Won't Idle - Please help.

toyman317 · 11-24-05, 05:44 AM

I am very frustrated trying to figure this one out. My 60 starts fine although in this cold weather runs rough till it is warmed up...about 20 minutes because of having a header with no heat riser kit and inop choke. I just received a Heat riser kit so I will be putting that on soon. Anyway, when the truck warms up, it runs great for a minute then all of a sudden, it won't idle/run below 1500 RPM. After it dies, it starts up easily but still won't idle. Let it cool down a little and it will start up/idle fine. When it is not able to idle, I can still drive it as long as the RPM is above 1500. Carb is a Holley Vacuum is almost 25 inches and engine is desmogged. The only thing I did prior to this happening was change the fuel filter. Could this be an electrical problem of some kind...kinda feels like it. I don't think it is coil or igniter because the same thing happens whether I use stock set up or the DUI. I am stumped. Any help would be much appreciated.

humper99 · 11-24-05, 07:36 AM

First problem is the Holley Carb. I've never had a Holley on any vehicle that didn't give me problems. Put the Aisin back on. Second problem is that your vaccum actually seem a little high if your checking it at a 650 rpm idle. Normal should be a rock steady 15-21 inches of vac @ 650 rpm.

You said the problem started after you changed the fuel filter which would lead me to think you've got an air bubble trapped somewhere. Sorry can't be more helpful but you don't have a normal configuration with the Holley setup.

chitown40 · 11-24-05, 08:43 AM

toyman, do you have any of the smog stuff still on it, like the EGR perhaps? I ask because I'm going through my FSM now and looking at all the smog systems that are temperature sensitive. First thoughts are bad vac leak in the EGR system, specifically areound the modulator, if still attatched. If your EGR valve was stuck open, assuming you still have one, it wouldn't idle at all or very rough. Are you using the stock air cleaner? I'm not familiar with the Holley steup so I can't give you any definitive answers to your questions. Also the HIC (Hot Idle Compensation) system is also temp sensitive and could be another source of a vac leak at hot idle.

Good luck and post up some more info.

Gumby · 11-24-05, 09:09 AM

Good call on the sticky EGR. Try wacking it with a hammer and restarting. Very common with 5.0L. Customer would come in with an idles-fine-until-I-drive-it,-then -no-idle-complaint. Wack the EGR with a hammer and it idles fine.

wheezy · 11-24-05, 01:48 PM

Quote:

Originally Posted by Gumby

Good call on the sticky EGR. Try wacking it with a hammer and restarting. Very common with 5.0L. Customer would come in with an idles-fine-until-I-drive-it,-then -no-idle-complaint. Wack the EGR with a hammer and it idles fine.

Hammers can fix anything, a good whack is a wonderful thing.

toyman317 · 11-24-05, 07:14 PM

Thanks for the help so far. I just got this truck a couple months ago. Hope to do a toys for tots run next weekend.

There is no EGR. That has all been removed. It is real basic. Not the stock air cleaner but it does receive warm air from the valve cover. Everything is set up right and all the approp. vac. ports have been capped. There is nothing electronic connected to the carb. The fuel canister is there and all the vacuum hoses are in place. I wonder about the little hose coming off the canister that turns a sharp right. It is pretty kinked...but no leak. The vacuum reading of 25 was at around 900 RPM. When read at 600, it is consistently in the 21 range. The air pocket may be an issue since this happened right after I repl. the filter. How does one purge an air pocket?

The Holley is suspect and I wonder if the header is causing too much heat and causing vapor lock. There is no carb insulator. One thing I thought was odd is when I adjust the idle mixture on it, I can turn both screws all the way in and it idles higher. I still turn the screws out 1.5 turns. I have a stock carb and air cleaner I plan to swap into it after I get it rebuilt and all the parts together for the swap. I have a carb insulator coming soon. Also trying to nail down how exactly to hook up the vacuum lines to both carb and A cleaner. I sure wish someone would come up with an easy to understand diagram or rendition of a desmogged system. I am not real good with schematics sometimes...especially when they don't tell you where the parts are located. Looking forward to more thoughts on this situation. Thanks again.

toyman317 · 11-26-05, 05:37 PM

Might there be any other ideas?

Gumby · 11-27-05, 01:18 PM

Does the Holley have a fuel return?

Might be that you're having a heat soak problem

It also sounds as if your float might be too high. It's easy to chack and adjust on a Holley. About all they are good for.

toyman317 · 11-27-05, 03:36 PM

No fuel return on either one of my Holleys. Don't think they are made that way. Is there a fuel return on a stock carb? I don't see one. Float is right in the middle of the opening. Does it sound like a carb problem? Is it possible this situation is being caused by not having a heat riser kit? Would that make for carb icing or something? Thanks for the thoughts. Any more?