95 wont pass smog
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Joined: Jul 2002
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From: Campbell Ca
95 wont pass smog
Ok, I have run out of ideas on what could be making this car run so rich.Here is a list of what I have replaced to try and make it pass smog: Car would not start, replaced opti and water pump; car runs but very rich.Replaced the coolant temp sensor,two front o2 sensors,ignition module,fuel pressure regulator,all plugs and wires.Tested the map sensor and it was within spec.I have done a resistance test on all the injectors, as well as a fuel pressure bleed down test, the pressure remains constant.The car runs and idles fine but is just very rich. The fuel trim stays at about 128. If anyone has any insight on what could be wrong please dont hesitate to post. 
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From: Campbell Ca
Originally Posted by Timmy!
What's the fuel pressure set to? Make sure it's not too high. Check for exhaust leaks. Also, the cats could be clogged or bad.
Le Mans Master
Joined: Feb 1999
Posts: 9,938
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From: South Carolina
St. Jude Donor '03 & '05
Look at the basics, is there any check engine light? Service engine soon light? Codes. Before spendign money on any more electronics, check mechanical things that wont throw a code. A 95 OBD1 code tester is needed here, to find out if any sensor is bad to make the car run rich, before replcaeing everything. I had a broken valve spring that made the car run rich once, and the idle was a little off, but not bad. Sounds stupid, but check under the valve covers, push down on all valve springs with you r hands, they should all be about the same. But they shouldnt go down real easy.
Also, verify all your injectors are plugged into the right injector plug, as you are a sequential firing, and if your injectors are plugged into # 6 vice #4 it will run rich. Had this happen on a 96 Vette.
Check to see if the exhaust manifolds are glowing red, or the cats at night. If the cats get too hot, and melt with a rich running motor, they can get ruined, and cause severe damage to the cats, sometimes clogging them. SO, dont run it rich too long.
The cracked manifold will make the O2 sensor think it is lean, and run it richer. Seal it with JB weld, it will only hold temporarily and see how she runs. Bet it clears up.
Also, verify all your injectors are plugged into the right injector plug, as you are a sequential firing, and if your injectors are plugged into # 6 vice #4 it will run rich. Had this happen on a 96 Vette.
Check to see if the exhaust manifolds are glowing red, or the cats at night. If the cats get too hot, and melt with a rich running motor, they can get ruined, and cause severe damage to the cats, sometimes clogging them. SO, dont run it rich too long.
The cracked manifold will make the O2 sensor think it is lean, and run it richer. Seal it with JB weld, it will only hold temporarily and see how she runs. Bet it clears up.
Melting Slicks
Joined: Apr 2003
Posts: 2,150
Likes: 6
From: NS
Originally Posted by olman
That cracked manifold just may be the problem. A little too much o2 in the exhaust and the O2 sensor will fatten it up. I wouldn't bet on it sealing up. Just my thoughts.
It's probably sucking air through the crack causing the O2 sensor to detect a lean condition so it richens it up.
If you have stock exhaust (separate left and right pipes) have the exhaust analyzed on both sides of the engine. The PCM controls the engine as two separate banks. Your problem might be on one side only. If it's both sides then look for common components.
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Joined: Jul 2002
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From: Campbell Ca
Originally Posted by Timmy!
Cracked exhaust manifold or cracked manifold on the FP regulator? Either way, I would fix that first before I did anything!
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From: Campbell Ca
Finally fixed this problem child
Turned out to be a combo of things. First was a leaky fuel pressure reg,
that took out the o2 sensor.The previous owner had hollowed out the cats,replaced them and it now burns very clean and passed smog.
Thanks for all the input guys ,motor on.
Turned out to be a combo of things. First was a leaky fuel pressure reg,
that took out the o2 sensor.The previous owner had hollowed out the cats,replaced them and it now burns very clean and passed smog.
Thanks for all the input guys ,motor on.