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Sep 3, 2009, 8:33 AM
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I have a 1995 Chevy K1500 pickup which just failed emissions for a 2 speed idle test in pennsylvania. The Hydro carbons at idle were what caused it to fail
The limit was 180 ppm and my truck turned up 281ppm
I replaced the spark plugs, wires, dist. cap & rotor, pcv valve, last year.
A few weeks ago the check engine light came on and i pulled the codes and got code:
13 Open Oxygen Sensor Circuit
35 MAP Sensor (Low Sig.)
44 Oxygen Sensor Circuit (Lean Exhaust Indicated)
I replaced the upstream oxygen sensor and that turned off the check engine light.
Do you guys have any idea what else i can do to get it to pass emissions?
Thanks
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Sidom
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Sep 3, 2009, 9:05 AM
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Re: Emissions Fail
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HCs are unburned fuel. The source could come from a number of places. A Misfire, leaky injector, deluted oil, etc. Without an exhaust gas analyzer it can be tough to tell if you've solved the problem. If it's running poorly and you fix that problem then chances are you've solved your HC problem. If it's not running bad, then without the analyzer you really can't verify if you've fixed the problem or not.
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Anonymous Poster
Sep 3, 2009, 9:27 AM
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Re: Emissions Fail
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Yeah its running fine, all of the repairs i mentioned above were perform a year before the emissions test with the exception of the oxygen sensor. I mentioned this to the guy who checked the emissions on it and he said it might be the cat. con. I really don't want to have to go into replacing that since I only need the truck for about another 5 months. I was wondering if anyone had any ideas on what we could do to bring down the HCs thats pretty cheap.
I'll probally change the oil since its just about due. I know its not misfiring at all. Do you think changing the MAP sensor would help at all even though there aren't currently any codes stored in the computer?
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Sidom
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Sep 3, 2009, 9:31 AM
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Re: Emissions Fail
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It's possible you may have a bad cat. If the MAP sensor was the cause of the HCs more than likely you would have a drivability problem, if the oil was deluted with gas you should be able to smell it on the dipstick......
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Loren Champlain Sr
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Sep 3, 2009, 10:03 AM
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Re: Emissions Fail
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Sidom; Pardon my jumping in; Since the O2 replacement, you are not getting any other codes? The MAP code didn't come back? A poor signal (low vacuum) to the MAP will cause overfueling and destroy the O2 sensor and the cat. I would expect to see high CO, as well if the MAP code returns. Check engine temperature. If the engine is not getting hot enough, that can also cause a HC (and CO) failure. You should have a 195F thermostat, so the engine should be running at at least that temp, usually around 210-220F. You don't want to replace the cat, even if it IS bad, until you get the HC and CO levels under control or you will damage the new one. Again, sorry to butt in...
Loren
SW Washington
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Sep 3, 2009, 10:51 AM
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Re: Emissions Fail
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Loren: the check engine light didn't return so I'm taking that as a sign that there are no MAP codes stored in. The temperature is running about 205F. Which is how it always ran.
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Loren Champlain Sr
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Sep 3, 2009, 11:07 AM
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Re: Emissions Fail
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I don't recall you mentioning timing. I shouldn't assume things. Be sure to disconnect the EST connector, then set timing to TDC. Anything, and I mean anything, that affects complete combustion will cause a HC failure. Cap,rotor, wires, plugs, injector spray pattern, compression, ect., ect.,...Don't overlook anything. Is this the TBI type injection? Check for a vacuum leak at the base of the TBI.
Loren
SW Washington
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Sep 3, 2009, 3:40 PM
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Re: Emissions Fail
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it's TBI. I will check for vacuum leaks where you said. I'm probally also going to remove the spark plugs and see what they look like tommorow.
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Sep 5, 2009, 10:33 AM
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Re: Emissions Fail
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the spark plugs look good and i didn't see any vacuum leaks around the throttle body.
I did jump the 2 pins to pull the codes and i got a code 13 (open oxygen sensor circuit) stored in the computer.
I replaced the upstream oxygen sensor and after doing so my check engine light went off. Is there a down stream sensor on these trucks as well? or what else could be causing this?
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Anonymous Poster
Sep 6, 2009, 11:05 AM
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Re: Emissions Fail
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does anybody know what else might cause a code 13 to be stored in the computer but not turn the check engine light on? and could that be related to the excess HCs during the emissions test:
My exact emission readings were:
Mode CO % HC ppm RPM Dilution %
2 Speed Idle Limit Reading Result Limit Reading Result Reading Result Reading Result
IDLE 1.00 0.66 Pass 180 281 FAIL 653 Valid 14.6 Valid
2500 RPM 1.00 0.75 Pass 180 73 Pass 2549 Valid 14.8 Valid
As you can see there was really only 1 problem area and it was way off on the reading.
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Anonymous Poster
Sep 6, 2009, 11:22 AM
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Re: Emissions Fail
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Sorry about that, I tried to post the exact emissions readings for my truck but it didn't come out right. I'm going to try posting a picture of the results:
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Sidom
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Sep 6, 2009, 1:20 PM
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Re: Emissions Fail
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Those reading are pretty rich. I didn't realize PA had such easy standards. In CA you would've failed everything but the high idle HC reading and even that's a little high....
I would be looking at the cat..........
What'd ya think Loren? I don't think the CO would even passed DEQ either.........
(This post was edited by Sidom on Sep 6, 2009, 1:23 PM)
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