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Old 05-23-2011, 05:42 PM
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TBI 350 Idle issues...again...

1994 K1500 tbi 350 280,000 miles. 8,000 on new engine

wants to lope and die at idle.
new egr
new iac
new dist.
new pcv
rebuilt TBI
new knock sensor
new computer
tried all kinds of base timing levels

i am thinking it could be fuel pressure? (replaced pump 40,000 miles ago)
worn throttle shafts?
TPS?
Some even say oil pressure switch. I replaced when i put new engine in.

i am at my wits end with this thing.
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Old 05-23-2011, 06:44 PM
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Quote:
Originally Posted by shane.,herold
1994 K1500 tbi 350 280,000 miles. 8,000 on new engine

wants to lope and die at idle.
new egr
new iac
new dist.
new pcv
rebuilt TBI
new knock sensor
new computer
tried all kinds of base timing levels

i am thinking it could be fuel pressure? (replaced pump 40,000 miles ago)
worn throttle shafts?
TPS?
Some even say oil pressure switch. I replaced when i put new engine in.

i am at my wits end with this thing.
Read this:

http://www.gmcmidwestclassics.org/We...0the%20TBI.pdf

Did you follow this proceedure?

Bogie
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Old 05-23-2011, 08:03 PM
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When you set the timing did you disconnect the EST connector. It should be on 0 but you can go up to 4
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Old 05-24-2011, 12:18 AM
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yes i disconnected the wire to set timing, and anyone that says you can only go 4 degrees is wrong. I have ran anywhere from 0 to 16 and the truck ran fine at all. I keep it just over 10 and it is snappy this way.

i replaced the TBI base gasket today. All of the calibrating on the link is good information, but highly unnecessary. A quick disconnection of the battery cable and a couple start ups for it to learn itself and it will run fine. My problem is about 60% of the time. I can put the idle screw anywhere and the IAC will make it idle fine. when it dies it will fire right back up and run fine for awhile.
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Old 05-24-2011, 12:33 AM
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egr

check your egr valve. even though its brand new. it may be sticking open. this would cause it to run fine except at idle or low rpm.
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Old 05-24-2011, 02:51 PM
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wel, when closing the hood in the dark while the truck was running, i noticed some small sparks jumping from the header to a dangling itty bitty ground wire out of a loom by the bell housing. I hooked it up and the truck now purrs like a kitten. And my winshield wipers work again. I have been fighting this problem on and off for a YEAR!! one tiny little wire should not be sooo important for my truck to run right. Thinking i need to make sure there arent any other ones not connect making this one relied upon too much.
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Old 05-24-2011, 04:10 PM
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lol

make sure u got a good ground from the battery to the motor. then one from the motor to the firewall which is the one u hooked back up. and there should be one more from the frame to the body. bad ground can cause alot of wierd issues.
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Old 05-24-2011, 05:27 PM
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ground

my battery cable goes to block, 1 from body to frame, body to engine and the one that was hanging came out of one of the looms back there. not sure what it goes to
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