My GMC 1500 Sierra

Asked by Sep 10, 2016 at 04:09 PM about the 1998 GMC Sierra 1500

Question type: Maintenance & Repair

Help !! I have a 1998 GMC Sierra 1500 I have done
everything I can possibly do by changing anything I
can possibly change and it's still misfiring and it is
running so bad is there any suggestions anybody
can get me I would so appreciate it

13 Answers

83,265

Vortec "spyder" injection system is not the best, you may finally have to replace the system, Have you tried run some SeaFoam in the fuel? See pic.

Doesn't have a Spyder

83,265

96, 97, 98, 99 That is what it is suppose to have. Has it been modified?

It's a 98

It's throttle body injected

83,265

So that would make it an 88 they were TBI. So then have you got the codes out of yet?

Yes it came up missfire

83,265

Random multiple, or did it give you a cylinder number?

I just bought a cam shafts positioning sensor I'm going to see if that works if not I don't know what to do LOL

83,265

Did you check for a bad intake manifold gasket?

No I will but would that cause misfiring? I mean I'm going to pull my hair out I've done all I can think of

83,265

Yes especially if it is leaking internally in the engine valley.

59,015

Have you done a compression test? Checked the ignition timing? Checked the ignition coil? If it is an '88 model it's OBD I and won't give misfire codes. Is the check engine or service engine soon light on? If so, what trouble code(s) do you have? Have you done a tune up? Distributor cap, distributor rotor, spark plugs, and spark plug wires? Does it run poorly all the time? Or only when hot? Only when cold? Only when damp/raining/high humidity? HTH. -Jim

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