major problem with 2001 van

I have a 2001 safari van, 4.3l vortec, :banghead:
When I drive it, the engine light is on, black smoke, runs and idles rough, codes P0300, P0171, P0128, P0135.
I've changed the distributor cap, coil, wires (1 year) plugs (1 year), egr valve, several bottles of injector cleaner, which solved the problem for awhile, but problem returned.
Now, when the engine has warmed up to operating temp., the engine light blinks and the power suffers, more black smoke, idles really rough.
Could this be fuel related, temperature related or something worse???

Always start troubleshooting with the first DTC. Your first DTC of P0300 is "random misfire". Injector cleaner helping for a while, black smoke, lack of power, and rough idle all indicate a fuel delivery problem, i.e. stuck or leaking injector, leaking fuel regulator, leaking fuel line to or from the fuel regulator.

Fuel pressure is not monitored by the On Board Diagnostic (OBD) system and therefore cannot set a Diagnostic Trouble Code (DTC), or illuminate the Service Engine Soon (SES) light.

Fuel pump operation:
The fuel pump circuits are designed to energize the fuel pump through a relay continuously any time the key is in the START position. When the key is in the RUN position the fuel pump will operate provided the engine is running. If the engine stalls, or is not running for any reason, the PCM/VCM will shut off the fuel pump approximately 2 to 3 seconds after the key is turned to the RUN position.

Fuel pressure test:
Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates a leak. The most likely place is the fuel pressure regulator, or the lines under the upper intake manifold.

Here is a link to an inexpensive yet ample fuel pressure tester: http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92699

i think you have an engine going over temp. what does the guage say? i know it sounds funny but check out the cooling system first.

Thanks so much for replies.

I've taken it to our local mechanic and so far he thinks it might be a blocked catalitic converter.
Any thoughts?
Whats the best way to test cat. converters?

Thanks

Greg

A four gas analyzer will tell if it's doing what it's supposed to. If it passes, it's not restricted. If the converter is restricted, it is a symptom, not the cause of the problem.

whats a four gas analyzer?

Greg

Expensive piece of test equipment that measures carbon dioxide, hydrocarbons, carbon monoxide and oxygen as it exits the tail pipe. Someone that knows how to use it properly, can tell you if the converter is functioning correctly.

This is great, I'm learning alot from this forum! Thank you.

I must admit my mechanic is somewhat baffled by this. He is proposing to take the cat off and look for broken or blocked screening?
Is he going down the right path? We hate to second guess mechanics because they do have much more experience than us average joes.

Cheers

Not knowing what tests he ran, I can't say how he arrived at that conclussion. After a visual inspection, I would run a fuel pressure test. If that's within specs, go after the DTC's in the order they are retrieved.

It goes from bad to worst!!!

The mechanic couldn't find the answer to the problem. He did his best, checked everything, try to check the cat by taking off the last piece of exhaust, checked wires, o2 sensors, etc. It seemed to fix itself??? He removed the check engine light with the code reader. It hasn't come on again, and said to bring van in as soon as light comes on so he can check the codes. Drove it yesterday without any problems, although a little weak on power and the temp gauge didn't rise much above 70-80 degrees? Could be a sticky thermostat, about the only thing I haven't changed.
Got up this morning and there is a noticable ticking or knocking noise coming from the engine??!!! What now!!!! Sounds expensive!!
Any thoughts or comments?
Is it safe to drive to the mechanics?
Thanks again.

Any time there is a tick or knock from an engine, something is wearing faster than it should. You'll need to be the judge if it's safe to drive. Sounds like you need a thermostat, normal operating temperature is 195F. If the coolant temperature is only 70F to 80F, the oil is still relatively thick and the noise could be a valve lifter is unable to pressurize. Noises are difficult to diagnose even for an experienced technician standing by the vehicle. That's an advantage we don't have online. Check the oil, make sure it's full, then decide if you want to chance driving it to the technician.