73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 12gaige on October 23, 2015, 08:22:00 PM
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I have begun to rip my hair out. Have an 87 r1500 2wd 305 tbi. My problem is the truck will stall when coming to a stop, slow turns, and sometimes at idle. I have replaced the tps, iac, egr, and even swapped complete tbi units from other trucks that run perfectly. No matter what i do it will keep stalling, unless i manually bend the throttle shaft to make it idle high (sounds somewhere between 1600 to 2000 rpm). Or if i two foot drive it and make it idle high. No codes, any help would be appreciated. I am about tempted to rip the top end off and carb it.
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Take it no CEL?
A vacuum leak can cause these problems
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No cel and no leaks that i can find. Changed the tbi to intake gasket. Egr gasket. Ive sprayed with carb spray and water multiple times and can not find any kind of a leak
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Does your CEL light up when you turn the key to the on position with the engine is off?
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The light does work during bulb check.
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http://forum.73-87chevytrucks.com/smforum/index.php?topic=29996.0
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^^ THAT is a handy link!
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Yes it is. I may have it pin pointed it down to the distributor. ALL of the sensors are within spec, i will be pulling one out of my perfectly running plow trucks for testing, and if it helps i am going to pick a brand new one up at the dealership.
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The distributor on these things do do a lot. They give the signal for fuel signal and of course spark. It will be something new if it causes it to stall to me. Keep us updated
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Finally got a code. I believe it was 34 (forgot to write it down) MAP voltage low. I tried to reference the post you replied with. But map is teading 30kpa at idle and around 1.0 volt (8.5 to 1.2 volts.)
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During open loop the o2 cross counts fine, but once in open loop the o2 only reads rich.
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So does it have a problem when its cold or just after it warms up?
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It doesn't usually stall when its cold. It has before but, the first minute or two after start up is usually safe to not stall.
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What. I took that as it normally doesn't stall when cold but after the first couple minutes its safe note not stall. When does it stall? Lol
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I chased this problem for years and came to find that i had to raise the idel because everything had worn over the years. Let me guess a guaranteed stall is in reverse with the wheel turned?
Give me a few to find the article but it is in the tech pages if you find it before me.
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http://forum.73-87chevytrucks.com/smforum/index.php?topic=21039.0
Got it!!! Follow this. The first time I did it I didn't have a tach because it wasn't a factory option for my truck but so I did it by sound. I did get a tach soon after and it was spot on. The biggest part is actually the load at idel. I replaced the same things except instead of the intake !ainfold ( no vaccum leaks) I replaced my alternator because of a fluke and thinking it was a voltage drop causing the stall. This will like fix the issue. I'd be blown away if it doesn't. You will need a small torques bit to do the adjust!entire and a drill. You can get the idle screw plug out with a punch to off center it. Maybe even a screen and hammer.
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Sorry for the wording. The truck will usually not stall the first cold start of the day for the firt minute. after i leave the neighborhood the truck will stall whenever i stop.
Another piece of information i should let you know is the previous owner i bought the truck from had turned up the idle so it wouldnt stall. It was set somewhere around 2000+ and kept eating u-joints. I had a couple tbi units lying around so i kept swapping between them to fine one that runs better.
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Open loop is what the engine runs the engine when cold then it goes into closed when the engine meets certain requirements.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=31489.msg264376#msg264376
As for what's causing it to stall is still a mystery but atleast we are getting somewhere
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Yeah i understand what closed and open loop are. I dont understand how the o2 sensor cross counts as soon as it is started but during closed it only reads rich.
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If I understand what your saying my take on it is the ecm ignores the od sensor till a certain temp is reached. Then the o2 gives its reading.
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Found the problem. The distributor magnets were not strong enough. I changed the ignition modual under the cab, did nothing. Replaced the coil too, did nothing. Then i bit the bullet and went down to the dealership to pick up the new distributor they had in stock, and new cap and rotor. Now the truck never stalls.