Guest HuevosRanchero Posted May 26, 2015 Share Posted May 26, 2015 As some may have noticed, after fixing some leaking vacuum lines I seemed to create an idle issue that resembled a problem with the Idle control valve. Ran great but once in closed loop mode...stopping was iffy as to whether the car would stall. The more I fixed ..the worse it got... Cleaned ICV (initially seemed to help), MAF, no help...glad I didnt panic buy replacements (good to be the less stress inducing backup car). The one thing that helped was unplugging the vacuum to the fuel pressure regulator. Would idle fairly normally. Note..I was able to manipulate the ICV and MAF so I knew they were functioning...but I REALLY need to get familiar with the onboard diagnostics. SO...after all that...I wracked my brain....WHY does unplugging the vacuum to the fuel regulator make the car run well? Well because it was getting more fuel instead of tapering off like it should when coming to a stop (hence with the vacuum leaks allowed the car to run semi normally while of course the environmental controls were dead. SO ..I theorized the computer was ordering the ICV open enough to allow the car to function (still with some idle diving at stop but not enough to stall) So I unplugged the oxygen sensor...and holy cats the idle diving stopped. Keep in mind STILL no Check engine or codes. Replaced what appears to be an original unit with a new Bosch and sweet success! Just sharing the happiness, I'll get better as time goes on. Link to comment Share on other sites More sharing options...
Ronnie Posted May 26, 2015 Share Posted May 26, 2015 As I've said before, changing the O2 sensor should be part of routine maintenance. I change them at 50,000 miles OR as soon as I get a used car if I don't have a history of the maintenance that has been done. Even if the car doesn't have the stalling problems like yours, an old dirty O2 sensor can cause poor performance and poor gas mileage. Don't rule out a new O2 sensor as the cause of a poor running engine either. I've been down that road to. Link to comment Share on other sites More sharing options...
Guest HuevosRanchero Posted May 26, 2015 Share Posted May 26, 2015 As I've said before, changing the O2 sensor should be part of routine maintenance. I change them at 50,000 miles OR as soon as I get a used car if I don't have a history of the maintenance that has been done. Even if the car doesn't have the stalling problems like yours, an old dirty O2 sensor can cause poor performance and poor gas mileage. Don't rule out a new O2 sensor as the cause of a poor running engine either. I've been down that road to. Yep...am going to probably change the O2 sensors in the other cars in the family just because.....I can and it's cheap and they are all high mileage....etc. Link to comment Share on other sites More sharing options...
padgett Posted May 27, 2015 Share Posted May 27, 2015 In general an O2 sensor can have any value except zero so does not set a code unless shorted to ground. It can cause the TCC to unlock if transitions stop. Can usually see a bad O2 in ED18 "cross counts". May be 1 or 2 at idle but should be over 6 when cruising. Car does need to be warmed up to work. ps OEM was an AC unit and definately not a Bosch. They make it hard to remove the #6 plug. Link to comment Share on other sites More sharing options...
Guest HuevosRanchero Posted May 27, 2015 Share Posted May 27, 2015 In general an O2 sensor can have any value except zero so does not set a code unless shorted to ground. It can cause the TCC to unlock if transitions stop. Can usually see a bad O2 in ED18 "cross counts". May be 1 or 2 at idle but should be over 6 when cruising. Car does need to be warmed up to work. ps OEM was an AC unit and definately not a Bosch. They make it hard to remove the #6 plug.yep I definitely need practice with the diagnostic capabilities of this car. Link to comment Share on other sites More sharing options...
2seater Posted May 27, 2015 Share Posted May 27, 2015 When you get more comfortable with the diagnostics, could you post some of the readings from the sensors? I am glad your car is happy now and I find it very interesting that an O2 sensor would cause actual stalling. I will have to look into a problem child I have now to see if the O2 will make any difference. I would have said the O2 just can't cause this sort of issue, but learned some things just don't follow the rules. Link to comment Share on other sites More sharing options...
DAVES89 Posted May 27, 2015 Share Posted May 27, 2015 I had a problem where my Red was "bucking". It would idle fine just give me a bucking feeling while driving. If I floored it, it would run great until I left off on the gas. I would run in Drive [so it wouldn't go in overdrive] and was swapping MAF sensors trying to find the problem. I then swapped out the ozygen sensor and it is back to running as it should. Link to comment Share on other sites More sharing options...
Guest HuevosRanchero Posted May 28, 2015 Share Posted May 28, 2015 (edited) When you get more comfortable with the diagnostics, could you post some of the readings from the sensors? I am glad your car is happy now and I find it very interesting that an O2 sensor would cause actual stalling. I will have to look into a problem child I have now to see if the O2 will make any difference. I would have said the O2 just can't cause this sort of issue, but learned some things just don't follow the rules. I was pretty surprised myself....drove the old girl last night...sweet as she can be now. I think the readings from the sensor were erratic and causing the ICV to "stutter" causing the stall issue. ...If you are suspicious try unplugging the sensor and see if it alters or improves the problem. Just unplugging the sensor made the car idle better (with zero input the computer may have defaulted to some kind of default table?) Edited May 28, 2015 by HuevosRanchero (see edit history) Link to comment Share on other sites More sharing options...
padgett Posted May 28, 2015 Share Posted May 28, 2015 Unplugging the O2 sensor will force the car to stay in "open loop" (e.g. before warmed up) and will use very conservative maps. MPG will head for the basement. Link to comment Share on other sites More sharing options...
2seater Posted May 28, 2015 Share Posted May 28, 2015 Keep us posted. It sounds like Dave had a similar experience, so there is certainly something to this cause. Interesting find. Thanks. Link to comment Share on other sites More sharing options...
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