Community Forums

TXredfish · 11-05-2013, 05:34 PM

When I start my MH engine. It misses, sputters and dies unless I hold down the gas pedal until warmed up. The rpm goes up and down until warmed up. After warm up it purrs like a kitten and runs just fine. No misses or dying. I have cleaned the MAF sensor, changed fuel filter and air filter. About a year ago, I replaced the fuel pump, fuel filter, spark plugs and wires. No error codes or engine lights. It acts like it is starving for gas because of having to hold down gas peddle and hold at 1500 RPM. Any ideas .....................

lx22 · 11-05-2013, 05:58 PM

Vacuum leak!!!!

garyspang · 11-05-2013, 08:04 PM

The engine runs great when the electronic feedback loops are closed, but it runs lousy open loop. Check for anything that can let extra air into the intake manifold. Once the loops close, any small air leaks are compensated for and you will never verify that you have plugged up the leak. So don't let the engine warm up while you are troubleshooting.

TXredfish · 11-05-2013, 09:01 PM

Garyspang, I don't understand. Can you explain farther such as what to troubleshoot or what to check. Thanks ............

garyspang · 11-06-2013, 10:11 AM

It is to time consuming to give you minute details. The intake manifold at idle has a vacuum in it. Anything that lets air into it besides the throttle body, will upset the fuel to air ratio and the engine will idle lean and stall out. Running the engine faster swamps out this small unwanted air leak and the engine continues to run without computer control. Once the engine heats up the computer takes over and makes the injectors deliver more fuel. The computer can not tell the difference between a tiny air leak or a slight throttle movement. So everything seems normal after the engine heats up.
So look at everything that eventually is piped or hosed into the intake manifold and plug it up, one item at a time until it idles normal when cold. This is what the previous posting called looking for a "Vacuum Leak".
Find an experienced mechanic, make friends with him, maybe split a six pack or have coffee and dough nuts with him. Searching for a remedy is a potentially tedious process. The best to you.

TXredfish · 11-06-2013, 03:22 PM

Thanks Garyspang....................

spritz · 11-06-2013, 05:50 PM

Quote:

Originally Posted by garyspang

It is to time consuming to give you minute details. The intake manifold at idle has a vacuum in it. Anything that lets air into it besides the throttle body, will upset the fuel to air ratio and the engine will idle lean and stall out. Running the engine faster swamps out this small unwanted air leak and the engine continues to run without computer control. Once the engine heats up the computer takes over and makes the injectors deliver more fuel. The computer can not tell the difference between a tiny air leak or a slight throttle movement. So everything seems normal after the engine heats up.
So look at everything that eventually is piped or hosed into the intake manifold and plug it up, one item at a time until it idles normal when cold. This is what the previous posting called looking for a "Vacuum Leak".
Find an experienced mechanic, make friends with him, maybe split a six pack or have coffee and dough nuts with him. Searching for a remedy is a potentially tedious process. The best to you.

I could have wrote what the First OP stated.
Mine is a 82 Pace Arrow 454 4 BBL so no injectors not even sure if it has a computer(

). It started acting up just like the OP states, after we changed the plugs wires a week or so ago, ran great until the weather dropped out and highs in upper 30's under 30 @ night & am. If I hold the butterfly open on the 2 BBl side it works out of it and runs on high Idle and smooths out if I don't it looks like a Diesel (there is a black sootie aera on the grass by the exhaust pipe . I have always started it once to the floor, I think to set the choke,
turn the key and ran great.
My neighbor has been over a couple times and he always say something different.

Tonight he says its the choke pull off.

I am temped to just wait until we leave for TX next month. Any ideas? Tim

dieselclacker · 11-06-2013, 06:16 PM

I have to agree with your neighbor, choke pull off, or vacuum line that operates it. Choke pull off controls the air gap that the carb must have between the choke butterfly when the choke is on, and the carb inlet. No air, no run. Changing the plugs and wires should not have an effect on the choke pull off. Check to make sure there wasn't a vacuum line broken or knocked loose.

spritz · 11-06-2013, 06:42 PM

Quote:

Originally Posted by dieselclacker

I have to agree with your neighbor, choke pull off, or vacuum line that operates it. Choke pull off controls the air gap that the carb must have between the choke butterfly when the choke is on, and the carb inlet. No air, no run. Changing the plugs and wires should not have an effect on the choke pull off. Check to make sure there wasn't a vacuum line broken or knocked loose.

Thanks, he said that at first that there was a vacuum leak, then he said it is the choke pull off, maybe the same in its self.. I guess I will get one in the am he said they are around 20 bucks. Thank you