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Loss of power?

Tiny
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  • MEMBER
  • 1997 GMC SUBURBAN
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 180,000 MILES
The truck listed above is a K1500 with a 5.7 vortec. I changed pump, intake gaskets. Spider injection, plugs wires, distributor, still no power.
Wednesday, December 28th, 2022 AT 2:33 PM

24 Replies

Tiny
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  • MECHANIC
  • 108,269 POSTS
Hi,

I assume that is the fuel pump you replaced. Was there any change after you did this work? Does the check engine light stay on when the engine is running? If so, have you scanned the computer for diagnostic trouble codes?

On the other hand, anytime I hear there is power loss, the first thing that I think is plugged catalytic converter. Are there any strange sounds from the exhaust? Are there any strange odors from the exhaust?

Take a look at this link. It discusses the symptoms of a plugged catalytic converter. See if anything mirrors what you experience.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

Let me know. Also, let me know if the vehicle is drivable, if there is any backfiring, or anything you can think of that may help me.

Take care,

Joe
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Wednesday, December 28th, 2022 AT 10:38 PM
Tiny
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Hi Joe, no cats on burb, new fuel pump, filter, spider assembly, I made sure all injectors went to numbered pistons, new tps, yes codes are for the missing 02 sensors. I was wondering if their is a vacuum to the fpr on the spider assembly. ?
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Thursday, December 29th, 2022 AT 11:05 AM
Tiny
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Hi Joe, btw no change at all after replacing all those parts, also compression. At 150 across all cylinders.
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Thursday, December 29th, 2022 AT 12:35 PM
Tiny
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Hi,

The compression is perfect. There is a vacuum supply to the regulator. See pic below.

By chance, do you have a live data scan tool? If you do, could you check the short-term fuel trims when the engine is at operating temperature?

Let me know.

Joe
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Thursday, December 29th, 2022 AT 8:53 PM
Tiny
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Hello, yes I have a live scan tool. Ok. So the fpr has an open vacuum port with no vacuum line to it. Is it suppose to have a vacuum line attached to it?
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Thursday, December 29th, 2022 AT 9:35 PM
Tiny
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Hi,

According to the manual, the engine vacuum should be there. Take a look at the attachment below. It is the description of how it works.

Let me know your thoughts.

Joe
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Thursday, December 29th, 2022 AT 9:54 PM
Tiny
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Hi Joe, my thoughts are, their is no vacuum. Line inside the valley to hook up to !.
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Friday, December 30th, 2022 AT 12:04 PM
Tiny
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Hi back again. I found this part # A.C. 17113556, however it's application. Is for 99 to 05. I read the whole plenum itself acts as a vacuum for that 97. K1500. But ordered the line anyway I'm willing to give it a try.
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Friday, December 30th, 2022 AT 3:22 PM
Tiny
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Hi,

Anything is worth trying. LOL You know, I went back to the manual and found once again what I sent you pics of. When you had things apart originally, do you recall seeing that regulator? From memory only, I swear that the regulator was part of the fuel meter body assembly.

Let me know. Also, if I don't hear from you, I wish you and your family a great new year!

Joe
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Friday, December 30th, 2022 AT 11:29 PM
Tiny
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Hi Joe, yes, the fpr is located on left side, passenger side of the meter body it has a down facing air port for a vacuum line, I did order that vacuum line, and yes anything is worth trying to get it fixed. I hope y'all have a blessed New Year also Sir.
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Sunday, January 1st, 2023 AT 11:43 PM
Tiny
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Hi,

Thanks for the update. Let me know how things turn out. I'm interested in knowing.

Take care,

Joe
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Monday, January 2nd, 2023 AT 3:44 PM
Tiny
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Hi Joe, good morning, part came in yesterday, been bit under weather here, trying to jump on it today maybe. But will keep you posted Sir thank you.
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Wednesday, January 4th, 2023 AT 7:49 AM
Tiny
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Hi Joe, I got the new vacuum line in place, no change at all Sir. No power.
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Wednesday, January 4th, 2023 AT 5:37 PM
Tiny
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I'm going to ask the site owner for his input. You have good fuel pressure, no cats, and the compression is excellent.

Please correct me if I'm wrong, but there are no codes and the engine does not misfire, correct?

Let me know.

Joe

Note: You may get a response from Ken. I'm interested in hearing what he has to say.
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Wednesday, January 4th, 2023 AT 8:38 PM
Tiny
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Hi Joe, so yes compression 150#s across board, New fuel pump, , filter, tps, spider assembly and aed vacuum line to the fpr, plus , New distributor, when I cranked it after completion today, it cranked so strong like a brand new truck. Put it in drive, no power, rev it up sounds great, but gotta baby gas to get up to 30mph, no cats, only code were tps, already changed and verified operation thru live data, getting stumped here. Ed.
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Wednesday, January 4th, 2023 AT 9:47 PM
Tiny
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Typo , "aed", before word vacuum. On previous message.
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Wednesday, January 4th, 2023 AT 9:49 PM
Tiny
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Yes, fuel pressure stays around 55 to 60, it does hold. And fluctuate a bit on demand, not much, couple #s up or down, I have a 90 psi rated pump on it, this is second pump on it brand new, nothing wrong with first one I swapped, just to rule it out. Same pressures. Ed.
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Wednesday, January 4th, 2023 AT 9:53 PM
Tiny
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There isn't a lot left. Do me a favor. Disconnect the MAF and let me know what happens. Also, if you have a live data scan tool, check the engine coolant temperature signal to see if it seems accurate.

Since the engine starts strong and when it gear it loses power, with our luck, you have a wheel hung up. LOL

Let me know.

Joe
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Thursday, January 5th, 2023 AT 1:53 PM
Tiny
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Joe, that engine cranked up like new last night, only to burp and fall on its face, I can run quicker probably. And no, no tires hung up. Funny but no. Wish it was. Ed.
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Thursday, January 5th, 2023 AT 2:10 PM
Tiny
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I'll get on it in a bit, I did clean it up, the temperature gauge on the coolant rises proper when idling, btw it idles and revs good.
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Thursday, January 5th, 2023 AT 2:13 PM

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