Can Exhaust Leak affect O2 Sensor??
02-27-2008, 12:52 AM
#31
Nordschleife Master
I was going to say the 84 doesnt have a MAF from the factory. It has the barn door.
As well a lambda system is the adjustment of the AFR to reach proper "lambda" or "stoich" it is the O2 system.
As well a lambda system is the adjustment of the AFR to reach proper "lambda" or "stoich" it is the O2 system.
02-27-2008, 08:06 AM
#32
Rennlist Member
Thanks for catching that - I've got MAF on the brain, having cleaned two from the 993 yesterday.The adjustment I referred Dwayne to is the allan headed set screw which controls the cross section size of the bypass passage around the 'barn door' for unmetered air.
02-27-2008, 09:06 AM
#33
Dwayne,
I suspect that the function of the idle microswitch is to turn off the O2 system on your 84 also. Some require position adjustment. Could yours be out of adjustment?
Dennis
I suspect that the function of the idle microswitch is to turn off the O2 system on your 84 also. Some require position adjustment. Could yours be out of adjustment?
Dennis
02-27-2008, 09:43 AM
#34
Three Wheelin'
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YES...the AFM is what I will look into adjusting vice MAF after I repair the exhaust leak. I will try to keep this straight in the future. THANKS.
Dennis,
When I tested the idle microswitch, it did not have any affect on idle in terms of ignoring O2 inputs. As I understand it, the idle microswitch is used by the computer to shut off fuel injector pulses (effectively shutting off fuel) when the car is coasting (accelerator at rest) and engine RPM is above about 1200. When the RPMs dip below 1200 and the idle microswitch circuit is closed (i.e., accelerator at rest), the computer turns injectors on again. Of course, anytime the idle microswitch circuit is open (accelerator pedal depressed) the injectors are on. I believe this was supposed to be a fuel/emissions saving feature (i.e., why expend fuel/emissions when coasting down from high speeds - makes sense, anyway). If my understanding is incorrect, please help - I'm still learning. THANKS!
When I tested the idle microswitch, it did not have any affect on idle in terms of ignoring O2 inputs. As I understand it, the idle microswitch is used by the computer to shut off fuel injector pulses (effectively shutting off fuel) when the car is coasting (accelerator at rest) and engine RPM is above about 1200. When the RPMs dip below 1200 and the idle microswitch circuit is closed (i.e., accelerator at rest), the computer turns injectors on again. Of course, anytime the idle microswitch circuit is open (accelerator pedal depressed) the injectors are on. I believe this was supposed to be a fuel/emissions saving feature (i.e., why expend fuel/emissions when coasting down from high speeds - makes sense, anyway). If my understanding is incorrect, please help - I'm still learning. THANKS!
02-27-2008, 10:04 AM
#35
Administrator - "Tyson"
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Put a decent Y collector on there with a high flow cat. Dump the factory piece.
02-27-2008, 04:32 PM
#37
Garth,
Thought I was the only one that had rebar accidentally fall into a cat. IIRC it had to fall in there 4 or 5 times before I could dislodge it with a hammer.
Dennis
Thought I was the only one that had rebar accidentally fall into a cat.
IIRC it had to fall in there 4 or 5 times before I could dislodge it with a hammer. Dennis
02-27-2008, 06:19 PM
#38
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.... strains of Brittany chirping " whoops, I've done it again" playing in the background ...
02-28-2008, 12:58 AM
#39
Three Wheelin'
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I ordered the aftermarket "Y" pipe without CAT from Roger this morning - a very nice ordering experience! I understand it is already on the way - looking forward to comparing the stock setup with the new "Y".
03-02-2008, 12:03 AM
#42
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OK....I repaired the broken welds today. First, some pics. Here's one of the "Y" arms with the heat shield dremeled off - I also saved the thin layer of insulation just under the heat shield.
In order to get at the broken weld, I had to dremel off part of the heat shield that encases the CAT. I wanted to take off enough to make it easy to work around but not too much.
Here's what the "Y" branch looks like with the shields removed and the joint exposed enough to repair the weld.
Unfortunately, I've always wanted to learn how to weld but never had the time and don't have the equipment. I also was hesitant to take it to the muffler shop in town and deal with spot welding the joint while it's in the car, then removing the assembly so it could be welded and sealed all the way around, then have to re-install in the car at the muffler shop. What I really wanted to do is just take the assembly down to the shop and have them weld it.
So I noticed that when I put the pipes back together, they fit perfectly in the broken weld and I surmised that maybe they could just clamp it like that and weld it and it would most likely fit back in without too much trouble. So that's what I did....here's the picture of one of the joints with broken weld being held in place.
The muffler shop was able to hold the joint together for the welding and they were also able to spot weld all the heat shielding back in place. Here's what it looked like when I got back from the shop...
So, I put the O2 sensor back in and re-installed the assembly.
Only a moderate amount of effort was required to get the assembly to fit back in under the car.
I started it up and the exhaust leak I was hearing before was gone!! NICE!!
However, my exhaust still sounds noticeably louder than my wife's '88. The '88 is pretty quiet, the '84 is not quiet but also not loud either. Should the '84 stock exhaust system sound as quiet as the '88 stock exhaust?? If so, I probably have another leak somehere.
....and the results of repairing the exhaust leaks on the idle and acceleration surge.......NO EFFECT!!
I still have the slight surging. Oh well....looks like I'll be checking out the AFM fuel mixture setting. But first, I think I'll play around with the vacuum some more - for some reason, I just can't let go of the vacuum as a source of this problem!!
In order to get at the broken weld, I had to dremel off part of the heat shield that encases the CAT. I wanted to take off enough to make it easy to work around but not too much.
Here's what the "Y" branch looks like with the shields removed and the joint exposed enough to repair the weld.
Unfortunately, I've always wanted to learn how to weld but never had the time and don't have the equipment. I also was hesitant to take it to the muffler shop in town and deal with spot welding the joint while it's in the car, then removing the assembly so it could be welded and sealed all the way around, then have to re-install in the car at the muffler shop. What I really wanted to do is just take the assembly down to the shop and have them weld it.
So I noticed that when I put the pipes back together, they fit perfectly in the broken weld and I surmised that maybe they could just clamp it like that and weld it and it would most likely fit back in without too much trouble. So that's what I did....here's the picture of one of the joints with broken weld being held in place.
The muffler shop was able to hold the joint together for the welding and they were also able to spot weld all the heat shielding back in place. Here's what it looked like when I got back from the shop...
So, I put the O2 sensor back in and re-installed the assembly.
Only a moderate amount of effort was required to get the assembly to fit back in under the car.
I started it up and the exhaust leak I was hearing before was gone!! NICE!!
However, my exhaust still sounds noticeably louder than my wife's '88. The '88 is pretty quiet, the '84 is not quiet but also not loud either. Should the '84 stock exhaust system sound as quiet as the '88 stock exhaust?? If so, I probably have another leak somehere.....and the results of repairing the exhaust leaks on the idle and acceleration surge.......NO EFFECT!!
I still have the slight surging. Oh well....looks like I'll be checking out the AFM fuel mixture setting. But first, I think I'll play around with the vacuum some more - for some reason, I just can't let go of the vacuum as a source of this problem!!
07-17-2009, 11:02 PM
#44
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Jason,
My temporary solution was to disconnect the O2 sensor. I've been driving it that way for several months - idles and accelerates smooth as glass. I've been wanting to get back to this issue because it's just bugging me! So last month I performed another vacuum leak test (using the pressurize method) and everything was tight. Looks like I'll be driving the car to Oregon next weekend so I thought I'd connect the O2 again and see what happens. Anyway, I suspect when I hook it back up, it will be the same as before but I'll let you know. Bottom line is I have not resolved this to my satisfaction yet. THANKS for asking!
My temporary solution was to disconnect the O2 sensor. I've been driving it that way for several months - idles and accelerates smooth as glass. I've been wanting to get back to this issue because it's just bugging me! So last month I performed another vacuum leak test (using the pressurize method) and everything was tight. Looks like I'll be driving the car to Oregon next weekend so I thought I'd connect the O2 again and see what happens. Anyway, I suspect when I hook it back up, it will be the same as before but I'll let you know. Bottom line is I have not resolved this to my satisfaction yet. THANKS for asking!