I let off the gas, or when I'm just giving it enough to maintain speed. At 2.5k it's a light shake... at 3k the whole car bucks Acceleration, however, is perfect.
Browsing through other posts, I found a reasonable amount of information about other people's issues with code 13. My O2 sensor only has about 1k on it, I replaced it when the otherone hit the manifold and melted. Today I moved the wire away from the spark plug wires, and anything else that moves electricity, but it did not help. Some posts refered to bad ground being a possibility, but I don't know where to check for that. I saw something about an engine ground strap that runs from the pass head to the firewall, but that area is so littered with hoses and cables it's hard to tell. Can anyone confirm the location ? I may end up going back to autozone and grabbing another O2 sensor just to make sure, and clean out the flange at the same time for good contact. Any other ideas ?


Kyle

 

Ok, I broke out the DVM and did some monitoring of my O2 sensor while driving around. As I understand it, the readout from the sensor is supposed to change quote often. I was using a $70 craftsman DMM, and as I was cruising the voltage readings only changed my .03v either direction. I'd have to say the average at cruise (~2000 rpm) was about .54v, and it went up or down a few mV evey second or two. Only rarely did the readings change rapidly, and at one point they even hit 1.2v. This happened immediately after the ECM tripped a code 13 (after the light went off exactly, the whole time it was on it was close to constant). From what I've read, if the ECM doesn't see constant switching from the O2 it can set off this code. Based on the info I gave, does this sound like it could be the cause of the code ? If so, I'll look into possibly a) a new sensor, or b) tracing the wiring even further and checking for any damage.



Kyle

 

In case anyone is following this Today I yanked a few of my degraded vacuum lines, and replaced them with brand spankin new ones. It helped tremendously, but didn't exactly fix the problem. I now have good brake pressure, and the ECM codes aren't coming quite as often (but I'm still getting a code 13 every 10 miles or so), but the stumbling still happens at light throttle. I'm going to finish replacing the lines this weekend and check around for any vacuum leaks, but I think I pretty much have that nailed now. I'm not getting any other codes besides 13, so aside from the possibility of still having a vacuum leak, does anyone have any ideas on what else it could be ? I hope to have an ALDL interface built by this weekend, so I can post some data from WinALDL.


Kyle

 

Well you've figured out a lot, so I'll toss in a bit of info, you know full well a code 13 is the general O2 sensor trouble. This happens if there is an open circuit ie disconnected o2 sensor, broken wire etc OR if the mixture is just rich. O2 sensors will screw up, a code 13 flag is raised when the o2 sensor gets covered by carbon. Hope you figure it out.

 

Ok, I got some data out of WinALDL. Overall the car was acting better than usual, but near the end of the datalog (about 10 entries back) I got it to start stumbling real bad, but no code 13. The funny thing is the ecm never seemed to register closed loop operation, most likely because of the funky O2 values (ie: lack of any reading other that .45 for the most part). It did not seem to be running rich at all today either (via the sniffer test - it used to burn my eyes at times), but I did get it to start missing when I put it in second and held it at about 2500rpm (which, incidently, didn't seem to register in winaldl, but that's what my tach said). Anyway, enjoy....

Time SENSOR:PROMID SENSOR:IAC SENSOR:Coolant Temp SENSOR:SPEED SENSOR:MAP SENSOR:RPM SENSOR:TPS SENSOR:INT SENSOR:O2 SENSOR:Battery Voltage SENSOR:Knock counter SENSOR:BLM SENSOR:IAT
331.8 7501 33 83.5 56 31.0 1200 6.0 128 0.455 13.6 0 128 51.4
333.0 7501 31 83.5 55 30.6 1200 6.0 128 0.451 13.6 0 128 51.4
334.2 7501 34 83.5 55 37.3 1200 7.9 128 0.455 13.6 0 128 51.4
335.4 7501 54 83.5 55 55.7 1200 19.5 128 0.455 13.6 0 128 51.4
336.6 7501 128 83.5 58 89.7 2075 31.1 128 0.451 13.6 0 128 51.4
337.8 7501 113 83.5 63 46.1 1500 3.6 128 0.455 13.7 0 128 51.4
339.0 7501 66 83.5 61 23.6 1300 1.2 128 0.451 13.8 0 128 51.4
340.2 7501 39 83.5 60 21.4 1225 1.2 128 0.451 13.6 0 128 51.4
341.4 7501 31 83.5 58 21.1 1150 1.2 128 0.451 13.6 0 128 51.4
342.5 7501 31 83.5 56 21.8 1075 1.2 128 0.451 13.7 0 128 51.4
343.7 7501 62 83.5 55 66.4 1675 18.6 128 0.451 13.5 0 129 51.4
344.9 7501 118 83.5 56 62.0 1700 15.2 128 0.446 13.5 0 128 51.4
346.1 7501 93 83.5 58 28.4 1250 1.2 128 0.455 13.7 0 128 51.4
347.3 7501 54 83.5 56 24.4 1225 2.1 128 0.451 13.7 0 128 51.4
348.5 7501 39 83.5 55 37.7 1325 8.9 128 0.451 13.5 0 128 51.4
349.7 7501 86 83.5 56 64.2 1300 14.7 129 0.451 13.5 0 128 51.4
350.9 7501 85 83.5 58 59.4 1250 11.8 132 0.451 13.5 0 129 51.4
352.0 7501 77 83.5 60 57.2 1300 11.8 134 0.451 13.6 0 131 51.4
353.2 7501 72 83.5 61 51.3 1325 10.8 128 0.451 13.6 0 128 51.4
354.4 7501 55 83.5 61 23.3 1300 2.6 128 0.451 13.8 0 128 51.4
355.6 7501 33 83.5 61 21.8 1275 3.6 128 0.451 13.7 0 128 51.4
356.8 7501 88 83.5 61 65.3 1700 17.6 128 0.451 13.5 0 128 51.4
358.0 7501 91 83.5 64 31.4 1375 2.1 128 0.451 13.6 0 128 51.4
359.2 7501 52 83.5 64 21.4 1300 1.2 128 0.451 13.7 0 128 51.4
360.4 7501 32 83.5 64 19.9 1275 1.2 128 0.451 13.7 0 128 51.4
361.6 7501 31 83.5 64 19.6 1275 1.2 128 0.451 13.7 0 128 51.4
362.7 7501 31 83.5 63 19.9 1225 1.2 128 0.451 13.7 0 128 51.4
363.9 7501 31 83.5 63 19.6 1250 1.2 128 0.451 13.7 0 128 51.4
365.1 7501 31 83.5 63 19.9 1250 1.2 128 0.451 13.6 0 128 51.4
366.3 7501 31 83.5 61 19.9 1225 1.2 128 0.451 13.7 0 128 51.9
367.5 7501 31 83.5 61 20.7 1225 1.2 128 0.451 13.6 0 128 51.9
368.7 7501 42 83.5 61 33.6 1425 8.4 128 0.451 13.6 0 128 51.9
369.9 7501 32 83.5 61 19.9 1200 1.2 128 0.451 13.6 0 128 51.9
371.1 7501 31 83.5 61 20.3 1200 1.2 128 0.442 13.6 0 128 51.9
372.2 7501 31 83.5 61 20.3 1200 1.2 128 0.451 13.6 0 128 51.9
373.4 7501 31 83.5 61 20.3 1225 1.2 128 0.451 13.4 0 128 51.9
374.6 7501 31 83.5 61 19.9 1200 1.2 128 0.451 13.5 0 128 51.9
375.8 7501 31 83.5 61 20.3 1175 2.1 128 0.451 13.7 0 128 51.9
377.0 7501 70 83.5 61 45.8 1500 11.8 128 0.451 13.6 0 128 51.9
378.2 7501 68 83.5 63 47.3 1350 11.3 128 0.451 13.5 0 128 51.4
379.4 7501 60 83.5 64 35.4 1425 7.9 128 0.451 13.6 0 128 51.4
380.6 7501 46 83.5 64 23.3 1375 3.6 128 0.451 13.6 0 128 51.4
381.8 7501 31 83.5 64 22.2 1350 7.5 128 0.451 13.6 0 128 51.4
383.0 7501 60 83.5 64 43.6 1375 8.9 128 0.451 13.6 0 128 51.4
384.1 7501 45 82.9 63 26.2 1375 5.0 128 0.451 13.7 0 128 51.4
385.3 7501 32 82.9 63 24.7 1350 5.0 128 0.451 13.7 0 128 51.4
386.5 7501 31 82.9 61 25.1 1325 5.0 128 0.451 13.7 0 128 51.4
387.7 7501 31 82.9 61 25.5 1325 5.0 128 0.451 13.6 0 128 51.4
388.9 7501 31 82.9 60 25.9 1275 5.0 128 0.451 13.6 0 128 51.4
390.1 7501 31 82.9 58 24.0 1225 3.1 128 0.451 13.8 0 128 51.4
391.3 7501 31 82.9 56 20.7 1125 1.2 128 0.451 13.6 0 128 51.4
392.5 7501 31 82.9 55 22.2 1050 1.2 128 0.451 13.5 0 128 51.4
393.7 7501 31 82.9 50 23.3 950 1.2 128 0.451 13.6 0 128 51.4
394.8 7501 31 82.9 47 24.4 900 1.2 128 0.451 13.5 0 128 51.4
396.0 7501 31 82.9 40 26.2 850 1.2 128 0.451 13.5 0 128 51.4
397.2 7501 31 82.9 35 27.7 775 1.2 128 0.451 13.5 0 128 51.4
398.4 7501 31 82.9 32 29.9 700 1.2 128 0.451 13.6 0 128 51.4
399.6 7501 31 82.9 27 32.1 650 1.2 128 0.451 13.6 0 128 51.4
400.8 7501 31 82.9 23 28.1 775 1.2 128 0.451 13.6 0 128 51.4
402.0 7501 31 82.9 18 31.8 650 1.2 128 0.451 13.6 0 128 51.4
403.2 7501 31 82.9 11 36.9 575 1.2 128 0.451 13.6 0 128 51.4
404.4 7501 29 82.9 6 36.6 575 1.2 128 0.451 13.6 0 128 51.4
405.5 7501 25 82.9 5 36.2 550 1.2 128 0.451 13.6 0 128 51.9
406.7 7501 23 82.9 0 36.2 550 1.2 128 0.451 13.5 0 128 51.9
407.9 7501 23 82.9 0 36.2 525 1.2 128 0.451 13.5 0 128 51.9
409.1 7501 23 82.9 0 36.2 550 1.2 128 0.451 13.5 0 128 51.9
410.3 7501 23 82.9 0 36.6 525 1.2 128 0.451 13.6 0 128 51.9
411.5 7501 23 82.9 0 36.6 550 1.2 128 0.451 13.5 0 128 51.9
412.7 7501 23 82.9 0 35.4 550 1.2 128 0.451 13.6 0 128 51.9
413.9 7501 23 82.9 0 36.2 525 1.2 128 0.451 13.5 0 128 51.9
415.0 7501 23 82.9 0 36.2 550 1.2 128 0.451 13.7 0 131 51.9
416.2 7501 78 82.9 2 56.8 1375 13.3 128 0.451 13.6 0 131 51.4
417.4 7501 82 82.9 13 61.3 1575 18.1 128 0.455 13.6 0 129 51.4
418.6 7501 126 82.9 24 74.2 1700 26.8 128 0.455 13.6 0 129 51.4
419.8 7501 128 82.9 34 77.9 1975 27.3 128 0.362 13.5 0 129 51.4
421.0 7501 128 82.9 43 79.4 2000 29.2 131 0.451 13.5 0 129 51.4
422.2 7501 117 82.9 48 49.8 1125 6.0 128 0.455 13.5 0 128 51.4
423.4 7501 74 82.9 50 44.7 1100 7.0 128 0.455 13.6 0 128 51.4
424.6 7501 53 82.9 51 40.2 1100 6.5 128 0.451 13.5 0 128 51.4
425.7 7501 42 82.9 51 52.8 1125 12.8 128 0.451 13.6 0 131 51.4
426.9 7501 67 82.9 53 47.3 1175 8.4 128 0.451 13.5 0 128 51.4
428.1 7501 54 82.9 53 42.8 1175 7.5 128 0.451 13.5 0 128 51.4
429.3 7501 46 82.9 55 35.1 1175 5.5 128 0.451 13.5 0 128 51.4
430.5 7501 35 82.9 53 32.5 1175 6.0 128 0.451 13.5 0 128 51.4
431.7 7501 31 82.9 53 33.2 1150 6.0 128 0.451 13.7 0 128 51.4
432.9 7501 31 83.5 51 22.9 1000 1.2 128 0.451 13.7 0 128 51.4
434.1 7501 31 83.5 50 20.7 1625 6.0 128 0.451 13.7 0 128 51.4
435.3 7501 64 83.5 48 42.1 1800 13.3 128 0.455 13.6 0 129 51.4
436.4 7501 108 83.5 51 58.3 1875 13.7 128 0.451 13.5 0 128 51.4
437.6 7501 84 83.5 53 29.5 1875 7.9 128 0.451 13.6 0 128 51.4
438.8 7501 64 83.5 53 30.6 1875 8.9 128 0.451 13.6 0 128 51.4
440.0 7501 53 83.5 53 16.6 1925 1.2 128 0.451 13.6 0 128 51.4
441.2 7501 32 83.5 53 16.6 1725 1.2 128 0.451 13.6 0 128 51.4
442.4 7501 31 83.5 51 16.6 1650 1.2 128 0.451 13.6 0 128 51.9
443.6 7501 31 83.5 50 17.0 1600 1.2 128 0.451 13.8 0 128 51.9
444.8 7501 34 83.5 48 24.4 1700 7.0 128 0.451 13.6 0 128 51.9
445.9 7501 64 83.5 50 35.8 1850 10.8 128 0.451 13.6 0 128 51.9
447.1 7501 78 83.5 51 42.8 1825 12.8 128 0.455 13.6 0 128 51.9
448.3 7501 78 83.5 55 41.4 1875 12.8 128 0.451 13.5 0 128 51.9
449.5 7501 78 83.5 56 39.5 2000 12.8 128 0.455 13.6 0 128 51.4
450.7 7501 64 82.9 56 17.0 1950 1.2 128 0.451 13.7 0 128 51.4
451.9 7501 38 82.9 55 16.6 1850 1.2 128 0.451 13.7 0 128 51.9
453.1 7501 31 82.9 53 21.8 1100 1.2 128 0.451 13.7 0 128 51.9
454.3 7501 31 82.9 53 21.8 1050 1.2 128 0.451 13.6 0 128 51.9
455.5 7501 31 82.9 51 22.5 1000 1.2 128 0.451 13.5 0 128 51.9
456.6 7501 31 82.9 48 23.3 975 1.2 128 0.451 13.8 0 128 51.9
457.8 7501 31 82.9 48 33.2 1125 1.7 128 0.451 13.7 0 128 51.9
459.0 7501 31 83.5 47 24.4 900 1.2 128 0.451 13.7 0 128 51.9
460.2 7501 31 82.9 47 25.1 900 1.2 128 0.446 13.8 0 128 51.9
461.4 7501 31 83.5 45 23.3 925 1.2 128 0.451 13.8 0 128 51.9
462.6 7501 31 83.5 43 25.9 850 1.2 128 0.451 13.7 0 128 51.9
463.8 7501 31 83.5 43 26.2 875 1.2 128 0.451 13.6 0 128 51.9
465.0 7501 31 83.5 42 27.3 775 1.2 128 0.451 13.5 0 128 51.9
466.2 7501 31 83.5 35 29.5 725 1.2 128 0.451 13.5 0 128 51.9
467.3 7501 31 83.5 27 32.9 600 1.2 128 0.451 13.5 0 128 51.9
468.5 7501 48 83.5 23 52.1 1150 11.3 128 0.455 13.6 0 131 51.9
469.7 7501 114 83.5 27 67.2 1650 17.6 128 0.446 13.6 0 129 51.9
470.9 7501 122 83.5 35 66.8 1775 18.6 128 0.451 13.6 0 129 51.9
472.1 7501 122 83.5 42 69.0 1625 18.6 128 0.429 13.6 0 129 51.9
473.3 7501 113 83.5 47 48.0 1200 7.0 128 0.455 13.6 0 128 51.9
474.5 7501 77 83.5 48 41.4 1200 7.0 128 0.455 13.7 0 128 51.9
475.7 7501 48 83.5 50 25.1 1050 1.2 128 0.451 13.7 0 128 51.9
476.8 7501 31 83.5 48 23.6 975 1.2 128 0.451 13.6 0 128 51.9
478.0 7501 31 83.5 47 24.0 950 1.2 128 0.442 13.4 0 128 51.9
479.2 7501 31 83.5 42 26.2 850 1.2 128 0.451 13.2 0 128 51.9
480.4 7501 31 83.5 35 28.1 750 1.2 128 0.451 13.6 0 128 51.9
481.6 7501 31 83.5 27 34.0 625 1.2 128 0.451 13.1 0 128 51.9
482.8 7501 40 83.5 19 34.3 675 1.2 128 0.451 13.7 0 128 51.9
484.0 7501 37 83.5 18 54.3 1050 11.3 128 0.455 13.3 0 131 51.9
485.2 7501 108 83.5 23 65.7 1600 16.6 128 0.442 13.6 0 131 51.9
486.4 7501 108 83.5 31 65.0 1650 16.6 128 0.451 13.6 0 129 51.9
487.6 7501 108 83.5 35 62.8 1725 16.6 128 0.438 13.6 0 129 51.9
488.7 7501 108 83.5 40 65.7 1625 16.6 128 0.455 13.6 0 131 51.9
489.9 7501 97 83.5 43 50.2 1200 8.9 128 0.455 13.6 0 128 51.4
491.1 7501 73 83.5 45 45.0 1225 8.4 128 0.455 13.7 0 128 51.9
492.3 7501 59 82.9 45 42.1 1200 8.4 128 0.451 13.7 0 128 51.9
493.5 7501 52 82.9 45 42.5 1200 8.4 128 0.455 13.6 0 128 51.9
494.7 7501 49 82.9 45 42.1 1200 8.4 128 0.455 13.6 0 128 51.9
495.9 7501 45 82.9 45 38.0 1150 7.0 128 0.455 13.7 0 128 51.9
497.1 7501 39 82.9 47 37.3 1125 7.0 128 0.451 13.7 0 128 51.9
498.2 7501 37 82.9 45 36.9 1125 7.0 128 0.455 13.7 0 128 51.9
499.4 7501 31 82.9 45 25.1 925 1.2 128 0.451 13.8 0 128 51.9
500.6 7501 31 82.9 45 25.5 875 1.2 128 0.451 13.7 0 128 51.9
501.8 7501 31 82.9 43 25.5 875 1.2 128 0.442 13.8 0 128 51.9
503.0 7501 31 82.9 42 26.6 875 1.2 128 0.451 13.6 0 128 51.9
504.2 7501 31 82.9 37 28.1 775 1.2 128 0.451 13.2 0 128 51.9
505.4 7501 31 82.9 32 29.9 700 1.2 128 0.446 13.2 0 128 51.9
506.6 7501 31 82.9 29 32.9 650 1.2 128 0.451 13.5 0 128 51.9
507.8 7501 31 82.9 24 33.6 725 1.2 128 0.451 13.2 0 128 51.9
508.9 7501 31 82.9 14 35.4 575 1.2 128 0.451 13.5 0 128 51.9
510.1 7501 31 82.9 8 37.7 550 1.2 128 0.451 13.1 0 128 52.4
511.3 7501 28 82.9 0 41.4 575 6.0 128 0.451 13.2 0 128 52.4
512.5 7501 31 82.9 2 38.4 550 1.2 128 0.451 13.8 0 128 52.4
513.7 7501 26 82.9 5 37.3 575 1.7 128 0.451 13.4 0 131 52.4
514.9 7501 86 82.9 5 58.3 1425 13.3 128 0.451 13.7 0 128 52.4
516.1 7501 59 82.9 16 27.7 1025 1.2 128 0.451 13.4 0 128 52.4
517.3 7501 31 82.9 16 39.1 775 13.3 128 0.455 13.6 0 131 52.4
518.5 7501 96 82.9 18 67.2 1700 18.1 128 0.442 13.6 0 129 51.9
519.6 7501 121 82.9 26 69.8 1650 19.0 128 0.451 13.6 0 129 52.4
520.8 7501 126 82.9 32 69.0 1725 19.5 128 0.451 13.6 0 129 52.4
522.0 7501 128 82.3 39 85.3 1900 33.0 128 0.455 13.5 0 129 52.4
523.2 7501 128 82.3 47 76.0 1850 21.9 128 0.451 13.5 0 129 52.4
524.4 7501 119 82.3 50 58.0 1475 12.3 128 0.455 13.5 0 131 52.4
525.6 7501 86 82.3 51 36.6 1125 1.2 128 0.451 13.7 0 128 52.4
526.8 7501 50 82.3 51 25.1 1050 1.2 128 0.451 13.7 0 128 52.4
528.0 7501 31 82.3 50 23.6 1000 1.2 128 0.451 13.7 0 128 52.4
529.2 7501 31 82.3 48 23.6 1000 1.2 128 0.451 13.7 0 128 52.4
530.3 7501 31 82.3 48 23.6 975 1.7 128 0.451 13.7 0 128 52.4
531.5 7501 82 82.3 48 54.6 1475 12.8 128 0.451 13.6 0 128 52.4
532.7 7501 66 82.3 50 33.2 1050 2.1 128 0.451 13.7 0 128 52.4
533.9 7501 40 82.3 50 24.4 1050 2.1 128 0.451 13.6 0 128 52.4
535.1 7501 31 82.3 50 24.0 1025 2.1 128 0.451 13.7 0 128 52.4
536.3 7501 31 82.3 48 24.7 1025 2.1 128 0.451 13.7 0 128 52.4
537.5 7501 48 82.3 48 41.0 1225 8.9 128 0.451 13.6 0 128 52.4
538.7 7501 48 82.3 50 43.2 1100 8.9 128 0.451 13.6 0 128 52.4
539.9 7501 44 82.3 51 32.9 1100 5.0 128 0.451 13.6 0 128 52.4
541.0 7501 32 82.3 51 30.6 1100 4.6 128 0.451 13.6 0 128 52.4