1992.Silverado K3500 7.4 Liter,Manual Trans

[stevep]

Pulsing Idle... Sometimes accompanied by "Service engine soon" light. it s about 100 RPM pulse. Then it will smooth out and then it will start again. O2 Sensor or some other Sensor , or Fuel Filter...Its been a good long while since I ve changed that. Runs fine other than the Idle Bug..

[carriedi]

you should have the engine scanned for memory codes. Hopefully the computer will save the check engine light code and you can see what the computer thinks is going on with your engine. wrong fuel pressure, vacuum leak, things that the computer is trying to compensate for.

[stevep]

Thanks for the answer but I ve tried to ask the local O reilly for a scan and then they Launch into " Well Thats a pre omb or something model , so our scanner wont give you a correct code, So far I ve replaced the thermostat Sensor, and at the suggestion of the Counter guy.... a mass air something thing on the top of the manifold.... LOL Im making them money , but I dont think they know what they are doing LMAO..I know I dont ! So////anymore IDeas? You guys have never let me down yet .... Its gotta be something simple...

[carriedi]

most places that scan for free are going to have OBD2 scanners because it is a universal type scanner from 1996 and on. (some models of cars used OBD2 starting in 1994).

a 1992 will use the old software and hardware that has to have the GM adapter. Most auto repair shops will have the older stuff to scan your vehicle. They will probably charge you for the scan but their information should be better than an auto parts employee's guess. Call around your area and see what price you can get it scanned for. It may be cheaper than buying parts and see if it changes anything.

there are so many things that can cause the symptom you have. EGR,vacuum leak, ecm and/or prom, fuel pressure (pump or regulator) and on and on. Someone has to check these things to see what area to concentrate on.