need some engine help! 86. 350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

penaduny · 07-10-2005, 03:37 PM

heres my problem. my truck will idle fine, rev fine. nothing out of the ordinary. if i go do drive it around, after about a half a mile, i get horrible hesitation, thing almost dies, if i get on it, it will die, and my brakes really dont work at all. so i came to the conclusion of a vacuum problem.. so i changed a bunch of vacuum lines, put a new brake booster in for the hell of it, checked everything else i could. and nothing has changed. the truck pretty much started doing this out of nowhere. i put a new motor/trany in about a year ago, had the carb rebuit at the same time. so now i take it to my freinds shop to see if they can find out whats wrong. they said it was the carb. so i got it home. took the carb off and brought it to the place i had reuild it, they checked it all out, hooked it up to this motor they have on a dyno, and everything checked out perfectly fine. so im stumped. put the carb back on. double check everything, every vacuum line. truck starts right up. but still. same thing.

more backround: this has all the cali emissions bull**** on the motor. when i put the new 350 in i put almost all new parts on.

anybody have some sugestions for me?

any help would be greatly appreciated.

*rage'nrat638* · 07-10-2005, 07:23 PM

sounds like a intake gasket problem........
spray carb or brake cleaner around the intake while running .....
deffenently a vacuum problem......
check the line going to the trans.
also could be a vacuum /temp operated swiych.........

wish i were ther to help we would fix it.....your pal mark

ureckme · 07-11-2005, 01:50 AM

Fuel filter 1 put a vacume gauge on it 2 and check fuel pressure

penaduny · 07-11-2005, 02:41 AM

k. i checked the intake manifold. thats fine.
checked vacuum pressure. thats fine also, at least when its idlling, there is plenty of vacuum.

vacuum advance is fine, so is the line going to the tranny.

the ploblem only occurs when there is a load on the engine. i can rev it very high (in neutral), that is all fine. just after ive drivin about 100 feet, its like i loose all vacuum, the brakes stop working and it starts to hesitate and try to die on me.

i worked on it for a hour or so tonight.. no progress at all on the problem. i almost wish this was a major problem that i have to pull the engine for, i dont car what the solution is. i just want to know whats wrong.

its getting very frustarating when i am just wasting time and money, and nothing changes. especialy when i can hop in my truck right now, and with half a crank the engine starts right up. its soooo depressing.

sorry for the rant. im just.. ehh.. depresed i guess.

tomorrow, im going to start replacing every part on my motor with a vacuum line going to it untill the problem stops.

norville · 07-11-2005, 07:20 AM

Timing OK???

EGR?? I have a toy that had an egr leak would run great for 15 min. then I couldn't keep in drive. When stopping I had to put it in nutral. Bad egr gasket...

bob

penaduny · 07-11-2005, 11:47 AM

yea. the timing is fine.. the egr valve is new. but ill check it out anyways.

thanks.

anybody sugest anything else?

Slonaker · 07-11-2005, 11:56 AM

I had a lot of problems with vacuum leaks at my EGR valve on my '86 305. It uses a spacer, and the spacer was so rusty and pited it would leak even with new gaskets. I finally pulled the spacer off one at a junkyard that was just surface rusted, cleaned it up, and got it to quit leaking.

I believe that you can get a masive vacuum leak if the EGR sticks open. Makes sure it is opening and closing properly and not sticking. On mine, I can reach underneath it and move it up and down.

Slonaker

EDIT: I guess it couldn't hurt to make sure it isn't being pulled open and held open by an incorrectly routed vacuum hose.

**Boog** · 07-11-2005, 08:19 PM

Also the vacumn test: hook the vacumm gauge to a port and rev and hold the engine at around 1500 rpm for several minutes and observe the gauge reading. It should level off and hold a pretty steady vacumn reading. If while at that steady rpm the vacumn starts dropping off this indicates a possible blockage in the exhaust system.
I'm curious as to what kind of exhaust system you have on it. Original converter and muffler?
If the pipe is partially blocked inside it will exhibit much the same symptoms as you've stated: starts fine and runs out so far and falls on it's face. If you suspect the exhaust system might be the problem you can loosen the headpipes a little bit to allow it to breath better and try driving it like that.
Process of elimination.

Russell · 07-11-2005, 08:47 PM

It sounds like a fuel system issue to me. Make sure that you check the flow rate of the fuel pump, not just the pressure. The part that raises the fuel pump flag is how it is fine in park, but sucks as soon as you put a load on an engine. Its not too terribly uncommong for a pump to produce healthy PSI numbers, but very little flow rate so the engine starves when it does not get enough fuel under a load.

ureckme · 07-11-2005, 09:50 PM

I said fuel problem befor but Boog's idea is a very good one ( pluged pipes ) now I just had trouble like this and it was the coil cover on the HEI had come loose and it would rev fine in N but in gear it would go to 2000rpm's and fall on it's face. Matt

Brad_Olson · 07-12-2005, 08:32 AM

Speaking of vacuum, does your engine have any thermal vacuum switches? If nothing else works I'm wondering if a bad switch could be signaling the EGR valve to let too much exhaust into the intake. Just a WAG for a Tuesday morning...

Brad

07-10-2005, 03:37 PM	#1
penaduny Registered User Join Date: Sep 2004 Posts: 29	need some engine help! 86. 350 heres my problem. my truck will idle fine, rev fine. nothing out of the ordinary. if i go do drive it around, after about a half a mile, i get horrible hesitation, thing almost dies, if i get on it, it will die, and my brakes really dont work at all. so i came to the conclusion of a vacuum problem.. so i changed a bunch of vacuum lines, put a new brake booster in for the hell of it, checked everything else i could. and nothing has changed. the truck pretty much started doing this out of nowhere. i put a new motor/trany in about a year ago, had the carb rebuit at the same time. so now i take it to my freinds shop to see if they can find out whats wrong. they said it was the carb. so i got it home. took the carb off and brought it to the place i had reuild it, they checked it all out, hooked it up to this motor they have on a dyno, and everything checked out perfectly fine. so im stumped. put the carb back on. double check everything, every vacuum line. truck starts right up. but still. same thing. more backround: this has all the cali emissions bull**** on the motor. when i put the new 350 in i put almost all new parts on. anybody have some sugestions for me? any help would be greatly appreciated.

07-11-2005, 01:50 AM	#3
ureckme ureckmefixit2@cox.net Join Date: Dec 2004 Location: Mesa AZ. (Phoenix) Posts: 1,284	Fuel filter 1 put a vacume gauge on it 2 and check fuel pressure __________________ That's U RECK ME FIX it 2 74 Chevy Short Bed 355ci Sportsman II 64cc Angle Plug Crower Custom Grind .462in .486ex Dyno Test 422hp @ 5600 And it's got a Holley 3.73 Gears 12 Bolt 3.73 w/Posi 700R4 Going In I'm a Body Man So There! That's why it's not painted

07-11-2005, 07:20 AM	#5
norville Senior Member Join Date: Jun 2004 Location: Mountain Top, Pa Posts: 323	Timing OK??? EGR?? I have a toy that had an egr leak would run great for 15 min. then I couldn't keep in drive. When stopping I had to put it in nutral. Bad egr gasket... bob __________________ 1986 C10 Scottsdale 5.3, TH400

07-11-2005, 11:56 AM	#7
Slonaker Insert Witty Text Here Join Date: Oct 2002 Location: San Antonio, TX Posts: 3,415	I had a lot of problems with vacuum leaks at my EGR valve on my '86 305. It uses a spacer, and the spacer was so rusty and pited it would leak even with new gaskets. I finally pulled the spacer off one at a junkyard that was just surface rusted, cleaned it up, and got it to quit leaking. I believe that you can get a masive vacuum leak if the EGR sticks open. Makes sure it is opening and closing properly and not sticking. On mine, I can reach underneath it and move it up and down. Slonaker EDIT: I guess it couldn't hurt to make sure it isn't being pulled open and held open by an incorrectly routed vacuum hose. __________________ '86 Chevy C10 (Sold 04/19/13 ) Stock '01 Silverado Last edited by Slonaker; 07-11-2005 at 11:59 AM.

07-11-2005, 08:19 PM	#8
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,535	Also the vacumn test: hook the vacumm gauge to a port and rev and hold the engine at around 1500 rpm for several minutes and observe the gauge reading. It should level off and hold a pretty steady vacumn reading. If while at that steady rpm the vacumn starts dropping off this indicates a possible blockage in the exhaust system. I'm curious as to what kind of exhaust system you have on it. Original converter and muffler? If the pipe is partially blocked inside it will exhibit much the same symptoms as you've stated: starts fine and runs out so far and falls on it's face. If you suspect the exhaust system might be the problem you can loosen the headpipes a little bit to allow it to breath better and try driving it like that. Process of elimination. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

07-10-2005, 07:23 PM	#2
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	sounds like a intake gasket problem........ spray carb or brake cleaner around the intake while running ..... deffenently a vacuum problem...... check the line going to the trans. also could be a vacuum /temp operated swiych......... wish i were ther to help we would fix it.....your pal mark

07-11-2005, 02:41 AM	#4
penaduny Registered User Join Date: Sep 2004 Posts: 29	k. i checked the intake manifold. thats fine. checked vacuum pressure. thats fine also, at least when its idlling, there is plenty of vacuum. vacuum advance is fine, so is the line going to the tranny. the ploblem only occurs when there is a load on the engine. i can rev it very high (in neutral), that is all fine. just after ive drivin about 100 feet, its like i loose all vacuum, the brakes stop working and it starts to hesitate and try to die on me. i worked on it for a hour or so tonight.. no progress at all on the problem. i almost wish this was a major problem that i have to pull the engine for, i dont car what the solution is. i just want to know whats wrong. its getting very frustarating when i am just wasting time and money, and nothing changes. especialy when i can hop in my truck right now, and with half a crank the engine starts right up. its soooo depressing. sorry for the rant. im just.. ehh.. depresed i guess. tomorrow, im going to start replacing every part on my motor with a vacuum line going to it untill the problem stops.

07-11-2005, 11:47 AM	#6
penaduny Registered User Join Date: Sep 2004 Posts: 29	yea. the timing is fine.. the egr valve is new. but ill check it out anyways. thanks. anybody sugest anything else?

07-11-2005, 08:47 PM	#9
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	It sounds like a fuel system issue to me. Make sure that you check the flow rate of the fuel pump, not just the pressure. The part that raises the fuel pump flag is how it is fine in park, but sucks as soon as you put a load on an engine. Its not too terribly uncommong for a pump to produce healthy PSI numbers, but very little flow rate so the engine starves when it does not get enough fuel under a load. __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

07-11-2005, 09:50 PM	#10
ureckme ureckmefixit2@cox.net Join Date: Dec 2004 Location: Mesa AZ. (Phoenix) Posts: 1,284	I said fuel problem befor but Boog's idea is a very good one ( pluged pipes ) now I just had trouble like this and it was the coil cover on the HEI had come loose and it would rev fine in N but in gear it would go to 2000rpm's and fall on it's face. Matt __________________ That's U RECK ME FIX it 2 74 Chevy Short Bed 355ci Sportsman II 64cc Angle Plug Crower Custom Grind .462in .486ex Dyno Test 422hp @ 5600 And it's got a Holley 3.73 Gears 12 Bolt 3.73 w/Posi 700R4 Going In I'm a Body Man So There! That's why it's not painted

07-12-2005, 08:32 AM	#11
Brad_Olson Active Member Join Date: Mar 2005 Location: Stoughton, WI Posts: 187	Speaking of vacuum, does your engine have any thermal vacuum switches? If nothing else works I'm wondering if a bad switch could be signaling the EGR valve to let too much exhaust into the intake. Just a WAG for a Tuesday morning... Brad



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