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Super Mechanic
Super Mechanic, Master technician
Category: Chevy
Satisfied Customers: 16993
Experience:  29 yrs. exp., ASE master, cert. in G.M. electrical, a/c, susspension, brakes, electronic steering
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Chevrolet K1500 4x4: cylinder misfiring. 96 chevy 1500 5.7L.

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cylinder misfiring. 96 chevy 1500 5.7L. i've changed fuel filter, fuel injectors, egr valve, iac valve, pcv valve, plugs and plug wires. truck misses and stumbles worst in morning before engine warms up.

Hello and welcome, Super mechanic here. I will do my best to help you with your question. My goal is to help save you money and I hope you will be completely satisfied with my answer. You have the hit happy face for me to get paid for the answer. If you need any more on it just let me know. NOTE: Hitting “helped a little”, or “ I expected more”, that is negative feedback for me and we don’t get paid. Thanks

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About your vehicle.

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What is the fuel pressure?

What is the compression in the cylinders?

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Customer: replied 4 years ago.

oil pressure is low. i dont have guages to check fuel pressure or compression. seems to miss more at low throttle and run better at full throttle. could be fuel problem but only thing ive not changed is fuel pump. its been missing for a while now and ive drove it. seems fuel pump would have died by now.


 

That makes sense. There could be a vacuum leak maybe if it is just a miss at idle. Or is it more of a mid throttle stumble?
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Sorry but I just want to get a better understaning of the symptoms to get a better diagnossis, thanks
Customer: replied 4 years ago.

i've been told a vacuum leak b4. would a vacum leak cause just one cylinder to miss or all?


 

Customer: replied 4 years ago.

runs horrible b4 it warms up. even quits at idle. but once warm its just a mid throttle stumble.

A vacuum leak can make one cylinder miss if it is right by it, (like a manifold gasket leak) and if there is a big enough leak it can make multiple cylinders miss.

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On that one I would start by pinching off some vacuum hoses and see if it runs really bad if you open the EGR valve. Also, check that there is not a lot of vacuum at the oil filler, (indicating an internal vacuum leak) and spray some carb cleaner around the intake gasket to see if it has any effect on the engine RPM's.

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Customer: replied 4 years ago.

i'll give it a try

Ok, thanks
Super Mechanic, Master technician
Category: Chevy
Satisfied Customers: 16993
Experience: 29 yrs. exp., ASE master, cert. in G.M. electrical, a/c, susspension, brakes, electronic steering
Super Mechanic and 4 other Chevy Specialists are ready to help you
Hello and thank you for trusting me with your question. My name is XXXXX XXXXX I will do my best to help you with your Chevy problem.

Seems your original expert has opted out, so I will continue with you on your question. I would like you to do a fuel pressure test, as this is where we see most problems. You can get a fuel pressure gauge at most any auto parts store or Harbor Freight tools relatively inexpensively. Connect the gauge to the test port on top of the engine and cycle key ON a few times to build pressure, then let me know what the readings are.
Customer: replied 4 years ago.
ok i'll pick one up and check it. might take me a day or two to get back to u. sorry i dont get much free time.
That will be fine. I will be here when you are ready to continue. Thanks for the update!
Customer: replied 4 years ago.

ok i have a fuel pressure tester. only place i see to test on top of engine is a needle valve with threads. tester i have doesnt thread on. it says to take apart fuel lines at the tank where rubber hoses connect to metal.

The thread on connection is the test port. There is no place on this truck where there is a rubber line with a clamp that you could take apart to insert the type of fuel pressure gauge that you have. I would not suggest cutting the line. It would really be better if you can get the proper type gauge.