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1994 chev pu


Bentley's Avatar
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06-09-03, 03:38 PM   #1  
1994 chev pu

1994 Chevy 2500 PU, 5.7 L, auto, 180000 miles

intermittent problem-now consistent, runs like it has plugged fuel filter or timing is off.

Changed air filter, fuel filter, cap & rotor, plugs. I have used fuel injector cleaner several times...no improvement. Changing the plugs, cap & rotor improved it's "perkiness", but the roughness persists. It first presented itself entering the intererstate...choke, cough and almost die four times within 1 mile, then later it would do it climbing a mountain but still not consistently, until lately, now it runs rough most of the time. Vacuum leak? Where? It is using some oil now...catalytic converter? Help. Thanks

 
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06-09-03, 08:38 PM   #2  
You didn't mention the condition of the plug wires..Any signs of arcing or rubbing? (grayish marks anywhere along the wires)
Have you checked the fuel pressure? Also, take a look at the EGR valve. High milage GM's have been known to have the egr stick partially open (hence a vaccum leaks of sorts) and will cause a very rough running problem...

 
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06-10-03, 07:58 AM   #3  
I have visually checked the plug wires and didn't find anything wrong. Intend to check them at night with a spray bottle of water. Have you got a simple way to test the egr valve? I will check the fuel pressure next chance I get. Thanks for the ideas!

 
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06-10-03, 08:59 AM   #4  
Joe_F
If it's vacuum controlled, simply block off the line with a screw. Test the vehicle. If it solves the problem, change the valve and gasket.

MsArgent gave you some excellent ideas too.

 
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06-10-03, 10:23 PM   #5  
tiny580
my vote is fuel pump.

It is hard to check because it has to be failing to get the bad reading.

my brother had a '94 blazer do the same thing, we took it to the local shop and they were puzzled but the Gm dealer caught the fuel pump failing in the act while driving it.

 
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06-11-03, 05:26 PM   #6  
Thanks for the ideas, I'll get to work.

 
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06-11-03, 05:38 PM   #7  
Joe;

Your link to cybrrparts.com does not work. I tried going to the home page and I was told it was not available. Thought you would like to know. Thanks again.

 
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06-11-03, 07:58 PM   #8  
jetman1979
do you have a check engine light?

Do you have a check engine light? There are so many sensors it could be one of them. I had an 89 chevy 2500 that had a bad coolant temp sensor. I had the factory service manual so I quickly fixed the problem. It would run but barley and when it did it would blow black smoke and all kinds of stuff.I am sure that there is some diffrance between an 89 5.7 liter and a 94 as far as emmisions is concerned.

 
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06-11-03, 08:59 PM   #9  
Another way to check the egr valve is to reach in (preferably on a cool engine..) with your fingers, and gently pull up on the diaphram plate. The egr plunger should move freely up and down, with a slight amount of resistance.

 
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06-11-03, 09:02 PM   #10  
My vote, a cat going bad. Buy a cheap $20 vacuum gauge, read the instructions, it will tell you how to test for it. Bad cat signs are: car starts, but has less and less power (your hill), eventually it will not make it down the street.

 
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06-12-03, 09:11 AM   #11  
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Bentley:

The site works. I just tried it.

 
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06-12-03, 05:26 PM   #12  
Joe;

Still couldn't get the site to work until I thought to turn down the cookies on my computer to medium. I was able to get a diagram and intructions to replace the egr valve. Thanks.

 
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06-12-03, 05:42 PM   #13  
I don't have any check engine lights coming on.

Lugnut;

I'm guessing the "cat" you refer to is the Catalytic Converter? You had me looking through all of the diagrams for a sensor..... anything with the acronym "cat" until it dawned on me. I guess I could use a "cat" to make this engine PURRR. Thanks for the help.

 
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06-12-03, 06:35 PM   #14  
Joe_F
Cat=Catalytic Converter. Not likely to be the problem, and if it is, something causes it to go bad (a rich running condition).

 
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06-12-03, 10:58 PM   #15  
hey mr. bentley, hope you found something by now, but if you didn't, don't forget the lowly(but very important) oxygen sensor, i know for a fact on gm vehicles it will cause exactly what you are describing, it to feel like someone is almost turning the ignition off it bogs down so bad, usually you will have a stored fault code though(i think 44--lean exhaust)however many things can cause this too, like a weak/failing fuel pump, an intake leak or even tiny amounts of water in the fuel, a fuel pressure guage will confirm the pump. does the problem somewhat clear up if you put your foot to the floor, one sign of a bad sensor. has your fuel mileage dropped way off and the exhaust stink horrendously---more signs of a bad sensor,(if it hasn't been done already in 180,000 miles, consider yourself lucky, they're almost a maintenance item)what you should do is get your hands on a book, either online or at the library, a mitchell manual in particular and find out how to check for codes and what they mean before you start throwing darts(parts) at a car until you hit the bullseye, you CAN have a stored fault code without a check engine light, especially before 1996 model year.
easiest way to eliminate the egr valve is to unbolt it, cut up a "soft drink" can with scissors roughly to the shape of the bottom of the valve and place your new block-off plate between the valve and the manifold, if the problem is fixed, just make sure you take it out before you go to inspection(if you have a dyno program)your NOx will be skyhigh, it's also not a good idea to drive for long like that, other things might happen
a cat going bad... maybe, maybe not, one easy test is with a rubber mallet(or sneaker or boot) and hit it, any rattling is bad, but not the rattling of a broken heat shield on the outside, the noise has to come from inside to make it be "bad" however it can also be quiet and bad too so don't rely on that too heavily, a vacuum guage test done correctly is a much better test but requires some knowledge, again, i like the mitchell manuals when you can't afford a $100 service manual
let us know what you find

 
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06-13-03, 08:42 AM   #16  
Just checked the EGR valve now that I know which part it is. There is no vacuum getting to it. The vacuum first runs through a device located above and in the center of the valve cover on the right side of the engine. I reached in under the top of the valve with my finger to try and move the diaphram..... coudn't get anything to move. Have we found the problem?

 
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06-13-03, 08:55 AM   #17  
Joe_F
Might be. Take it off and have a look. Is it stuffed with carbon and does the diaphragm feel "crunchy" when you try to push up on it?

Sounds like it's wiped out to me. GM vehicles of this vintage are notorious for stuffing EGR valves.

 
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06-13-03, 09:34 AM   #18  
Joe:

Thanks again. Just got off the Auto zone web site where they highly recomend cleaning the carbon out of the egr valve port when replacing it, but they didn't say what to use. If memory serves, I think I remember someone recomending WD 40? What do you use?

 
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06-13-03, 10:58 AM   #19  
Bentley,

You should not be getting vacuum to the EGR valve with it sitting there idling. The Egr valve doesnt come into operation until around 45mph. You should check the vacuum BEFORE the solenoid (the thing above the valve cover) If you are getting vacuum there, take the line loose from the EGR valve side of the solenoid and pull a vacuum and watch the diaprham of the EGR valve. This is not a true test that it is good, but it will at least let you know that it operates. If you have a vacuum gage, pull the vacuum and watch the gage to see if it moves..... You should watch it for 20 minutes or so to see if you have leak down. If you have leak down then the diaphram has been compromised and the EGR valve will definately have to be replaced. As for what to use to clean the port, any good cleaner will work. I use throttle body cleaner as it works best. Just be sure to let it dry thoroughly before cranking as you can have a flash fire on your hands.
Hope this helps,
Billy

 
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06-13-03, 01:22 PM   #20  
Thanks for the clarity. I'll get to work.

 
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