new motor not running right - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sdime95 · 12-11-2009, 04:14 PM

ok so i decided to have my 260,000 mile 305 replaced with a new 305 and it idles fine but you give it a little gas in park neutral or drive and it studders like its running out of gas but one your going it runs fine in all gears and speeds my truck is a 87 silverado auto 2wd w/ new 305 any ideas on what it could be cause i have had my truck in the shop for a month now and am starting to get fed up

of mot have my truck and it not runing right thanks in advance

J_PEPIN87 · 12-11-2009, 06:22 PM

Have you checked the timing

Hottrucks · 12-11-2009, 06:38 PM

I got a nickle that says the plug wires are on wrong!!

Kixwy2 · 12-12-2009, 04:07 AM

Is it a stumble off idle? I've had that... you may have to adjust the carb to fix that.

68 TT · 12-12-2009, 10:53 AM

Put a vacuum gauge on it. It should be pulling close to 24 inches in a stock mid 80's 305 like my 83 did. You could have a big vacuum leak.

Next check to make sure the timing is right and all the plug wires are in the right order. Its easy to get two crossed over.

Then check to make sure you don't have a fuel delivery problem. Make sure it has fuel pressure at the carb and full fuel bowls. It could be a lean stumble off idle caused by not enough fuel volume or pressure getting to the carb.

**old Rusty C10** · 12-12-2009, 11:52 AM

stupid question its got a new gas filter ? id also check that and make sure its ok in addition to what the others suggested

sdime95 · 12-12-2009, 05:02 PM

sorry i didn't say it's a TBI not carb. fuel filter is new, timing is good, new o2 sensor. still feels like its spuddering but now it doesnt do it all the time only on occasion aghhhhhh!

87 STEPPER · 12-12-2009, 05:40 PM

You say the timing is good but did you set the base timing with the EST disconnected ?

3r!c84 · 12-12-2009, 06:55 PM

i got a dumb question.why did you get a 305? why didnt you upgrade to a 350?

68 TT · 12-14-2009, 12:32 PM

Quote:

Originally Posted by sdime95

sorry i didn't say it's a TBI not carb. fuel filter is new, timing is good, new o2 sensor. still feels like its spuddering but now it doesnt do it all the time only on occasion aghhhhhh!

That makes things a little different. Since it is TBI you need to do a little work to get a fuel pressure gauge on it but you need to know what the fuel pressure is to make sure you have enough. 10 pounds or under and you would be lucky if it ran at all. Shoot for 13 to 15 psi.

You still need to make sure the basics are good (vacuum, spark, plugs, wire routing, etc...) but you should also get an ALDL connector cable to data log what your ECM sees. It will help you out tremendously. thirdgen.org is packed full of info on getting started with data logging.

sdime95 · 12-14-2009, 10:51 PM

thanks im taking it in tomorrow to the guy who put it in i will make sure to have him check these things any other ideas would be great

12-11-2009, 04:14 PM	#1
sdime95 Registered User Join Date: Sep 2009 Location: Littleton, CO Posts: 33	new motor not running right ok so i decided to have my 260,000 mile 305 replaced with a new 305 and it idles fine but you give it a little gas in park neutral or drive and it studders like its running out of gas but one your going it runs fine in all gears and speeds my truck is a 87 silverado auto 2wd w/ new 305 any ideas on what it could be cause i have had my truck in the shop for a month now and am starting to get fed up of mot have my truck and it not runing right thanks in advance __________________ 1984 Sierra 1/2 ton 4x4 swb 1987 Silverado 2wd swb 3/4 drop

12-11-2009, 06:22 PM	#2
J_PEPIN87 Registered User Join Date: Sep 2008 Location: PASADENA,TX Posts: 206	Re: new motor not running right Have you checked the timing

12-11-2009, 06:38 PM	#3
Hottrucks Redefining LowBudget Join Date: Mar 2009 Location: lebanon Cow Hampshire Posts: 4,538	Re: new motor not running right I got a nickle that says the plug wires are on wrong!! __________________ 1970 C10 CST fleetside 472 ....big dreams little cash... http://67-72chevytrucks.com/vboard/s...d.php?t=335721 SunShine Syndicate.. Mikes Sandwich Fair Run OCT 8th 2011 http://www.thesandwichfair.com/html/...auto_show.html

12-12-2009, 04:07 AM	#4
Kixwy2 Registered User Join Date: Dec 2007 Location: Central Coast, CA Posts: 177	Re: new motor not running right Is it a stumble off idle? I've had that... you may have to adjust the carb to fix that. __________________ 1974 GMC C-10; my new addiction 1998 4 Runner; daily driver

12-12-2009, 10:53 AM	#5
68 TT Still plays with trucks Join Date: Jul 2009 Location: Spokane, WA Posts: 3,556	Re: new motor not running right Put a vacuum gauge on it. It should be pulling close to 24 inches in a stock mid 80's 305 like my 83 did. You could have a big vacuum leak. Next check to make sure the timing is right and all the plug wires are in the right order. Its easy to get two crossed over. Then check to make sure you don't have a fuel delivery problem. Make sure it has fuel pressure at the carb and full fuel bowls. It could be a lean stumble off idle caused by not enough fuel volume or pressure getting to the carb. __________________ miSSed opportunity - ground up creation of an AWD 1994 454 SS that never was http://67-72chevytrucks.com/vboard/s...d.php?t=795577 69 C10 shortbed stepside 400 small block - built like what a super sport truck could have been 69 K20 lwb TBI 350 4L60E NP208 14-bolt Dana-44 w/disc 68 Camaro SS / RS 500hp 439 inch roller cam big block 4L80E 79 Malibu TPI 350 4L60 w/ Z28 steering & sway bars

12-12-2009, 11:52 AM	#6
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,302	Re: new motor not running right stupid question its got a new gas filter ? id also check that and make sure its ok in addition to what the others suggested __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

12-12-2009, 05:02 PM	#7
sdime95 Registered User Join Date: Sep 2009 Location: Littleton, CO Posts: 33	Re: new motor not running right sorry i didn't say it's a TBI not carb. fuel filter is new, timing is good, new o2 sensor. still feels like its spuddering but now it doesnt do it all the time only on occasion aghhhhhh! __________________ 1984 Sierra 1/2 ton 4x4 swb 1987 Silverado 2wd swb 3/4 drop

12-12-2009, 05:40 PM	#8
87 STEPPER STILL PLAYS WITH TRUX Join Date: Nov 2002 Location: Melbourne, Fla. Posts: 2,764	Re: new motor not running right You say the timing is good but did you set the base timing with the EST disconnected ? __________________ ~~Bruce~~ MY 87 STEPPER MY 99 2D/WD TAHOE

12-12-2009, 06:55 PM	#9
3r!c84 Badass Join Date: Jan 2009 Location: lox. fl Posts: 4,586	Re: new motor not running right i got a dumb question.why did you get a 305? why didnt you upgrade to a 350? __________________ Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90

12-14-2009, 10:51 PM	#11
sdime95 Registered User Join Date: Sep 2009 Location: Littleton, CO Posts: 33	Re: new motor not running right thanks im taking it in tomorrow to the guy who put it in i will make sure to have him check these things any other ideas would be great __________________ 1984 Sierra 1/2 ton 4x4 swb 1987 Silverado 2wd swb 3/4 drop



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