73-87chevytrucks.com

73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 12gaige on October 23, 2015, 08:22:00 PM

Title: stalling at stops and idle
Post by: 12gaige on October 23, 2015, 08:22:00 PM
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.
Title: Re: stalling at stops and idle
Post by: Irish_Alley on October 23, 2015, 09:16:27 PM
Take it no CEL?
A vacuum leak can cause these problems
Title: Re: stalling at stops and idle
Post by: 12gaige on October 24, 2015, 02:36:09 PM
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
Title: Re: stalling at stops and idle
Post by: Irish_Alley on October 24, 2015, 03:54:28 PM
Does your CEL light up when you turn the key to the on position with the engine is off?
Title: Re: stalling at stops and idle
Post by: 12gaige on October 24, 2015, 04:04:57 PM
The light does work during bulb check.
Title: Re: stalling at stops and idle
Post by: Irish_Alley on October 24, 2015, 05:08:07 PM
http://forum.73-87chevytrucks.com/smforum/index.php?topic=29996.0
Title: Re: stalling at stops and idle
Post by: Dr_Snooz on October 25, 2015, 09:24:57 PM
^^ THAT is a handy link!
Title: Re: stalling at stops and idle
Post by: 12gaige on October 26, 2015, 07:23:06 AM
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.
Title: Re: stalling at stops and idle
Post by: Irish_Alley on October 26, 2015, 09:46:26 AM
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 
Title: Re: stalling at stops and idle
Post by: 12gaige on October 26, 2015, 11:45:26 AM
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.)
Title: Re: stalling at stops and idle
Post by: 12gaige on October 26, 2015, 06:28:03 PM
During open loop the o2 cross counts fine, but once in open loop the o2 only reads rich.
Title: Re: stalling at stops and idle
Post by: Irish_Alley on October 26, 2015, 06:32:58 PM
So does it have a problem when its cold or just after it warms up?
Title: Re: stalling at stops and idle
Post by: 12gaige on October 26, 2015, 07:17:47 PM
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.
Title: Re: stalling at stops and idle
Post by: Irish_Alley on October 26, 2015, 07:32:47 PM
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
Title: Re: stalling at stops and idle
Post by: frotosride on October 26, 2015, 08:30:18 PM
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.
Title: Re: stalling at stops and idle
Post by: frotosride on October 26, 2015, 08:38:52 PM
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.





Title: Re: stalling at stops and idle
Post by: 12gaige on October 27, 2015, 05:56:40 AM
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.
Title: Re: stalling at stops and idle
Post by: Irish_Alley on October 27, 2015, 09:26:50 AM
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
Title: Re: stalling at stops and idle
Post by: 12gaige on October 27, 2015, 06:58:49 PM
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.
Title: Re: stalling at stops and idle
Post by: Irish_Alley on October 27, 2015, 07:10:17 PM
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.
Title: Re: stalling at stops and idle
Post by: 12gaige on November 01, 2015, 07:22:22 PM
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.