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04-06-2021, 09:03 AM | #1 |
Registered User
Join Date: May 2013
Location: Mississippi
Posts: 501
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Loss of power on acceleration when warm, backfires a lot.
I have an 87 Suburban with a 6.0 LQ4.
For a while now, when the motor is warmed up, when I go to accelerate sometimes it will bog down and not want to move. When this happens it backfires like crazy, and if I keep the accelerator pedal pressed once the RPMs finally get up the truck will accelerate and get up to speed. When I did the swap 5 years and 16,000 miles ago I replaced the spark plugs, plug wires, fuel filter, ignition coils, and MAF sensor. I did not replace the fuel injectors. I have a fuel gauge mounted to my fuel rail that shows a constant 58 psi at idle. I do not have any check engine lights or any stored codes. Any Ideas where to start?
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1987 R20 Suburban LQ4/4L80e swap: http://67-72chevytrucks.com/vboard/s...d.php?t=693824 |
04-06-2021, 10:46 PM | #2 |
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Join Date: Dec 2009
Location: Independence Mo
Posts: 4,119
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Re: Loss of power on acceleration when warm, backfires a lot.
Sounds a lot like a fuel pressure problem. I would hook up the gauge and check pressure while under load if possible. Maybe change the fuel filter if it hasn't been changed in a while.
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My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html |
04-09-2021, 06:02 PM | #3 |
Old and crusty
Join Date: Jan 2009
Location: Surprise, AZ
Posts: 462
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Re: Loss of power on acceleration when warm, backfires a lot.
Not sure why you aren't getting any codes. Running that poorly should trigger some response from the computer.
My truck with 5.3Vortec motor was running like crap for a while, including some back firing and very rough idle and poor throttle. The only codes I was getting was lean condition on the left bank. I tried a few basic tune things to no avail. One day I decided to take off the bracket that holds the coils on the left side just to clean things up and inspect the coils. I had already installed new plugs and wires. One of the coils was cracked on the bottom side and could not be seen unless it was removed. I had some spares so I changed out the coil and it runs perfectly again.
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65 Chevy long wide daily driver - SOLD! 64 Chevy Short Step LS |
07-12-2021, 01:22 AM | #4 |
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Join Date: Jun 2016
Location: Phoenix AZ
Posts: 429
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Re: Loss of power on acceleration when warm, backfires a lot.
Do you have a way to see which cylinders are misfiring if they are misfiring?
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08-02-2021, 09:48 AM | #5 |
Registered User
Join Date: May 2013
Location: Mississippi
Posts: 501
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Re: Loss of power on acceleration when warm, backfires a lot.
Update:
Since I started the thread I have replaced the Camshaft position sensor, Crank sensor, and MAP sensor as these were all not replaced 5 years ago when I did the swap. Did not change anything. I never did have a ck engine light until two weeks ago I got P0175 rich on bank 2. Cleared the code came back a few days later. I have a constant 58 psi fuel pressure at idle. It seemed to only do this when under load and when the engine was warm. Even worse with the AC on. Then I replaced the Mass air flow sensor and still no change. Two days ago I replaced the spark plugs and plug wires again (were replaced when I did the swap 5 years ago). Now it seems like it is fixed. I have driven it about 60 miles and seems like the problem was solved. When I inspected the plugs they weren't fouled out/black and all 8 looked the same. If it comes back I will keep everyone posted. Thanks for the help.
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1987 R20 Suburban LQ4/4L80e swap: http://67-72chevytrucks.com/vboard/s...d.php?t=693824 |
08-02-2021, 12:43 PM | #6 |
Post Whore
Join Date: May 2015
Location: Alabama
Posts: 14,670
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Re: Loss of power on acceleration when warm, backfires a lot.
dont you just hate chasing a problem...then find its something simple
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Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver |
08-02-2021, 04:41 PM | #7 | |
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Join Date: May 2013
Location: Mississippi
Posts: 501
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Re: Loss of power on acceleration when warm, backfires a lot.
Quote:
My next two steps were to replace the throttle body, as I was thinking the Throttle position sensor was the problem. If that didn't fix it, I was going to pull the motor and fully build it and make it a beast.
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1987 R20 Suburban LQ4/4L80e swap: http://67-72chevytrucks.com/vboard/s...d.php?t=693824 |
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