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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: dylan.lauenstein on August 30, 2014, 11:57:42 am

Title: 87 305 TBI Issues
Post by: dylan.lauenstein on August 30, 2014, 11:57:42 am

Alright my 305 has been being pretty temperamental. For 20 mins it will idle fine, but after that it will idle rough and die out on its own. But once your into the throttle it runs fine. Any ideas?

Title: Re: 87 305 TBI Issues
Post by: 78BIG-TEN on August 30, 2014, 01:18:03 pm

sounds like a vacumn leak,base gaskets are prone to leak

Title: Re: 87 305 TBI Issues
Post by: dylan.lauenstein on August 30, 2014, 04:14:19 pm

Another thing is the first time you start it it will idle fine the whole time but once you drive it and shut it off once it won't idle very well

Title: Re: 87 305 TBI Issues
Post by: Irish_Alley on August 30, 2014, 10:42:25 pm

im with 78 sounds like a vacuum leak. and its something that gets worse when the metal expands after getting warm. need to test for a leak with carb spray or a propane torch w/o lighting the gas turn it on and move it around the gaskets after the engine is warm and running

Title: Re: 87 305 TBI Issues
Post by: roundhouse on August 31, 2014, 12:05:00 am

What codes are in the computer ?

Title: Re: 87 305 TBI Issues
Post by: roundhouse on September 01, 2014, 05:47:53 pm

Sounds like once it warms up and switches to the sensors telling the computer what to do is when the problems start

Try unplugging the temp sensor to the computer and see what happens

But pull the codes first

Title: Re: 87 305 TBI Issues
Post by: 78BIG-TEN on September 01, 2014, 07:12:55 pm

possible sticking IAC also

Title: Re: 87 305 TBI Issues
Post by: Irish_Alley on September 01, 2014, 09:45:04 pm

The temp sensor is used only when the engine is cold. After it warms up it tells the ecm the the o2 sensor kicks in

To test the coolant sensor, unplug the wire connector and test the resistance across the two terminals of the SENSOR with an ohm meter.

The sensor screws into the intake manifold, on the front passenger side, by the thermostat housing.

Coolant sensor approximate resistance specifications:
177 ohms @ 212 deg. F. or 100 deg. C.
241 ohms @ 194 deg. F. or 90 deg. C.
332 ohms @ 176 deg. F. or 80 deg. C.
467 ohms @ 158 deg. F. or 70 deg. C.
667 ohms @ 140 deg. F. or 60 deg. C.
973 ohms @ 122 deg. F. or 50 deg. C.
1188 ohms @ 113 deg. F. or45 deg. C.
1459 ohms @ 104 deg. F. or 40 deg. C.
1802 ohms @ 95 deg. F. or 35 deg. C.
2238 ohms @ 86 deg. F. or 30 deg. C.
2796 ohms @ 77 deg. F. or 25 deg. C.
3520 ohms @ 68 deg. F. or 20 deg. C.
4450 ohms @ 59 deg. F. or 15 deg. C.
5670 ohms @ 50 deg. F. or 10 deg. C.
7280 ohms @ 41 deg. F. or 5 deg. C.
9420 ohms @ 32 deg. F. or 0 deg. C.
12300 ohms @ 23 deg. F. or -5 deg. C.
16180 ohms @ 14 deg. F. or -10 deg. C.
21450 ohms @ 5 deg. F. or -15 deg. C.
28680 ohms @ -4 deg. F. or -20 deg. C.
52700 ohms @ -22 deg. F. or -30 deg. C.
100700 ohms @ -40 deg. F. or - 40 deg. C.