Gas mileage sucks
Thread Starter
2nd Gear
Joined: Apr 2005
Posts: 2
Likes: 0
From: ----------- California
Gas mileage sucks
New to the forum as for posting, so here goes
1991 L98
Approx. 2 mo. ago EGR tube cracked at the accordian section causing substantial air leak, had to drive it 40-50 miles home. Replaced EGR tube with new one. Car runs ok but lacking some of the pep (loss power in low rpm range (below 2k) seems ok in high range (above 2k)) from before EGR leak. Gas mileage went from 17-18 to 12.5 smells rich. Thinking O2 sensors but do'nt want to start swapping parts, too expensive. Any way to check these, also any other ideas.
Josh in CA
1991 L98
Approx. 2 mo. ago EGR tube cracked at the accordian section causing substantial air leak, had to drive it 40-50 miles home. Replaced EGR tube with new one. Car runs ok but lacking some of the pep (loss power in low rpm range (below 2k) seems ok in high range (above 2k)) from before EGR leak. Gas mileage went from 17-18 to 12.5 smells rich. Thinking O2 sensors but do'nt want to start swapping parts, too expensive. Any way to check these, also any other ideas.
Josh in CA
Team Owner
Joined: Sep 2001
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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The oxygen sensor rarely throws a code but if its this bad then it should. If there are no other SES lights then I'd first check for vacuum leaks. The cats could also be plugged, that would produce similar symptoms but you should notice some extra heat in the footwell.
There are various scanners and test tools in the catalogs that allow you to test the O2 sensor.
There are various scanners and test tools in the catalogs that allow you to test the O2 sensor.
Thread Starter
2nd Gear
Joined: Apr 2005
Posts: 2
Likes: 0
From: ----------- California
Gas Mileage Sucks
Hello again
Here is what I have checked so far
1. No codes
2. Vacuum check with gauge. Idle goes to 20 in. Hg.. 2000rpm 20.5 in. Hg.. Rev to 5000 rpm goes to 22 in. Hg.. Stays steady at 20 in. Hg., if turn on A/C climbs to 17 in. Hg. before settling back at 20 in. Hg. Steady as a rock.
3. Checked back pressure at A.I.R. inputs to manifold per service manual, back pressure reads 0-.5 psi and oscillates like crazy, seems to low.
4. Pulled plugs checked ok, reset gap from .038 to .035, all looked good except #5 looked like it got hot. Seems every car I've ever had has this problem.
5. Waiting on test kit from madvet to check O2 sensors plus about 5-6 other things.
Going to replace plugs and put in K-N filter set up and see what happens, also going to check mileage at fill up see if gauge just went wacky.
Josh in CA
Here is what I have checked so far
1. No codes
2. Vacuum check with gauge. Idle goes to 20 in. Hg.. 2000rpm 20.5 in. Hg.. Rev to 5000 rpm goes to 22 in. Hg.. Stays steady at 20 in. Hg., if turn on A/C climbs to 17 in. Hg. before settling back at 20 in. Hg. Steady as a rock.
3. Checked back pressure at A.I.R. inputs to manifold per service manual, back pressure reads 0-.5 psi and oscillates like crazy, seems to low.
4. Pulled plugs checked ok, reset gap from .038 to .035, all looked good except #5 looked like it got hot. Seems every car I've ever had has this problem.
5. Waiting on test kit from madvet to check O2 sensors plus about 5-6 other things.
Going to replace plugs and put in K-N filter set up and see what happens, also going to check mileage at fill up see if gauge just went wacky.
Josh in CA
