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1993 deville 4.9L engine
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4 Posts
Discussion Starter #1
Hey there! I'm wondering why my '93 DeVille (4.9L) failed an emissions test today. The test was done in Toronto, Canada.

It only failed one thing on the test - the HC ppm while idle. The limit is 200, reading was 248, so it failed kind of badly. The HC ppm was fine during the speed test.

Could somebody kindly make a list of potential parts and problems that I may need to check? I used search, read a few threads and found them of limited help. I replaced EGR vacuum solenoid hose (from EGR solenoid to EGR). Spark plugs, distributor cap and rotor are all new.

I used 87-Octane fuel (which is the worst quality fuel available, I'm kind of cheap) during the test. Would changing to a higher grade of fuel (such as the one it's actually supposed to be running on) help?

The car just made it 2200 miles over 3 days from Phoenix to Toronto. Everything was fine, no ECM codes. Once again, help and suggestions (and a list of parts/problems) would be HIGHLY appreciated.
 

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Super Moderator
2010 DTS
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87,543 Posts
You've been watching too many commercials. Octane rating has absolutely nothing to do with the "quality" of the fuel. You have a 4.9 and it does not have a knock sensor so it DOES require premium.

Look down the TB and see if the two EGR tubes are carboned up. If so, rod them out. Check the FPR for a leak.
 

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Registered
1993 deville 4.9L engine
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4 Posts
Discussion Starter #4
Well, I finally passed after failing twice more. I replaced the fuel injectors and the oxygen sensor after discovering they weren't working correctly (oxygen sensor wasn't doing cross counts; fuel injectors has a resistance of 6-7 ohms). HC count went down from 248 down to 70!
 
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