Hello,
Looking for help please. My 95 GMC Jimmy, 2WD 4.3L, runs terrible-rough. Things that have been changed this weekend: Plugs, cap and rotor. Things changed in the last year: EGR valve, fuel spyder (including regulator and poppets), plug wires, and fuel pump and fuel filter. Ignition timing is good, distributor shaft seems tight, plug wires are good-not shorting out, checked the fuel spyder and regulator-no leaks, checked the EGR-okay. Car is driven about 8,000 miles a year, can't figure it out. The catalytic converter makes a rattling noise, but exhaust seems to come out fine, just rough. No check engine light, but the light does work when you first start the car, so I know it works. When I use a timing light, the timing mark is steady, and timed correctly, so I'm assuming the distributor and timing chain are okay. Any ideas? Thanks

 

what brand for plugs, wires cap and rotor?

 

Hit the cat with a mallet or your hand if it's not hot to see if the heat shield is rattling or if it's the honeycomb structure that broke. If it's the catalyst material then it can clog the flow of exhaust causing excessive back pressure and thus poor performance. But with that a cat deficiency would throw a CEL so I would start with a fuel pressure test. You could also clean the MAF, doesn't hurt. GL!

 

AC plugs, and BWD wires, cap, and rotor.

 

What would a car with plugged Cat run like? I assume lack of power but not chugging-missing. I've only seen 1 car with a plugged cat, it ran much smoother than mine, but no power like mine. I would think that my cat is just a burnt out empty shell by now, after 135k miles and 17 years of use.

 

It could be lopy with poor power, low fuel economy. Lol that's nothing, that's when most engines are hitting there prime. But like I said cat deficiency would set a code and I would start with a fuel pressure test.

 

What's your fuel pressure at? Just because the Spider assemble was replaced doesnt mean it was set right. The fuel pressure regulator is adjustable, learned the hard way on my 94, being a 95 we should have the same vin:w cpi engine.

 

Not sure, I need to buy the correct tool and check. Where and how much should I pay for a fuel pressure testor? What is the acceptable pressure range? I'm assuming I'll check the pressue at the back of the manifold, but that's before the regulator. not sure how I would check pressure after the regulator since it's all enclosed inside the intake. Thanks!

 

Fuel pressure is 52-54 PSI at idle. What should it be? 1995 4.3 W engine. I can't seem to find a clear answer on what it should be. I've seen 55-61, 60-65, and others. Mine seems on the low edge of the range. Could this be the problem? Maybe a dirty fuel filter lowering the pressure just enough to make it run bad?

 

Does the fuel pressure rise when you snap the throttle? 52-54 is low but should run fine. Low pressure wont be a dirty injector. Did you see how quickly the pressure leaked down?