Idle problems

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Jun 24, 2008 | 09:58 PM

lt1350

Thread Starter

Cruising

Joined: Dec 2007

Posts: 12

Likes: 0

From: Maryland

Idle problems

My vette wont idle when its warm. It konks out at stop signs unless I keep my on the gas. The problem seems to be getting worse with time. It idles fine when cold.

Its a 71 LT1 with wih a Holly carb. Any ideas?

thanks

Jun 24, 2008 | 10:24 PM

Durango_Boy

Team Owner

Joined: Aug 2006

Posts: 24,125

Likes: 15

From: Columbia Missouri

Sounds like your choke is not adjusted properly anymore. Have a look at the choke. Make sure it's closed when cold, and open when hot.

Jun 25, 2008 | 05:48 AM

Matt Gruber

Race Director

Joined: Oct 2000

Posts: 14,954

Likes: 79

From: central FL, near the beach.

soak the metering block in carb cleaner

Jun 25, 2008 | 06:40 AM

Bangkok Dean

Le Mans Master

Joined: Jan 2004

Posts: 8,295

Likes: 30

From: one night in Bangkok you are never lonely

Sounds like vapor lock. Are you running a return line from the fuel pump to the tank? The return line keeps the fuel flowing and cool so there is no boiling in the line. I even run an in tank fuel pump and a return line from the carb to the tank. Over here the traffic lights are long and temps are always over 95* during the days. With out the above the idle will drop to stall at lights.

Jun 25, 2008 | 07:42 AM

sxr6

Pro

Joined: Nov 2004

Posts: 575

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From: Nice Lake Ontario

Bangkok: if the car was vapour locking, it wouldn't start again, trust me I know

LT1-350: have you tried the simplest solution first, adjust you idle speed?

Jun 25, 2008 | 11:36 AM

Bangkok Dean

Le Mans Master

Joined: Jan 2004

Posts: 8,295

Likes: 30

From: one night in Bangkok you are never lonely

Quote:

Originally Posted by sxr6

Bangkok: if the car was vapour locking, it wouldn't start again, trust me I know

LT1-350: have you tried the simplest solution first, adjust you idle speed?

In my experience the vapor lock can be in the fuel line along with the carb and will restart when pumping cool gas back up threw the fuel lines. My comments were not a guess but from months of looking for the problem and finally fixing it. Now if his choke is staying closed his idle will be higher as it will not kick down. I have had that happen forgetting to close the hand choke it idled high but ran supper rich.

The OP says the problem on hot days is at stopping so I assume his idle is OK when moving. Been there done that.

Jun 25, 2008 | 11:55 AM

Matt Gruber

Race Director

Joined: Oct 2000

Posts: 14,954

Likes: 79

From: central FL, near the beach.

Quote:

Originally Posted by lt1350

i didn't see any hot in there.
posters are notorious for poorly describing things, however

Jun 25, 2008 | 12:15 PM

Bangkok Dean

Le Mans Master

Joined: Jan 2004

Posts: 8,295

Likes: 30

From: one night in Bangkok you are never lonely

Quote:

Originally Posted by Matt Gruber

i didn't see any hot in there.
posters are notorious for poorly describing things, however

I hear you but in my case the engine never went over 190*
In any case I hope he is able to find his problem and not take months like it took me.

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Jun 25, 2008 | 02:06 PM

sxr6

Pro

Joined: Nov 2004

Posts: 575

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From: Nice Lake Ontario

Quote:

Originally Posted by Bangkok Dean

The OP says the problem on hot days is at stopping so I assume his idle is OK when moving. Been there done that.

Not saying your wrong but my experience is a vapour lock & your car won't star!

If car is moving I sincerely doubt it's idleing

He said "won't idle when warm", I assume he meant when warmed up & choke kicked off.

Jun 25, 2008 | 03:20 PM

#10

lars

Tech Contributor

Joined: Aug 1999

Posts: 14,356

Likes: 6,328

From: At my Bar drinking and wrenching in Lafayette Colorado

If idle quality is bad or erratic on a hot Holley, check for a warped metering block. A non-flat block will allow fuel crossover between idle and main circuit metering passages, and will cause the problems you describe. Just lay a straight edge across the block after you remove it from the carb and verify that it is flat within .005" in every direction and on both sides. If it's warped, just get a new one from Holley - a very affordable fix that will make a huge difference in idle quality.
Lars

Jun 25, 2008 | 08:46 PM

#11

my 76 ray

Melting Slicks

Joined: Mar 2007

Posts: 2,520

Likes: 11

From: Hinckley OH

It could also be a vacuum leak.

Jun 25, 2008 | 11:09 PM

#12

lt1350

Thread Starter

Cruising

Joined: Dec 2007

Posts: 12

Likes: 0

From: Maryland

To clairfy: Engine won't idle when it has warmed up. Choke - as it should - gradually opens as engine warms. The engine will continue to idle when warm until the first time I rev it. After I rev the engine - and the choke kicks off - the engine won't idle.
The car will restart after cutting out - but only if I keep my foot on the gas giving it some revs (it will idle at 700 to 750 - maybe as low as 650 while giving it gas). When I stop giving it revs it konks back out.

I will definitly check level of metering block. If level I will clean it.

thanks to all - this is a really big help