400 Engine Problem
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Junior User
Joined: Mar 2005
Posts: 93
Likes: 0
From: Jacksonville, AR
400 Engine Problem
hey guys ive got a 77 ford f-150 4x4 with a 400 and a np 435 tranny its been a solid truck since ive had it but the motor has always seemed to be a problem ive done a few things recently such as a new intake manifold headers and a new carb as well and it runs a little better but still seems sluggish what might cause the motor to be sluggish? after the engine warms up its not so noticeable but when i first start it in the mornings it idle's real low to like 2-300 and makes kindve a chugging sound when im driving it. its stalled out a couple times and i checked the choke and its working fine
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
Sluggish:
Ignition timing?
Vacuum advance?
Low compression?
Low idle/stalling:
Idle speed adjustment?
Carb idle mixture?
Stuck EGR valve?
Stuck choke?
Both:
Spark plug wires connected improperly?
Carb jets incorrect?
Vacuum leak?
Ignition timing?
Vacuum advance?
Low compression?
Low idle/stalling:
Idle speed adjustment?
Carb idle mixture?
Stuck EGR valve?
Stuck choke?
Both:
Spark plug wires connected improperly?
Carb jets incorrect?
Vacuum leak?
Thread Starter
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Junior User
Joined: Mar 2005
Posts: 93
Likes: 0
From: Jacksonville, AR
alright again this morning it stalled out on me and as i went to turn it back on i gave it some gas and it just sounded like it didnt wanna take it. it started up again but it just seemed like giving it gas wasnt helping much
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
'Giving it gas' means opening the throttle. Opening the throttle only supplies fuel to the motor if there is air flow through the Venturi.
A low manifold vacuum will produce this result. Check your manifold vacuum. A cheap vacuum gauge will do the job.
Retarded Ignition timing, a vacuum leak, and sloppy timing chain are some of the things that will cause low manifold vacuum. Start by checking the ignition timing.
Cargo Master
Joined: Dec 2004
Posts: 2,232
Likes: 3
From: NE Texas
My advice would be that you do NOT just start throwing parts at it. Start the troubleshooting process with a compression test. Look at the plugs while they're out and look for a lean or rich condition. If all cylinders are within 10% of each other, then connect the vacuum gauge and see what that looks like.
As one poster commented, please give us a better description of what you mean by sluggish.
As one poster commented, please give us a better description of what you mean by sluggish.
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Junior User
Joined: Mar 2005
Posts: 93
Likes: 0
From: Jacksonville, AR
ok i did a compression check on the engine i dont know what the range is for the 400 but here are the numbers
Left Rear - 145 Psi Right Rear - 140 Psi
Left Mid-Rear - 130 Psi Right Mid-Rear - 135 Psi
Left Front Mid-Front - 130 Psi Right Mid-Front - 140 Psi
Left Front - 135 Psi Right Front - 135 Psi
also the left rear and left mid rear plugs had oil on them
Left Rear - 145 Psi Right Rear - 140 Psi
Left Mid-Rear - 130 Psi Right Mid-Rear - 135 Psi
Left Front Mid-Front - 130 Psi Right Mid-Front - 140 Psi
Left Front - 135 Psi Right Front - 135 Psi
also the left rear and left mid rear plugs had oil on them
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Laughing Gas
Joined: Jul 2002
Posts: 843
Likes: 1
From: USA
That is fairly well balanced compression across the engine. Obtain a vacuum gage and hook is up to your "tree" fitting on the back of the intake manifold. Your altitude is only about 45 feet above sea level so you should have 20 to 21 inches of mercury at idle. If not then start looking for leaks. By disconnecting all the lines from the manifold and blocking them off it will tell you whether or not you have a gasket leaking. If you have a coffee can canister mounted beside the battery check it out. They are notorious for rusting out along the bottom. Just disconnecting a line and plugging the fitting with your finger can help in the isolation process.
Laughing Gas
Joined: Jan 2006
Posts: 883
Likes: 7
From: New-brunswick,Canada
compression is not the problem here. The oil on the plugs is not a good sign. Bad oil ring or from the sceal on the valves but it will not cause that. You did the compression test now do the vacuum test, i'm pretty sure you have a leak somewhere. Listen to gary...
Posting Guru
Joined: Jul 2007
Posts: 1,355
Likes: 1
i think he is having the samething as i am, my engine was just built.. i have the 4th cylinder plug with oil, and it started also when i changed the intake etc.... a bad ring wouldnt cause oil to be noticable in a plug, a seal could be or my guess a bad sealing intake... im going crazy with this...
Thread Starter
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Junior User
Joined: Mar 2005
Posts: 93
Likes: 0
From: Jacksonville, AR
ok i did the vacuum test at idle and it was at about 15-16 in. and im living in jacksonville, AR atm and the sea level is 275 ft not sure what it should be at. also the only vacuum lines i have connected atm is the brake booster and the vacuum advance everything else is capped off
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Junior User
Joined: Mar 2005
Posts: 93
Likes: 0
From: Jacksonville, AR
correction its at around 18 in. also i noticed when i had the hood up i heard a light knocking sound coming from the left side of the engine (same side that i found oil on the plugs)
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Junior User
Joined: Mar 2005
Posts: 93
Likes: 0
From: Jacksonville, AR
the previous owner i believe put advanced timing in the truck so when i tried adjusting the timing awhile back it was not right so we advanced it some to compensate for advanced gears and it sounds fine but i may be wrong what do you suggest?