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Originally Posted by BlazerBoyLT98
OK here we go. 1998 Blazer LT 4 Door 4X4 W 4.3. 137K miles. Recently changed plugs, wires, cap and rotor. Changed the fuel filter about 15K miles ago and I cleaned the throttle body about 5K miles ago. I run Mobil 1 5w-30 and I ran a bottle of techtron and 93 octane through to clean a little better. Basically at 60 miles an hour or higher if I floor it or give it a good amount of gas It kind of surges up to speed. The tach will hit like 3K RPMS and then surge upwards sometimes slow and sometimes fast, almost like it is bogging down as if a carb was out of sync, I know my truck is fuel injected I  have not cleaned the EGR, is that my next step? Oh and it is not throwing any codes. It was misfiring before I did the tuneup but that seemed to take care of it. Also, sometimes it starts rough like it is not getting enough gas until I give it some and then the shaking and shimmying stops and does not come back until restarted. Right before the tuneup it was running terrible, for a week after the tuneup it ran perfect, and now it is just running a little funny with the surging and with the idling rough. One more thing that has gone wrong recently is the gas gauge goes crazy sometimes and bounces all over, I have heard that could be a sign of a failing fuel pump and a bad sending unit. Thanks Everyone. |
Here is a good thing to check or a place to start..
Hard to start cold or lose of power.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.
MT