blow thru? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 02-17-2008, 07:48 PM   #1
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Default blow thru?

My sis has a 90 SE with the 3800 and it wouldn't start yesterday. Replaced the wires cuz the old ones were arking. Now, and yes firing order was checked, getting a backfire of sorts thru the throttlebody while trying to start it. It won't start but about the 3rd crank on the starter is when the blow thru happens. Any ideas gearheads?
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Old 02-17-2008, 08:12 PM   #2
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Double check the wire routing from the coils to the plugs. Then, pull the hose off the fuel pressure regulator - look and smell for fresh gasoline.

If the motor is a VIN "C", with the motorola coil pack, the wires run differently than your newer 98. On the vin C the routing is:

....................2........4........6 (rear bank cylinders)


.....3
.....................6
.....5
.....................2 (coils)
.....1
.....................4


.................1.........3.........5 (front bank cylinders)
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Old 02-18-2008, 12:16 AM   #3
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I now the firing order is different. I found a post with the firing order in here . I'll check the hose tommorow. thnx
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Old 02-18-2008, 01:02 AM   #4
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Backfire often implies a timing problem, but for the no-start condition, the first thing to determine is whether or not you have spark and fuel available.
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Old 02-18-2008, 09:58 AM   #5
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Also if you bought cheapo ~$20 wires, crossing them at multiple places can make the spark jump... so make sure you use the wire separators as much as you can...
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Old 02-19-2008, 12:10 AM   #6
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Got it to start after tinkering with it, and I gotta say, i'm suprised it runs. Backfires every 20 seconds or so and sounds like adiesel chugging up a steep incline. Timing belt is toast. Another Bonnie goes dowm the drain. But it wasn't White!
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Old 02-19-2008, 01:35 AM   #7
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Quote:
Originally Posted by Jason1351
Got it to start after tinkering with it, and I gotta say, i'm suprised it runs. Backfires every 20 seconds or so and sounds like adiesel chugging up a steep incline. Timing belt is toast. Another Bonnie goes dowm the drain. But it wasn't White!
It would be the first Bonneville to fail due to a bad timing belt - doesn't have one - has a chain. Jumped time is a more common problem with the older (87?) engines that had the nylon tipped gears, but is a pretty rare problem in later years.
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Old 02-19-2008, 10:28 AM   #8
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Sorry, i'm used to dealing with older engines that have chains. Pretty much, anytime I talk about a newer than 87, I say belt cuz so many newer engines have em.
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Old 02-19-2008, 11:41 AM   #9
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I had an 86 Olds 88 that barely ran due to being off time. I used it for about 5 months to get back and forth to school though just because I had absolutely nothing else.

If you wanted to keep the car, it would be fairly easy to get a "new" block from a junkyard and swap it in. I wouldn't think it would be worth it to try to fix the current motor as it probably has mashed valves now from the timing being off.
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Old 02-19-2008, 10:47 PM   #10
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Non-interference motor, so no bent valves. All he needs is a $50 timing set and a few hours of time [ heh pun intended].
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