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I was googling a problem with my truck and found your

Hi, i was googling a...
Hi, i was googling a problem with my truck and found your answers on a thread, you were pretty thorough, figured I'd ask you a question about my truck. I have a 95 Chevy K1500 with a 5.7L. It seriously lacks power at speeds greater 30mph. On the highway, when you punch the gas pedal the tranny will shift and the engine will rev up to 3K rpms and all, but there's no output. It will actually loose speed when you punch it. I've noticed if you keep the RPM's below 2500, it does ok. Above that and the engine looses power, and sometimes surges. There are no trouble codes, which is frustrating, I wish there was. It would give me a place to start. I've done everything I can think of. Checked the timing, tried a couple degrees advanced, a couple degrees retarded, no change. I've changed the fuel filter and checked the fuel pressure, it holds steady at about 11-12 psi throughout driving range. I've checked the spark plugs, they're fine. Checked the plugs wires, and replaced them. Changed the air filter. Did a 50% fluid change on the transmission and replaced it's filter. I've checked for vacuum leaks many times, both by listening and using starter fluid to see if engine surges. I've checked the TPS by back-probing with a multi-meter, it seemed to work perfectly fine, but i replaced it anyways. I've completely taken apart the TBI and replaced the fuel pressure regulator and all of it's gaskets and the screens for the injectors. It seems to run a little better since i did that, as in better power at slower speeds, but still has the same problem at higher speeds. A friend of mine said to check the catalytic converter, but i don't really know how to check it. I don't know, I'm out of ideas. Do you have any?
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Answered in 1 hour by:
3/21/2018
Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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I agree with your friend, this smacks of a catalytic converter that is plugged up.

The test is with an exhaust back pressure gauge. You can borrow this tool at some parts stores, like Autozone and Advance. Remove the oxygen sensor and install the gauge, then go drive it while watching the gauge (tape it to the windshield so you can see it). Allowable back pressure is 1psi, if you mash the throttle and it has no power, and the gauge goes off the scale, you need to replace the catalytic converter.

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Customer reply replied 3 months ago
Makes sense. I replaced the cat a few yrs back, but by truck burns oil, so it may very well be plugged up. I will do that asap and get back to you. Thank you.

Please take a moment to rate my answers by clicking on the stars at the top of the page, that's how I get compensated. If you need more help, just let me know, I am happy to follow up

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Customer reply replied 3 months ago
Tried to rent one of those exhaust back pressure gauges, NOBODY had them. Not Auto Zone not O'Reilly, not car quest. And I don't have one of those thermometers to check the temp before and after the cat.
So instead I just pulled the O2 sensor out , left the hole open, and went for a drive!
It was loud, but the truck ran a LOT better!
Tells me the cat is clogged up, and exhaust can’t breath right.

I think you're probably right.

:-)

Please take a moment to rate my answers using the stars at the top of the page, that's how I get compensated. Let me know if you need anything else, I am happy to follow up.

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Customer reply replied 3 months ago
I might even replace my entire exhaust system. I hear flowmaster is good. Is there a specific brand/part number you would recommend? Must be California legal.

Flowmaster is good stuff. Magnaflow is also good stuff, I prefer Magnaflow products when we're talking about performance exhaust.

California law says you have to buy a converter from the dealer, you can't purchase aftermarket converters (this is my understanding of CA law, anyway. I don't live or work there). It's the only state in the country with this mandate, so I don't know the legality of purchasing a complete front to rear exhaust kit and installing it. Seems to me that you will have trouble with this come emissions inspection time, if they look under there and don't see an OEM converter.

Otherwise, I agree with you, it's a great option and you'll really like the way it looks and sounds.

Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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Customer reply replied 3 months ago
Update: Replaced the cat yesterday. MUCH better. I can go past 50 on the highway now. Lol. This whole time. Months of throwing money into it and a plugged up cat was all it was. Wow. Thank you. I gave you 5 stars.

Thank you! Nice job!

:-)

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