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93 caddy backfiring


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kentr
Novice

Feb 10, 2010, 2:44 PM

Post #1 of 11 (1503 views)
93 caddy backfiring Sign In

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?


re-tired
Veteran / Moderator
re-tired profile image

Feb 10, 2010, 5:25 PM

Post #2 of 11 (1500 views)
Re: 93 caddy backfiring Sign In

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


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 11, 2010, 6:15 AM

Post #3 of 11 (1494 views)
Re: 93 caddy backfiring Sign In

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....





kentr
Novice

Feb 12, 2010, 11:20 AM

Post #4 of 11 (1481 views)
Re: 93 caddy backfiring Sign In

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?


re-tired
Veteran / Moderator
re-tired profile image

Feb 12, 2010, 11:19 PM

Post #5 of 11 (1474 views)
Re: 93 caddy backfiring Sign In

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


kentr
Novice

Feb 19, 2010, 3:34 PM

Post #6 of 11 (1452 views)
Re: 93 caddy backfiring Sign In

Thank you sir,
The ground cable fixed the problem, Now go Fish, you deserve it.
Thanks againSmile


Loren Champlain Sr
Veteran / Moderator
Loren Champlain Sr profile image

Feb 19, 2010, 6:51 PM

Post #7 of 11 (1448 views)
Re: 93 caddy backfiring Sign In

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!!!!SmileSmileSmile
Loren
SW Washington


re-tired
Veteran / Moderator
re-tired profile image

Feb 19, 2010, 8:35 PM

Post #8 of 11 (1443 views)
Re: 93 caddy backfiring Sign In

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 Tongue


LIFE'S SHORT GO FISH


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 19, 2010, 9:23 PM

Post #9 of 11 (1441 views)
Re: 93 caddy backfiring Sign In

Excellent R-T!

Loren - did they show you where we hide the company stars?





Gotta look for them..........



Tom



Loren Champlain Sr
Veteran / Moderator
Loren Champlain Sr profile image

Feb 20, 2010, 12:31 PM

Post #10 of 11 (1431 views)
Re: 93 caddy backfiring Sign In

LOL; I found a couple under the stacks of uncashed CarJunky payroll checks! Can't get the stars to work, either. Wink
Loren
SW Washington


re-tired
Veteran / Moderator
re-tired profile image

Feb 20, 2010, 1:39 PM

Post #11 of 11 (1424 views)
Re: 93 caddy backfiring Sign In

That's ok Loren . It's the same as with the checks that don't work.......It's the thought that counts. Wink


LIFE'S SHORT GO FISH






 
 
 






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