Mechanics

GMC SUBURBAN ENGINE PROBLEM

1996 GMC Suburban • V8 4WD Automatic • 185,500 miles

Have a 1996 gmc 1500 suburban 5.7 350 engine. When the truck hits 65mph there is a slight backfire and the engine statrs to buck a little. Have given truck full tune-up. When it rains problem is even worse until engine warms up. Any solutions? Even my mechanic is stumped at this point. Also have two codes 420 and 300. Cant get rid of
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Cookies95
June 15, 2011.




My advice would be to have your mechanic use a water solution in a spray bottle and start spraying ignition components (coil, wires, cap, rotor, )
And see if engine reacts, this is usaully my direction of attack when a customer complains of running bad when wet.
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PROTECH1980
Jun 15, 2011.
Thats not where the problem lies. GMC almost always puts it distributor right up against the fire wall in its trucks and the rain gets under the hood and drips on the cap and wires. Had same problem with 1989 gmc jimmy and everything is brand new-plugs, wires, cap, rotor. Have been told that the distributor itself needs to be changed moisture is getting inside and causing problem.

Tiny
Cookies95
Jun 15, 2011.
Unless your missing your rubber weather strip that runs along the top of the fire wall there should be no water getting on the distributer, just because you have new parts doesnt mean there ok, bad new parts happen, as for moisture getting in the distributer, that one has a small vent on the bottom side, alot of times that doesnt get cleaned out during cap and rotor replacement resulting in premature failure, (wet cap), another cause is the little ears on the distributer that the cap bolts/screws through, they crack, not allowing for proper seal of cap also resulting in wet cap and rotors.

PROTECH1980
Jun 15, 2011.

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