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Failed emissions need advice

T

tdr1919

Guest
Well, I thought for sure I would pass the NY inspection this year, the new MAP cleared all the engine codes, I did the brakes all the lights are working, feeling real confident. Here on LI fewer & fewer stations are inspecting pre- OBII cars, it my regular guy, won't even repair his system this year sooooo. I passed all the safety regulations but failed emissions, said my CO was double the allowable number. my O2 sensors were good. The mechanic was kind enough to run some diags before I got there.
fuel pressure - 43lb
vacuum - 20 hg
fuel pressure leak down was about a minute (failed).
the timing was 12 deg. should be 6 deg
spark plug gap was at .45 should be .35
I am running plus gas not high test.
All of the plugs looked good not like they are running rich.

Where should I go from here?

Tom
 

gmboileau

Active member
Joined
May 20, 2005
Messages
26
Location
Toronto
Corvette
1990 Red Convertible
Hi Tom
The best way to diagnose an emissions problem is to use a scanner to look at the data sent by the various sensors to the computer and compare it to the normal values. For example,in your case given the quick fuel pressure leak down it could be a faulty injector(s) which would cause a rich condition(Code 45) and would be validated by integrator and block learn values lower than normal. This is only one possibility but without the data you can spend a lot of money guessing as to what the problem is and replacing good parts.

Gary
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Some of the findings could do it, albeit, not sure if they would all account for a double-the-reading on the CO.

The factory timing settings are so due to the emission requirements, and it is not for improved performance. So the timing back to 6 deg BTDC is a start.

With the plug gaps at 0.045" instead of 0.035" could contribute to an increased percentage of misses (unless you have an after-market multi spark distributor added). The increased percentage on misses could be increasing the amount of un-burned fumes mixing it up with the burned gases.

20 Hg-In of vacuum seem pretty healthy -compare this against factory vacuum requirements to see if it is normal or not. Your added timing could be causing the 20 Hg-In readings (in other words, perhaps 18 or 19 is closer to normal).

GerryLP:cool
 
T

tdr1919

Guest
Hi Tom
The best way to diagnose an emissions problem is to use a scanner to look at the data sent by the various sensors to the computer and compare it to the normal values. For example,in your case given the quick fuel pressure leak down it could be a faulty injector(s) which would cause a rich condition(Code 45) and would be validated by integrator and block learn values lower than normal. This is only one possibility but without the data you can spend a lot of money guessing as to what the problem is and replacing good parts.

Gary

Gary, I spent the afternoon looking for scanners, and I found a few PC software programs for ALDL interfaces. I was wondering if this is what you are using and what you would recommend. My laptop does not have an RS-232 port, I would have to get a USB cable, most of what I saw (freeware) were older and configure for RS 232. Too bad, with my PC, because the RS 232 cable is pretty easy to make. Your ideas?
Thanks,
Tom
 

gmboileau

Active member
Joined
May 20, 2005
Messages
26
Location
Toronto
Corvette
1990 Red Convertible
Hi Tom
The equipment I used when I was going through the diagnosing process with my car which had an intermittent check engine light was a SnapOn Mt 2500 scanner hooked to an old laptop which had the glitch snitch software from SnapOn installed. I worked in a vocational school which had all this equipment so I was able to borrow it.

The Scanner will show the data but the laptop makes it easier to see all the data at once and in a graphical format. The glitch snitch software will point out any momentary abnormal data values that may be happening. For example a corroded connector on the temperature sensor could tell the computer that the car is cold when it’s hot so the computer responds by increasing the injector pulse width and thus more unneeded fuel and possibly a failed emissions test. Any decent shop will have all this equipment and a guy who can look at it and be able to interpret the data.

I haven’t used any of the freeware but if it presents the data on a laptop that’s all you need. You can get a USB to Serial Port Cable at Radio Shack or Future Shop. I have one for my GPS and it works fine. You could also pick up an old laptop with a RS 232 port for less than the price of the cable. The laptop I used is still running Windows 95 and works just fine for my auto applications. The car computer and the laptop are a technology match. I believe the key to your problem is finding out what data inputs the computer is responding to and looking for abnormal values. After saying that I assume that you done a careful visual check looking for such things as cracked or split vacuum lines, loose or damaged connectors ect.

Cheers
Gary
 

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