idle prob

[stinger]

85 351 4bl carb i cant get it to idle until warmed up . was having prob with original carb put on a new holley truck avenger and same problems. stalls when warmed up and step on the gas .even dies on fast idle when cold any ideas of what to check

 

[Justshootme84]

Do you have an electrical choke??? Make sure your getting power to the carb, or watch to see if it opens up.

 

[highboy73]

how does it run warmed up?or going down the road?does it idle real high only?

you might have a vac leak.

I know a way to check for vac leaks that anyone can do but you have to be careful cause carb cleaner is flammible:start up your truck put the hose on a can of carb clean and very tediously spray around the carb and intake if the motor revs and smooths out at any time there's your leak.please be careful.

check your choke like he said 2 carbs same prob it's problly not the carb.

to set your floats start it up let it run shut it off and take out the big ***** on the side of the float bowl gas should just fill the threads,if not turn the ***** on top out for more or in for less.

is your timing on?not by ear either,i don't care what people say about timing by ear it only works sometimes,unless you know your truck and what your doing.

I know a little about the holley's and so does seabronc so if you run into some probs just ask.I also left a link in how to's holley lovers check it out and get to know your carb they are great once they are right

good luck

 

[Seabronc]

The first thing I'd like to ask is about your vacuum system. What has been disabled? Then is the exhaust and intake heat control still hooked up? what about the air intake cold wather system? If electric choke, have you tried adjusting it? Have you checked for vacuum leaks? Have you timed the engine according to the Emissions control sticker? Have you done the cold idle adjustment according to the emissions sticker? Have you adjusted the curb idle according to the emissions sticker? What's the CFM of the Truck Evenger? If it's larger than 650 CFM then it is too big for a stock 351W. You actually get poorer performance out of an oversized carb because the secondaries won't function properly especially if they are vacuum secondaries. Also the engine can only **** in fuel and air at a given rate depending on displacement.

The reason for all but the last question is simple, All of that is necessary for a good start and run engine. Vacuum leaks will make it impossible to adjust and keep it that way. The carb bolts needs to be torqued properly, (5 - 10 in. lbs), in order to make sure there are no vacuum leaks at the base. Do not over torque or you may crack the base. In winter the air intake needs prewarmed air from the heat shroud over the right side manafold. The intake and exhaust heat control valves need to be operating to recirculate exhaust into the intake manafold when the engine is cold. You should be able to see the control valves pull in and then release as the engine starts to warm up, if not then something in that system is bad. The choke needs to be adjusted to pull off at the right time and temp, (usually you will need to adjust a new one to delay pull off). What do I need to say about idle adjustment other than the cold needs to be high enough to keeep it running until the engins warms up and the curb idle needs to be adjusted so the engine will stay running when it is hot and in gear. The idle adjustments depend on the timing being right.

My 85 351W sticker, for example only. It may not be exactly what you need for your truck.

Good luck,

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[stinger]

carb has power to the choke. havent check for vacum leaks was running perfect and i was working 7 days a week for 3 months and it sat . then i had the problems. timing when set to the tag . failed emissions on a fresh rebuilt engine in AZ . had to ****** the timing to pass emissions and it ran okay little lacking on power but i never put it back up where it belongs after moving from AZ to TN . the truck advenger holley is the small cfm carb which i believe is 650 cfm. all of the emissions and vaccum are hooked up except for the bowl vents to the carbon canister and the preheater. once warmed up idles fine at curb idle but when i step on the gas it stalls unless i push the idle up to about 1000 rpm in gear, which makes 4X4 low speed use and nightmare of rideing the brakes. could a cracked fuel line back at the gas tank cause this wierd running also?

 

[Justshootme84]

I believe the HLY Truck Avenger is 670cfm, so it's not too much carb. Your problem seems to be fuel delivery, timing or vacuum related. Fuel delivery you can check visually if fuel is flowing into the carb or fuel line. Timing can be checjed and re-checked, should be 10-12 degress. Vacuum leaks are harder to trace, but alot of the emissions can be bypassed and the vital vacuum pressure-checked. I initially had alot of problems setting my Holley carb, but they wetre mostly due to the electric choke not working. You can always force the choke open to see if that's the cause. If I had to guess, I would suspect a vacuum leak somewhere. Check the ported vacuum fittings, or get a gauge and check it that way. Improper timing can affect the vacuum as well. Post your reswults and we'll get you up and running!!!

 

[Seabronc]

OK, I guess I didn't understand the problem. As far as the choke goes, my Holley did a similar thing due to pulling off too soon. I gradually increased the delay in pull off until it worked. My symptom was that it ran fine untill it started to warm up and then would want to stall when stopped at a light. I had to do the same thing you are doing (push it up to about 1000 RPM while holding the brake to keep it from stalling). Once warmed up it worked fine.

Another question about your carb. Did you hook the choke to 12V instead of the Ford tap off the alternator Stator. The Ford tap is about 7V and Holley instructions usually tell you not to use it. You need to pick off a line that only has 12v when the truck is in run.

If you just purchased the carb, I believe that you are entitled to free assistace from Holley.

Good Luck,

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[stinger]

well i found a cracked vaccum line beside the carb. had to wait for the motor to warm up before it would stay running to check things out. fixed the leak. noticed about a 200rpm increase when i sprayed around the base of the carb so i guess i need to replace the gaskets there again. very little hesitation now when i step on the gas. well now i have to let it cool all down again and see if it will stay running on the cold idle ,but that cracked line was on heck of a leak.

 

[Seabronc]

Since you discovered a vacuum leak at the bottom of the carb, I would look at the condition of the top of the intake manafold where the carb sets. Mine had a leak there that was caused by erosion from EGR gasses. I had to mill it down to get the surface flat again using a large flat grind stone. I could have taken it to a shop, but a little elbow grease works. It didn't look like much, but That gasket wasn't thick enough to make up for the erosion and a slight fall off to to the corner.

It wouldn't hurt to take a stone to check the flatness of the manafold at that point even if you don't see any erosion evidence. Just rub it arould a couple of passes and see if the scratch marks are even across it. If it's not almost perfectly flat, the carb won't seat on it properly and you could also crack the base of the carb while torquing it over a curved surface.

Good luck,

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[Seabronc]

PS, I also milled down the surfaces of the EGR spacer also.

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