Question on 305 problems from new guy - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Jon86silverado · 10-19-2004, 07:01 PM

I have an 86 305 in my 1/2 ton 2wd silverado. last summer I started to get bad bad gas milage i went from 15 to 8mpg then it started to idle rough so I put plugs wires cap rotor and a coil in. that didn't work. so then I put an egr valve in and it helped some it still gets bad milage and idles ruff and after my 2hour drive to college it misses. I have heard of head problems in this year is that what it could be?

*1FaastC10* · 10-19-2004, 08:47 PM

my ESC went bad in my 86 C10, and caused similar symptoms to what you described. it would miss intermittently, and sometimes not start. finally it died, and after putting 2 700R4s in it, and having to swap distributors, i decided it was time to go a different route. that's where my 4x4 conversion started.

Jon86silverado · 10-19-2004, 09:30 PM

Thanks for the help Can I dissconnect the esc at all and if so will it effect the motor any other way.

**N2TRUX** · 10-19-2004, 09:36 PM

Quote:

Originally Posted by Jon86silverado

Thanks for the help Can I dissconnect the esc at all and if so will it effect the motor any other way.

You can't just disconnect it, because it controls the distributor. ESC stands for electronic spark control. The most common way to defeat it is replace the ESC distributor with an HEI distributor....

BTW-Welcome to the forum. We are alawys glad to see new folks come through...

**swervin ervin** · 10-19-2004, 09:59 PM

You can do away with the ESC.

http://www.73-87.com/7387garage/drivetrain/escrepl.htm

If I were guessing, I'd say you have carb troubles.

Oh, and welcome to our little home away from it all.

Destructo · 10-19-2004, 11:08 PM

well, you can sorta just disconnect it, the person who did the engine swap on my friends camaro didn't swap everything over and its an 87 so it had ESC and it was disconnected mainly, until we went to the yard and picked up an HEI for him I just set his timing to where it ran ok, but power sucked and mileage sucked because it was basically stuck at 10 degrees timing no matter what.

SanitysBane · 10-19-2004, 11:35 PM

arg when wil y'all listen? all u need to do is disconect the knox sensor on the side of the block, witht that done, the ESC won't do anything at all. the ESC is still hooked up on my truck, and i havn't had any problems with it(454 inplace of the 305) if you don't belive me, read the HELMS shop manual,

c-1072 · 10-19-2004, 11:44 PM

You might want to check you distributor , loose shaft bushings or forzen advance fly wieghts ( under rotor )

Jon86silverado · 10-20-2004, 12:20 AM

Thanks for all the help I will try all those things and see what works! maybe that 305 will get some milage again.

loweredd · 10-20-2004, 08:21 PM

Not to rain on your parade, but my 76,000 mile 305 in my 79 Imp just ate the cam and lifters. #5 and #6 cam lobes were completely round. It would run great, but idle crappy. The lifters were no longer spinning in the lifter bores, and wiped the lobes off the cam. I get the engine back from the machine shop tomorrow, after a full rebuild.

*1FaastC10* · 10-20-2004, 11:46 PM

Quote:

Originally Posted by SanitysBane

arg when wil y'all listen? all u need to do is disconect the knox sensor on the side of the block, witht that done, the ESC won't do anything at all. the ESC is still hooked up on my truck, and i havn't had any problems with it(454 inplace of the 305) if you don't belive me, read the HELMS shop manual,

some of us dont like a cluttered up mess under our hood. the more you reomve the less potential problems you have with shorts, and the easier they are to diagnose when you do have them.

SanitysBane · 10-20-2004, 11:57 PM

its an easy fix, incase you don't have the funds to get a new dizzy, like me

10-19-2004, 07:01 PM	#1
Jon86silverado Registered User Join Date: Sep 2004 Location: Princeton Posts: 25	Question on 305 problems from new guy I have an 86 305 in my 1/2 ton 2wd silverado. last summer I started to get bad bad gas milage i went from 15 to 8mpg then it started to idle rough so I put plugs wires cap rotor and a coil in. that didn't work. so then I put an egr valve in and it helped some it still gets bad milage and idles ruff and after my 2hour drive to college it misses. I have heard of head problems in this year is that what it could be?

10-19-2004, 11:35 PM	#7
SanitysBane Registered User Join Date: May 2004 Location: Lubbock, Texas Posts: 2,121	arg when wil y'all listen? all u need to do is disconect the knox sensor on the side of the block, witht that done, the ESC won't do anything at all. the ESC is still hooked up on my truck, and i havn't had any problems with it(454 inplace of the 305) if you don't belive me, read the HELMS shop manual, __________________ '96 Nissan Pathfinder '02 Firebird Trans Am. '88 K5 Blazer

10-19-2004, 11:44 PM	#8
c-1072 Registered User Join Date: Sep 2004 Location: rochester NY Posts: 777	Bad gas milage You might want to check you distributor , loose shaft bushings or forzen advance fly wieghts ( under rotor )

10-20-2004, 11:57 PM	#12
SanitysBane Registered User Join Date: May 2004 Location: Lubbock, Texas Posts: 2,121	its an easy fix, incase you don't have the funds to get a new dizzy, like me __________________ '96 Nissan Pathfinder '02 Firebird Trans Am. '88 K5 Blazer

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10-19-2004, 08:47 PM	#2
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,400	my ESC went bad in my 86 C10, and caused similar symptoms to what you described. it would miss intermittently, and sometimes not start. finally it died, and after putting 2 700R4s in it, and having to swap distributors, i decided it was time to go a different route. that's where my 4x4 conversion started.

10-19-2004, 09:30 PM	#3
Jon86silverado Registered User Join Date: Sep 2004 Location: Princeton Posts: 25	Thanks for the help Can I dissconnect the esc at all and if so will it effect the motor any other way.

10-19-2004, 09:59 PM	#5
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	You can do away with the ESC. http://www.73-87.com/7387garage/drivetrain/escrepl.htm If I were guessing, I'd say you have carb troubles. Oh, and welcome to our little home away from it all. __________________ Mike 1985 Chevy C-10

10-19-2004, 11:08 PM	#6
Destructo Registered User Join Date: Sep 2003 Location: Lewisville, NC Posts: 1,836	well, you can sorta just disconnect it, the person who did the engine swap on my friends camaro didn't swap everything over and its an 87 so it had ESC and it was disconnected mainly, until we went to the yard and picked up an HEI for him I just set his timing to where it ran ok, but power sucked and mileage sucked because it was basically stuck at 10 degrees timing no matter what. __________________ 1985 Scottsdale Shortbed 4x4 Stout 350 with some "upgrades"-700r4-33x12.5" Mud Tires, Warn 8274-50 winch. 2005 Chevrolet Colorado Regular Cab 2wd 4-banger, 5 speed, Street Pack with 3.73 axle.

10-20-2004, 12:20 AM	#9
Jon86silverado Registered User Join Date: Sep 2004 Location: Princeton Posts: 25	Thanks for all the help I will try all those things and see what works! maybe that 305 will get some milage again.

10-20-2004, 08:21 PM	#10
loweredd www.loweredd.com Join Date: Aug 2002 Location: Struble IA Posts: 808	Not to rain on your parade, but my 76,000 mile 305 in my 79 Imp just ate the cam and lifters. #5 and #6 cam lobes were completely round. It would run great, but idle crappy. The lifters were no longer spinning in the lifter bores, and wiped the lobes off the cam. I get the engine back from the machine shop tomorrow, after a full rebuild.



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