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kentr
Novice
Feb 10, 2010, 2:44 PM
Post #1 of 11
(1506 views)
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93 caddy backfiring
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This is for a friend that owns a small shop and has been working on cars since '74.
The car came into the shop with a broken rocker arm, fixed that. Burnt plug wire, fixed that. Expected car to run but still had back fire issues. Scanner cannot communicate with ECM while running, only with key on engine off. Compression good. Scoped ignition system, looks good. Scoped injectors, looks good. Ohm'd injectors, looks good. Checked EGR, no problems. Changed ECM, and Distributor.
This is an intermittent problem, sometimes runs perfect then will start to backfire again.
Any Ideas where else to look?
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re-tired
Veteran
/ Moderator
Feb 10, 2010, 5:25 PM
Post #2 of 11
(1503 views)
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Re: 93 caddy backfiring
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Is it back firing (out the exhaust) or popping back (out the intake) ? Which rocker broke , I or E ? Next time you can get it to do its thing ,try dropping one cyl at a time till it goes away ,then you have narrowed down the search.
LIFE'S SHORT GO FISH
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 11, 2010, 6:15 AM
Post #3 of 11
(1497 views)
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Re: 93 caddy backfiring
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Add a guess: Valve spring may be at fault! They can show good compression but not fast enough or strong enough when running. They can split and stay in place. Scary as if that's it and valve falls down it's game over for that engine!
T
Pic is not of you engine but example of what can happen....
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kentr
Novice
Feb 12, 2010, 11:20 AM
Post #4 of 11
(1484 views)
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Re: 93 caddy backfiring
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back firing out the exhaust. Tried to find which cylinder it was by taking off the plug wire one at a time, but could not locate suspected cylinder. I don't think that it is an individual cylinder.
Just yesterday started car and it ran ruff at idle then for a moment would smooth out, but for only a moment. hit the accelerator runs ruff (labored) then starts to backfire out the exhaust.
I think that it has to be in the ignition system somewhere. Ideas?
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re-tired
Veteran
/ Moderator
Feb 12, 2010, 11:19 PM
Post #5 of 11
(1477 views)
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Re: 93 caddy backfiring
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Caddywacks have a problem with poor eng grounding that can cause backfiring ,poor performance under a load. Follow your ground cable down to front of eng . It should be attached to block with a stud and nut.,.Unbolt it and clean everything real good , reinstall be sure stud is tight.Be sure to clean batt terminals also.
LIFE'S SHORT GO FISH
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kentr
Novice
Feb 19, 2010, 3:34 PM
Post #6 of 11
(1455 views)
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Re: 93 caddy backfiring
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Thank you sir,
The ground cable fixed the problem, Now go Fish, you deserve it.
Thanks again
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Loren Champlain Sr
Veteran
/ Moderator
Feb 19, 2010, 6:51 PM
Post #7 of 11
(1451 views)
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Re: 93 caddy backfiring
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re-tired; You da' man! I'd have never gone there. If I could figure out how, I'd give you at least two gold stars!!!!
Loren
SW Washington
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re-tired
Veteran
/ Moderator
Feb 19, 2010, 8:35 PM
Post #8 of 11
(1446 views)
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Re: 93 caddy backfiring
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Aw shucks......Now your ** in bare assin me ** When you spend half a day finding a fix like that, it tends to stick with you for a while 
LIFE'S SHORT GO FISH
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 19, 2010, 9:23 PM
Post #9 of 11
(1444 views)
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Re: 93 caddy backfiring
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Excellent R-T!
Loren - did they show you where we hide the company stars?
Gotta look for them..........
Tom
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Loren Champlain Sr
Veteran
/ Moderator
Feb 20, 2010, 12:31 PM
Post #10 of 11
(1434 views)
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Re: 93 caddy backfiring
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LOL; I found a couple under the stacks of uncashed CarJunky payroll checks! Can't get the stars to work, either. 
Loren
SW Washington
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re-tired
Veteran
/ Moderator
Feb 20, 2010, 1:39 PM
Post #11 of 11
(1427 views)
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Re: 93 caddy backfiring
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That's ok Loren . It's the same as with the checks that don't work.......It's the thought that counts.
LIFE'S SHORT GO FISH
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