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Old 11-30-2011, 11:01 AM   #1
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Default Cranking different/muffled backfire

Guys, my 2003 SE (240K miles) wouldn't start yesterday. Didn't have too much time for troubleshooting, but its getting lots of fuel, spark to the plugs, and no codes showing. Plugs have 100K on them, so I swapped out front 3 with new. No change. My compression tester was loaned out and I cant get it back quickly, so no verification of good numbers, but I don't think it would help diagnose.

It sounds exactly like old engines did when they needed a timing chain. (Cranking cadence different and muffled backfiring). So, I picked up chain and sprockets, tensioner, and gaskets for the job and will pull the cover tonight to see if the marks line up. Is there a chance the cam/crank relationship hasn't thrown a code because of too few events?

I know the chain on the 3800s are durable, but if I only had one guess it would be it.

Any ideas are appreciated.
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Old 11-30-2011, 12:25 PM   #2
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Might be as simple as bad plug wires, how old are they?.
My '87 Olds ran like a POS when I bought it, popping, banging and misfiring. Turned out the plug wires were tracking across each other, effectivly firing the wrong plugs.
If the plugs have done 100k you need to change all of them and the wires.

New plugs and wires completely cured my Olds, worth doing anyway IMO/

Roger.
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Old 11-30-2011, 02:21 PM   #3
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The wires also have 100K, but they worked fine the day before, which leads me to think its not really a degradation problem, but a more catastrophic one. It hasn't had a misfire code in 240K miles.

I'll post what I find in the morning.
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Old 11-30-2011, 02:40 PM   #4
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I'm almost put money on it not having a timing issue based on a chain. These motors are solid like SBC'*. They'd cut a hole with a loose chain before jumping a tooth.

Start off by unplugging the maf and fire up the car using some throttle etc. Keep it running with throttle for a min or so. I'm thinking the maf kicked the bucket. That'* about the only thing that should be over fueling you w/o codes etc like you mention.
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Old 12-01-2011, 11:43 AM   #5
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Billboost, you're right. Marks lined up perfectly. Chain and sprockets looked great. I'll button it back up tonite and look towards MAF and/or ECM. I should have done more troubleshooting before diving in, but my 16 year old son is becoming a pretty good wrench, and I didn't want to pass up a chance for him to see an old school timing chain and gears.

I'll let you know what I find out.

Thanks!
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Old 12-01-2011, 12:22 PM   #6
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With 100K on the plugs and wires I would start there.
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Old 12-01-2011, 01:57 PM   #7
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Reread your original post.

Do you mean the plugs are getting soaked when you say tons of fuel? If you kick the key on and off a few times and don't start it, your plugs should be wet.

But ..then you mention the off beat trying to start and backfire.. which leads me to wonder about fueling.
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Old 12-01-2011, 02:37 PM   #8
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Quote:
Originally Posted by 2kg4u View Post
With 100K on the plugs and wires I would start there.
Originals went 150K without a misfire. The OE replacements haven't had a misfire code in 95K, so I'm thinking they weren't misfiring Sunday night, they won't go to a "no start" condition Monday morning.

Bill, the plugs were very wet after 6-8 seconds of cranking. Strong fuel smell at exhaust tip was present.
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Old 12-02-2011, 09:12 AM   #9
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Sounds Mafish.. too much fuel.
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Old 12-02-2011, 11:23 AM   #10
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Ran into some family obligations, but I'll get the cover back together and go the MAF route.

Thanks, again!
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