20 Most Recent 1998 GMC Sierra - Page 6 Questions & Answers

This year of GM Transmission doesn't have a vacuum modulator, it is all electronically controlled. And yes a shift solenoid can cause this but that should turn the check engine light on and set a fault code.

system needs bleeding

putting a toggle swicth to iac is no good, remember the iac receive info from ecu w/c calculate the air/fuel mixture base on input from ect, maf /map sensor,& tps

Have the u joints checked on the drive shaft that goes from the front diff to the transfer case one or more my be seized or loose .

yes it has to be so the transfer case doesn't blow apart

Better have brakes and wheel bearings checked. Could be dangerous.

Could be a blend door problem, or the controller.

Raise the truck with all 4 wheels off the ground, use jack stands for safety, Start the truck, engage 4hi/4lo operations , put in drive, take foot off the brake and see if the front drive shaft is turning the front diff.

be checking auto shutoff relay.. it controls ignition and fuel pump.. can you hear the pump come on 2-3 seconds before attempting to start..if not check/replace the relay..parts store can tell you where it is..

get a spark tester ,this is only a basic test .check the coil for a spark if found remove the lead from the spark plug. plug in the tester. turn the engine over to test for a spark each time. if no spark found check and clean the contacts in your distributor cap and rotor arm then refit test for a spark. at the lead to the spark plug .if found now remove your plugs one at a time .smell for fuel .if found change the plugs.