92 corvette failed emissions???
Thread Starter
Intermediate
Joined: Jan 2018
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92 corvette failed emissions???
I got my car running good (or so I thought) I went to get emissions and I failed terribly. I got 10.3 on HC and the limit is 1.5 I got 47.4 on CO and the limit is 15!! I did pass CO2 and NOx tho. I’ve done some research and this basically means the car is running rich corect? And unburned fuel? The graph for HC was bad as soon as they started recording it immediately the graph shot up and stayed there no matter the engine speed so something is definitely wrong. I just don’t know what it sounds like there might be a slight Miss fire as well. Anything that could help would be great iv replaced the fuel pressure regulator and map sensor. What else would you guys recommend ? have you experienced this before?
Race Director
Joined: Sep 2001
Posts: 14,676
Likes: 751
From: NEwhere Ohio
The 92 and 93’s definitely idle nastier than the MAF and sequential cars.
the o2 sensors are freakkng KEY to making these cars run right.
IMHO the Bosch o2’s are inferior to oem quality ac delco o2’s.
i got insane lucky at summit racing equip
last summer and found some new old stock 1996 boxes of ac delco heated o2 sensors with made in usa labelling. I converted mine over to heated since i have headers.
it did clean up my idle a little bit and put my blm numbers closer to 128 (still split though ). I have a 224/236 cam so its more aggressive than stock
im assuming you still have cats and other emissions equipment and a stock tune.
a bad optispark / plugs / wires could also cause unburned fuel problems.
the o2 sensors are freakkng KEY to making these cars run right.
IMHO the Bosch o2’s are inferior to oem quality ac delco o2’s.
i got insane lucky at summit racing equip
last summer and found some new old stock 1996 boxes of ac delco heated o2 sensors with made in usa labelling. I converted mine over to heated since i have headers.
it did clean up my idle a little bit and put my blm numbers closer to 128 (still split though ). I have a 224/236 cam so its more aggressive than stock
im assuming you still have cats and other emissions equipment and a stock tune.
a bad optispark / plugs / wires could also cause unburned fuel problems.
Last edited by dizwiz24; Mar 26, 2018 at 07:29 PM.
Thread Starter
Intermediate
Joined: Jan 2018
Posts: 48
Likes: 0
The 92 and 93’s definitely idle nastier than the MAF and sequential cars.
the o2 sensors are freakkng KEY to making these cars run right.
IMHO the Bosch o2’s are inferior to oem quality ac delco o2’s.
i got insane lucky at summit racing equip
last summer and found some new old stock 1996 boxes of ac delco heated o2 sensors with made in usa labelling. I converted mine over to heated since i have headers.
it did clean up my idle a little bit and put my blm numbers closer to 128 (still split though ). I have a 224/236 cam so its more aggressive than stock
im assuming you still have cats and other emissions equipment and a stock tune.
a bad optispark / plugs / wires could also cause unburned fuel problems.
the o2 sensors are freakkng KEY to making these cars run right.
IMHO the Bosch o2’s are inferior to oem quality ac delco o2’s.
i got insane lucky at summit racing equip
last summer and found some new old stock 1996 boxes of ac delco heated o2 sensors with made in usa labelling. I converted mine over to heated since i have headers.
it did clean up my idle a little bit and put my blm numbers closer to 128 (still split though ). I have a 224/236 cam so its more aggressive than stock
im assuming you still have cats and other emissions equipment and a stock tune.
a bad optispark / plugs / wires could also cause unburned fuel problems.
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
Actually, that would be an incomplete, at best, misleading at worst test. All it says is the coil is operating or not and not the pintle is spraying at spec or not. Cut off the bottom and it will ohm out at whatever it was before the cut. I really wouldn't change one any more than one shoe that got worn. Change it as a set.
Thread Starter
Intermediate
Joined: Jan 2018
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Actually, that would be an incomplete, at best, misleading at worst test. All it says is the coil is operating or not and not the pintle is spraying at spec or not. Cut off the bottom and it will ohm out at whatever it was before the cut. I really wouldn't change one any more than one shoe that got worn. Change it as a set.
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
Get a reman set which is about $200 from FIC then or some junkyard to replace that one if you are selling it soon.
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Pro
Joined: Jan 2003
Posts: 706
Likes: 47
From: Denver Colorado
Any codes in your history? I assume you do not have an illuminated CEL (check engine light) or that would have failed you. Was it good and hot when tested or had you waited in one of those interminable lines at the testing station? The Clean Air Colorado testing always goes better if you can come in hot.
Thread Starter
Intermediate
Joined: Jan 2018
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Any codes in your history? I assume you do not have an illuminated CEL (check engine light) or that would have failed you. Was it good and hot when tested or had you waited in one of those interminable lines at the testing station? The Clean Air Colorado testing always goes better if you can come in hot.
yes i I made sure the car was up to temp and it comes on intermittently now? I’m pretty sure it’s the Evap connector that connects the egr valve to a vaccume
Thread Starter
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moduel 4:H43
moduel 9:——
Pro
Joined: Jan 2003
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From: Denver Colorado
Well 72 is "Gear selector switch" 74 is not in my references and 43 is a Knock Sensor (KS) or Electronic Spark Control Circuit (ESC) fail.
Thread Starter
Intermediate
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so what do I do about those how can I test them? 72 and 74 are for the CCM not the ECM which is the led dimming circuit or what not. Can I change the knock sensor with out draining the coolant.
Pro
Joined: Jan 2003
Posts: 706
Likes: 47
From: Denver Colorado
The knock sensor can not be changed without opening up the cooling system. It threads into the water jacket using the old block drain port. Often this is full of rust and corrosion but, it hooks up to the water jacket. I'd drain the system prior to changing it or at least have a bucket ready to catch the coolant if I was going to try it "on the fly".
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
The knock sensor can not be changed without opening up the cooling system. It threads into the water jacket using the old block drain port. Often this is full of rust and corrosion but, it hooks up to the water jacket. I'd drain the system prior to changing it or at least have a bucket ready to catch the coolant if I was going to try it "on the fly".
Thread Starter
Intermediate
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I'd pay someone to do it I have dogs and don't want to have coolant on the floor I have a feeling that if it spills on driveway and goes into the sewer my neighbors may not be impressed I'd make arrangements to have the KS pulled and a garden hose back flush that port and the other side flushed Bottom line is NIMBY
Burning Brakes
Joined: Feb 2013
Posts: 769
Likes: 95
From: Central Pennsylvania
Thank God Pennsylvania doesn’t require anything more than a visual on C4’s. They do check the gas gas cap though. In fact, less than 5 K miles a year, they are completely exempt. Even with a CES light on.
( actually 2 of mine have Antique tags and don’t even require State Inspection at all )
Probably the only good thing about “ Taxylvania”
( actually 2 of mine have Antique tags and don’t even require State Inspection at all )
Probably the only good thing about “ Taxylvania”
Last edited by skyhawk50; Mar 28, 2018 at 11:29 PM.
Team Owner
Joined: Jul 2004
Posts: 28,462
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From: Hartford WI
NIMBY?
And iv never been about paying someone to do stuff, I’m a DIY guy and would rather learn once and screw up then pay someone double to triple what it would cost me to do it. The shop I work at would let me do it but I don’t have the most time to stay there after work being a full time student. And they sent open on weekends and are busy with projects so weekends are my time to learn stuff. I know how to do this all relatively iv watched people do it but I didn’t want to do a full coolant flush and what not but it’s fine I have to. Just want to pass emissions or say I can. It’s a lot harder to sell a car when it doesn’t pass emissions
I learned I don't want coolant on the driveway. I learned I don't want the wife asking me for weeks "Are you sure you washed everything off?" when she takes the dogs out. I learned I don't want my neighbors seeing me flush stuff down the sewer. I also learned that this is 2018 and almost everyone has a cell phone and camera. If I worked in a shop, I'd DIY if they let me.
Your code 74. Have you got the stock radio and if so, does it dim display? Some have thought that might be the issue.
https://tech.corvettecentral.com/201...trouble-codes/
Team Owner
Joined: Jul 2004
Posts: 28,462
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From: Hartford WI
https://www.corvetteactioncenter.com...ule-9-h72.html
Might be worth looking at. It does have something pertaining to your year and code
Might be worth looking at. It does have something pertaining to your year and code