Question about 1998 GMC Sierra
Warm engine idle loping when in park, in gear
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Posted on Jan 02, 2017
SOURCE: rough idle and lopes
Those 4.3L's have a Central Port Fuel Injection system with one injector in the middle of the intake under the plenum, they are good for either the fuel pressure regulator or the plastic lines (that are inside the intake that feed the injector) leaking inside and flooding the intake with fuel. The best way to tell is to take the plenum off and thurn the key to prime the fuel pump and watch for leaks.
Posted on Nov 18, 2008
30-40 psi of oil pressure is fine for many vehicles including your GMC. I am assuming that the truck has more than 100,000 miles on it and still has the original engine in it. By rule of thumb you only need 10 psi per 1000 rpms in a typical street driven engine to give adequate oil pressure to keep the bearings from oil starvation. The oil pressure is typically higher when initial start up occurs because it is more viscous due to the temperature of the oil as the engines oil warms up the visconsity thins out and the oil flows more smoothly. The drop in oil pressure is a normal occurance. Above 45 is more than required for a daily driven street engine. I believe that the specs on that engine only list 30- 45 psi.
Posted on Dec 07, 2008
have you replaced your intake gaskets? this is a problem on these trucks with high milage. to see if your intake is leaking spray it down with Brake cleaner and if it is leakin you will hear a drop in Rpm's
hope this helps
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Posted on May 08, 2009
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