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Author
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Topic: 92 LX stumbling/backfiring!
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JohnB
Tech Moderator
Member # 969
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posted
 
 
OK folks, here goes- picked up a 92 LX 5.0/auto and it runs good at high rpm (2,000+) but at idle/acceleration...it stumbles and hesistates. At idle, it will backfire (very small and noticable) and barely hold an idle. Car is completely stock, no mods. Any ideas? My first change will be the MAS, the computer, then the distributor...any other thoughts? thanks!
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Gear Head
JARED
Member # 779
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posted
My buddy brians 90gt is doing the exact same thing but it only does it when hes letting out the clutch and his is in the intake. Were changing his plugs first. You might wanna try that before u spend some bucks on a whole new comp.
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Posts: 5685 | From: EASTBAY | Registered: Jan 2002
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JohnB
Tech Moderator
Member # 969
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posted
The backfire is through the exhaust. Unless it idles for an extended amount of time(more than 45 sec) it just sounds like a pop through the pipes. I plan to give it a full tune-up, clean the throttle body and idle air bypass valve, and go from there. As for the parts swap-out, I've got the items readily available, so it makes the troubleshooting a lil easier...
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Stimson
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Member # 51
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posted
Through the exhaust means rich, through the intake means lean. Check your O2 sensors. Instead of spending all that time randomly swapping parts, why not pull the codes so you have a much narrower list of parts that could be wrong.
Posts: 2373 | Registered: Jun 2000
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JohnB
Tech Moderator
Member # 969
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posted
I tried to pull the codes, via the key on/key off method...it didn't generate anything. I don't have a handheld, so that's out the window. Did a "poor-mans" spark check, turns out 1 and 3 are dead(engine ran the same w/o them), so the next thing is new plugs/wires. Hopefully that checks good afterwards. The firing order was correct, that was my first thought. Checked the EGR, all is working fine.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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JohnB
Tech Moderator
Member # 969
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posted
Ok, did a full tune-up (plugs,wires,cap,rotor)...and it runs like a champ! All the parts were the originals...all the way down to the plugs. The gap was somewhere around .080, as the electrodes were fried. Thanks to all of you for your advice-
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Gear Head
JARED
Member # 779
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posted
My buddy brian and i hooked up his car to a diagnostic analyzer in auto at school and it said that his 3 and 4 cyl were either not lighting properly or backfiring. So as we were going to change the plugs we noticed that his 3 and 4 plug wires were switched around. What a dumba22.
I'm just glad that we got him off 6 cyl and back to 8.
Posts: 5685 | From: EASTBAY | Registered: Jan 2002
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