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02-16-2014, 11:36 AM | #1 |
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Join Date: May 2013
Location: Mississippi
Posts: 501
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454 tbi won't idle when warmed up...
So I have been working at this for a while.
Problem is when truck is first started (cold) it runs fine, then when warmed up, and I let my foot off the gas pedal it dies. It will restart if I give it some gas ( press gas pedal just to be clear) while starting but then dies when I let off the pedal. When this started I was getting a code 44 lean exhaust so I replaced o2 sensor, fuel pressure regulator, fuel pump, and fuel filter, even a new gas tank and cap. And the problem remains. Prior to this I have replaced: erg valve, map sensor, coolant temp sensor, and cap,rotor,wires,plugs. Any ideas/suggestions?
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1987 R20 Suburban LQ4/4L80e swap: http://67-72chevytrucks.com/vboard/s...d.php?t=693824 |
02-16-2014, 01:13 PM | #2 |
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Location: Maryfield, Saskatchewan
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Re: 454 tbi won't idle when warmed up...
Have you checked / tested the air idle control? Could also possibly be a dead spot in the TPS? Just throwing out ideas, but from your post these might be all you have left to check.
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02-16-2014, 01:19 PM | #3 |
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Re: 454 tbi won't idle when warmed up...
I've been reading about checking the IAC and I don't have a tach to adjust the idle using the screw on the front of the tbi unit. Any other way to check it?
Thanks for the reply.
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1987 R20 Suburban LQ4/4L80e swap: http://67-72chevytrucks.com/vboard/s...d.php?t=693824 |
02-17-2014, 08:11 PM | #4 |
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Re: 454 tbi won't idle when warmed up...
Update, when the engine was cold it was running fine. I disconnected the IAC valve, and it has run fine ever since.
My guess is in the past I squirted some brake cleaner down into the IAC passage, and I may have ruined it. My thinking is when the motor is cold the pintle is retracted all the way. When it was supposed to extend, it went past where it was supposed to and was killing the motor.
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1987 R20 Suburban LQ4/4L80e swap: http://67-72chevytrucks.com/vboard/s...d.php?t=693824 |
02-18-2014, 02:54 AM | #5 | |
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Re: 454 tbi won't idle when warmed up...
Quote:
//RF
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"The Beast" 1975 Chevrolet C20 longbed 350/700R4! with 3inch body lift Dual Flowmasters Super 40's! TBI retrofit completed (2007-07-29) New 383CID (+030) 08-304-8 9.5:1CR x36,005 (2012-12-17) |
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02-18-2014, 03:14 AM | #6 |
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Location: Maryfield, Saskatchewan
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Re: 454 tbi won't idle when warmed up...
This is good to know. I am also having trouble with my TBI 454, but when cold. It acts like a poorly adjusted carb engine when cold.
I will be checking the same things out. Sensors, vac. leaks, and so on. I do have a minor coolant leak at the front of then intake against the drivers side head and wonder if that can cause my cold stumble issues.
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My Addiction: 1969 Pontiac Firebird 1983 K10 RCLB Silverado 6.2L Turbo 1986 K25 RCLB Sierra 1990 V3500 CCLB Silverado 1995 K2500 RCLB Cheyenne 6.5L Turbo |
02-19-2014, 01:23 PM | #7 |
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Join Date: Apr 2009
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Re: 454 tbi won't idle when warmed up...
Small Block Chevy / Almost the same as a 454
ALDL connector under dash How to calibrate the TBI IAC Motor 1-Engine warmed up, key OFF, tranny in PARK 2-Put a jumper wire from pin “A ” to pin “B” on the ALDL connector (should be the black wire & white wire) A metal paper clip works good for this. 3-Turn key to ON, do not start engine , wait 10 seconds. This will extend the IAC pintle and close off the air passage in the body of the TBI. Remove the electrical connection to the IAC by pulling it straight out. Turn the key to OFF and remove the jumper from the ALDL connector. 4-Start engine, and let it settle into idle speed. You may need to give it a little throttle to get it running. Connect the scanner to the ALDL and check the engine RPM. You want the engine RPM to be at least 125 rpm less than what the “target idle speed” is set for in the chip. Use the throttle screw to obtain the “125 rpm less” idle speed. Example:Target idle speed in the chip is 700 RPM less -125 minimum idle speed = 575 RPM 5-Turn engine OFF. Connect the IAC connector. 6-Start engine and run for seconds, turn engine OFF and wait at least 30 seconds. This will reset the IAC control. 7-Start engine, in PARK, let it idle. Idle speed should be close to the “target idle” set in the chip, if the IAC is being controlled by the ECM. Desert |
02-19-2014, 06:12 PM | #8 | |
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Join Date: May 2013
Location: Mississippi
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Re: 454 tbi won't idle when warmed up...
Quote:
I have a friend with a code reader who will let me borrow it.
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1987 R20 Suburban LQ4/4L80e swap: http://67-72chevytrucks.com/vboard/s...d.php?t=693824 |
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02-19-2014, 09:21 PM | #9 |
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Join Date: Jun 2012
Location: Minnesota
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Re: 454 tbi won't idle when warmed up...
Have you done the easy stuff like check for vacuum leaks? 8 out of 9 TBI idle and driveability complaints can be traced back to a vacuum leak. Stuck EGR, baked EGR base or intake gaskets, rotten hoses, worn throttle shaft bores. Don't relearn the IAC until you do or it will learn wrong and you'll really have trouble finding the problem.
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02-19-2014, 09:25 PM | #10 |
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Join Date: May 2013
Location: Mississippi
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Re: 454 tbi won't idle when warmed up...
Already replaced the tbi and adapter gaskets. Have replaced a few vacuum hoses. Where can I get the small hard vacuum lines that go from the tbi unit to the egr solonoid and from the solonoid to the valve.
They are really small and look like the are going to be hard to find.
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1987 R20 Suburban LQ4/4L80e swap: http://67-72chevytrucks.com/vboard/s...d.php?t=693824 |
02-20-2014, 01:16 AM | #11 |
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Join Date: Jun 2012
Location: Minnesota
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Re: 454 tbi won't idle when warmed up...
The hard plastic lines can be replaced with regular hose, so long as its not kinked and fits snug on the barbs.
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