Warm idle issue?

[BarnabyHooge]

Both times I've driven my truck over 100 miles, I've had a problem where it kills once I get into traffic.

Example: When I picked the truck up, I drove through the town I purchased it in with no problems. I then drove about 100 miles home, and as soon as I hit city traffic, the thing would cut out soon after coming to a stop. It would start up again right away no problem. If I put it into park right as I stopped, the idle would increase and stay running, but once I dropped it into drive it would kill.

Same thing happened yesterday. I drove a 100 miles round trip. First 20 minutes of city driving were fine. Not too long after I got off the freeway on my way back, the thing just would not stay running at a red light, stop sign, etc. unless I held the brake down with my left foot and lightly feathered the accelorator.

I've been told it may just be a curb idle issue, but I thought I'd get the experts here to weigh in.

The Carb is a Holley 4160 if it matters.

Thanks!

[prostreetC-10]

Have you messed with the carb at all? When you say it starts right up after dying, do you have to pump the throttle or just hit the key? It's either dying from loading up or leaning out. Does it have a choke? Motors like a rich mixture when they are cold and that same mixture is usually way too much when the motor is warm. If it's an electric choke, you need to check to make sure the choke is coming and staying off. Other thing it can be is if the fuel level is too high, you can get fuel to dribble out of the primary boosters, adding to the curb idle supply. Is it really cold when you get started? I'd first look at the choke and make sure it's not sticking. Once it's warm, if it starts dying you need to pull the air cleaner off and look down the primary barrels to see if they look really wet......then report back.

[BarnabyHooge]

I haven't messed with anything yet. I'm just learning all of this stuff and want to get as much input as possible before I start adjusting anything. After it dies, all I have to do is hit the key and it goes. It's got a manual choke, which in all honesty, I have no idea what to do with. Normally it's just off.

Questions:
1. I assume "loading up" just means that it's getting too much fuel for one reason or another. Correct?

2. When you say the fuel level is too high, I take that to mean I need to check the float level and make sure that it's at the bottom of the sight plug?

I'll get another chance tomorrow as we're heading out to the flea market a ways away. If it happens again I'll be sure to check the barrells as you mentioned.

Thanks for your help. I'm reading as much as I can but there is no substitute for experience.

[prostreetC-10]

The only problem with experience is that trying to help someone over the internet can be much harder than a ride along or being able to stand over the motor to hear/feel what's going on. Yes, loading up is usually too much or too rich of a fuel supply. Once again, a cold motor likes a nice rich supply where a warm motor does not. Have you tried bumping up the idle just a tad? Adjusted the idle needles once it's warm? How clean is the carb? Always a good idea to check the air bleeds on top of the main body to make sure no pooh has gotten into them and clogged them up.

Kinda shooting from the hip here on thee ole couch. When you have to put your foot on the brake and the gas to keep it running, does the motor feel like it's shaking a bit? That's usually a lean condition. Let us know what you come up with this weekend.

[cdowns]

i'd say the first place to start is with a full tuneup// change air and fuel filters , clean/change and gap the points, clean/change gap the plugs. a check of all vaccume hoses replacing any that are cracked or dryrotted. set the timing,also oil and filter change too

all this should be done b4 ever thinking of putting hands to a carb

[BarnabyHooge]

I'm planning on changing the plugs and fuel filters before I leave tomorrow, oil's going to have to wait for another day. I've never done points before so that'll have to wait as well, although I do think there is work to do on the distributor based on a few other things I've read. It's a Mallory so I hope the local Autozone or O'Reilly's has parts for them.

[mclairmo]

Sounds like idle speed is too low. My engines often are set at 1,000 rpm at a warm idle. Also, make sure that choke plate is all the way open when the engine is warm. You may want to consider adding an electric choke to the carb for about $40-$50 so you don't have to fuss with it. Choke plate should be closed when cold, open when warm. You may also want to add a heat shield under the float bowls to make sure that the carb is not getting too much heat from the intake that could turn your gasoline to vapor. I dont think this is your issue, though since you are able to start it up again right after it dies. Full tune-up is a also a good idea, plugs, wires, cap, rotor, filters, etc, if not already done.

[BarnabyHooge]

New Plugs and fuel filter this morning. Started great and the idle was a lot smother. Dead on at 800 RPM. Drove just over an hour and parked for almost 3 hours. After getting back on the road and driving about 45 miles or so, just like clock work, it kills when we hit some traffic right after a toll on the freeway. I was able to keep it going by lightly feathering the throttle with my left foot on the brake. As I was watching the water temp, it looked like once it got to about 185-190 when at a stand still is when the throttle would start acting weird. After about 20 minutes of that it got worse. All I would have to do was start braking and then it would just kill instantly. Frustrating. I checked the barrels as soon as I got home and they were bone dry.

[cdowns]

do you hear a whooshing noise when you remove the gascap after running it for awhile? if you do, you have a tank venting problem causing no gas flo you'd need to get a vented cascap

another tthing that can cause it is the lazymans rubber fuelline from the pump to the carb with it laying on hot manifold causeing vapor lock and sometimes a real good fire

[BarnabyHooge]

No whooshing or rubber fuel line around the carb...

[cdowns]

about the only thing else i could think of if you have headers and tha gasline is too close it can boil gas causeing vapor lock// if thats the case a temp fix is to wrap the gas line with aluminium foil as a heat shield// still i'd try taking off the cascap when it happens to see if that solves it

[BarnabyHooge]

I'll give it a go next time around, thanks for the input.

[BarnabyHooge]

Clarification: The fuel lines coming directly from the carb are hard pipe, but just off the front of the carb it goes to a soft line with an inline filter to the fuel pump.

Any chance the fuel pump is just getting a little wonky and just acts up when hot?

[mclairmo]

Not likely, fuel pump is not heat sensitive. However, gasoline is.

[68gmsee]

Fuel pumps are cheap. If in doubt replace it. I had a problem where mine was sucking in air and acting up similarly to what your truck is doing.

Be sure and check those points, though.

[don t. - 72gmc]

Im not an expert, nor a mechanic, in any sense of the word.

Im going to go against everyone here and say its a spark issue.
This sounds alot like what I went thru w/my 70 GMC. Ran 50-100 miles and its started bucking, but you could keep it running w/a light foot in neutral at a stop. In my case, the points dizzy bushings had end play, and caused the points to not open/close like they should. A skip white HEI dizzy and new plug wires fixed my ride.

HTH....Good luck...don t. .....

[68gmsee]

Not sure why you say you're going against every one else... Some of us have deduced that with the points issue...

[junkyardjohn]

TRY THIS... WHEN IT'S COLD, PUT IT IN DRIVE, HOLD THE BRAKES & EXCELERATE. IF IT STUMBLES OR BOGS LOOK INTO YOUR DISTRIBUTOR. SPARK OR TIMMING ISSUE. GM MOTORS LUV HEIs & I LUV EDELBROCK CARB.s. BOTH ARE VERY SIMPLE & VERY DEPENDABLE. ANOTHER QUICK THING TO CHECK IS IF YOU HAVE A FULL 12 VOLTS ON YOUR HOT LEAD GOING INTO YOUR DIST. ASSUMING YOU HAVE AN HEI. ALREADY. IF NOT.. PLAN ON GETTING ONE. THEY ARE CHEAPER THAN A DECENT SET OF PLUG WIRES. JOHN (& BUY A 3' STICK OF 3/8 BRAKE LINE & FIX THAT FUEL LINE)

[BarnabyHooge]

Still no luck. Happpen again last night after a little cruise in the city. I am getting an oil leak that may be originating out of the back of the intake manifold. Any chance this is also causing a vacuum leak that's messing with my idle?

A couple of other things.

1. I don't even have to feather the throttle to keep it going. The lightest touch on the accelarator keeps it running. No change in sound or RPMs, it just stays running.

2. It does have an HEI.

No time this weekend, but I think I'm going to run it around until it starts doing it, then bring it home for a through investigation while it's happening. I haven't been able to do that as of yet for a few different reasons, mostly because it's happened at night.

[pats69c10]

I had very similar problem with my holley 4777 on a 327 and replacing the power valve in the carb fixed my problem. When the power valve is bad, it is open constantly flooding the carb when idling. When you're on the gas, which is when the power valve is supposed to be open, the engine runs fine.

[grs]

I would just rebuild the carb. It probably needs it anyway. Also the pump if it is old.
It's only money. Spend it before you wife does. LOL

[BarnabyHooge]

I actually had a bit of an oil leak out of the rear of the intake gasket. Based on the fact that it only happens when the engine is hot for a period of time, then continues until it's totally cool, I reasoned that I could be getting a bit of a vacuum leak once the manifold expands after reaching a certain temp. I've replaced the gasket (PO used rubber seals) but have yet to be able to get the distributer back in correctly. If I can't do it after one last try tomorrow, it's going in.

Once this non-sense is over I'll take a serious look at rebuilding the carburator.