Got a 1999 Silverado 4x4 with 4.3 vortec. Runs very rough at stop light, check engine light stays on. New plugs, wires, dist cap, rotor, ignition module, MAP, and Warm exhaust air sensor. Air filter is new an throttle body is clean. Fuel pump is good as well. Engine has 160k + miles and has original spider injector and pressure regulator. I am feeling pretty confident that I should replace the spider injector. Saw older post put want to make sure not missing anything else. Thanks
Scan it, and get back to me. EGR valve stuck open, fuel pressure regulator ruptured, reversed plug wires, bad plug, no compression...
Had is scanned not long ago, codes indicated MAP(replaced), warm air sensor on exhaust bank 2 (replaced), new a/c delco plugs, wire, dist cap, ignition module, cap, and rotor (I was ill so had to let dealer do it), I have verified that no wires are crossed. Still need to check EGR. runs extremely good above 30 mph. Loads up at stop light, exhaust pipe black and sooty. Pulls like a mule when in 4x. Also takes a while to crank. Throttle body was extremely dirty when I cleaned it.
I appreciate the help. I am an old timer that used a feeler gauge, dwell tach, and vacume gauge to turn low 12's in quarter. (8 track were still new for tunes)
As others have said, let us know what codes still remain after the parts that have been recently replaced.
Pull the distributor. It is probably very worn. Free to check. Happens a lot with the plastic dist shafts.
Ck codes ck dist ck wirimg to map ck wiring under fuse box under hood
I just had to replace the distributor on my '96 Chevy C1500 with a 350. The cam position sensor, which is on the distributor, was bad. I had just recently replaced the upper and lower intake manifold gaskets, and the spider too.
Would sometimes shift hard, and had a stumble when at a constant speed while in third gear. It pulled strong while accelerating though.
Streetwiseguy wrote: Scan it, and get back to me. EGR valve stuck open,
On a 4.3L, I would bet good money on EGR. They get crusty and stick open. They're right on the front of the engine and pretty easy to whack with a stick. Do that and see if you get any changes.
If you don't, another thought is something downstream; O2, catalyst, etc.
Long cranking could be crank position sensor, but typically once it fires its good. It has to spend a few more revs cranking to determine the cam position which is half the speed. Once it gets it, they usually run pretty well. Worth checking, but I doubt that's the issue on that GM.
Oh... IAC can get crusty too. It can't do its job regulating idle air.
Update: IAC and EGR cleaned, they were not too bad. Have not got a chance to check the codes. Interesting find though. Checked my oil, 2 quarts to much. Drained and put in fresh oil. Old oil very thin and smelled of gas. Trans fluid and coolant level unchanged. I think the fuel regulator and spider are done for.
Thanks for the help and ideas. I pulled the upper intake plenum. Manifold port 3, 5, & 6 washed completely clean. Put in the new mpi now runs better than new! Thanks again for all the ideas, they all helped getting it running like new again. Latter
Glad to hear it.
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