I have an 88 Gulf Stream Sunsport that I recently bought. It has been sitting for 2 years and it runs good except at about 50 to 55mph it back fires thru the exhaust. E have changed plugs and wires and rebuilt carb. Does anyone know if it has an inline fuel filter? Also the distributor and coil looks new inside?

There should be a large in line filter along frame rail just in front of right rear wheels.Carb getting rebuilt should have taken care of filter in the inlet port there. Backfiring is more likely to be electrical. Check to make sure the plug wires go to the correct one.Check the EGR valve and vacuum control lines.Does the back firing happen during acceleration or deceleration?

A filter isn't going to make it backfire through the exhaust.Did it do that before the new plugs? Does it do it more under a load? Is there a stumble feeling? (EGR)If a plug gets cracked during installation it can act like that. You could also have one or more valves sticking because it sat so long. Running some good fresh fuel with a can or two of Seafoam through it may take care of that if it's the case.

It does the back fire during acceleration of 50 to 55. It did it before and after changing new plugs and wires

Crossed plug wire.Verify firing order and wiring.

Thank you for you help! Will try these things and get back with you both. Hopefully I can get this fixed by wed nite. Suppose to leave on a short 2 hour trip on thurs morning?

454 Back fire thru exhaust | Good Sam Community

12 Replies

ScottG
Nomad
Jul 08, 2014
A filter isn't going to make it backfire through the exhaust.
Did it do that before the new plugs? Does it do it more under a load? Is there a stumble feeling? (EGR)
If a plug gets cracked during installation it can act like that.
You could also have one or more valves sticking because it sat so long. Running some good fresh fuel with a can or two of Seafoam through it may take care of that if it's the case.
enblethen
Nomad
Jul 08, 2014
There should be a large in line filter along frame rail just in front of right rear wheels.
Carb getting rebuilt should have taken care of filter in the inlet port there.
Backfiring is more likely to be electrical. Check to make sure the plug wires go to the correct one.
Check the EGR valve and vacuum control lines.
Does the back firing happen during acceleration or deceleration?

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454 Back fire thru exhaust

12 Replies

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