79 400m runing right issues
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From: belton mo
79 400m runing right issues
Ok i just cant seem to get it right... it runs decent in park or neutral and idle really rough in drive reverse or any of the gears.. ive changed the transmission A/T modulator, tried another carb that is know good, new plugs,wires,cap rotor, checked firing order, over and over, reset timing like 15 times, just cant figure it out... any ideas.? thanks 79 400m..
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From: Northern Illinois
Why would you change the vacuum modulator? That simply controls the shifting of the trans.
If your sure the timing is correct and all the plug wires go to the correct cylinder it is probably a fuel related issue. Have you checked the air/fuel mixture screws? Should be about 2-2 1/2 turns out. What kind of carb are you running?
If your sure the timing is correct and all the plug wires go to the correct cylinder it is probably a fuel related issue. Have you checked the air/fuel mixture screws? Should be about 2-2 1/2 turns out. What kind of carb are you running?
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From: belton mo
because it was a vaccum leak because i took the hose off and it poured out tranny fluid .. so i replaced it.
yea checked the screws even played with them some its the orignal carb.it is the 2150 i believe.. my next step was the fuel pump but it still gets fuel just when i press the gas it just dont feel like it accerlates very well... like stumbles.. never smoothes out.. almost no power..
yea checked the screws even played with them some its the orignal carb.it is the 2150 i believe.. my next step was the fuel pump but it still gets fuel just when i press the gas it just dont feel like it accerlates very well... like stumbles.. never smoothes out.. almost no power..
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From: belton mo
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From: Davison, Mi.
Neither clue is defintive that you don't have a vacuum leak.
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From: belton mo
this truck has been egr deleted in the past ran great then.. in a different truck.. so there is only 1 port on the intake the one in the back of the intake for the power booster , tranny, vac advance.. if i remember right that should be all of it.. all hoses ive replaced...
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From: Up Nort Minnesota
did you block off the egr unit with a plate or just unplug it?
like dude says above, you gotta spray around with the truck running to find a vac leak.
lotsa things can leak vac. like the trans module you mentioned, if the diaphram rips you got a vac leak, same goes for a choke pull off, a vac advance on your distributor, heck even power brake booster, egr diaphram... then there's gaskets like intake & carb gaskets.
someone mentioned idle mixture screws. My 400's & 351M's have always been oddly thirsty that way, seems like mine have liked closer to 7 turns!! not kidding.
like dude says above, you gotta spray around with the truck running to find a vac leak.
lotsa things can leak vac. like the trans module you mentioned, if the diaphram rips you got a vac leak, same goes for a choke pull off, a vac advance on your distributor, heck even power brake booster, egr diaphram... then there's gaskets like intake & carb gaskets.
someone mentioned idle mixture screws. My 400's & 351M's have always been oddly thirsty that way, seems like mine have liked closer to 7 turns!! not kidding.
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From: belton mo
i didnt do the egr but the egr is not there anymore.. the guy b4 me put shorter studs on the intake.. ive been messing around with the truck for about 2 weeks now....
trans module is new. choke pull off?.. vac advance is ok cause the idle changes when i pull the hose off and put on.. the gaskets should be fine .. the only thing could be the power booster but the truck still stops.. so..
the next step is the fuel system.. only thing i havnt messed with is the fuel pump.
trans module is new. choke pull off?.. vac advance is ok cause the idle changes when i pull the hose off and put on.. the gaskets should be fine .. the only thing could be the power booster but the truck still stops.. so..
the next step is the fuel system.. only thing i havnt messed with is the fuel pump.
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From: Up Nort Minnesota
have you got vac lines routed to the thermostatic switches like one in the thermostat neck (radiator hose neck) ? that can make for a tricky vac leak cause it will be dependant on engine temp.
I've seen fords & other cars/trucks that have a bunch of vac hoses pulled off (deleted if you prefer) and they seem to not understand that if some of the vac ports on those thermo switches are left open but vac is plugged into one of them you will end up with a vac leak at either cold temp or warm temp, depending on where you are plugged into.
i'm not saying you've got a vac leak, just saying I've seen that before.
I'd also think about a spacer plate to get that carb spaced up a little since the egr is completely gone.
I've seen fords & other cars/trucks that have a bunch of vac hoses pulled off (deleted if you prefer) and they seem to not understand that if some of the vac ports on those thermo switches are left open but vac is plugged into one of them you will end up with a vac leak at either cold temp or warm temp, depending on where you are plugged into.
i'm not saying you've got a vac leak, just saying I've seen that before.
I'd also think about a spacer plate to get that carb spaced up a little since the egr is completely gone.
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From: belton mo
yea no i really just need someone to through ideas around with lol... the friend dont really know very much...
but those ports on the thersmat housing.. are off and blocked off with brass fittings
ive had another truck without a spacer like this one and it ran ok.. but yea one day itll get a 4bbl intake and carb.
but those ports on the thersmat housing.. are off and blocked off with brass fittings
ive had another truck without a spacer like this one and it ran ok.. but yea one day itll get a 4bbl intake and carb.
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From: Southern NM
Have you tried a test vacuum gauge to see what the actual reading is?The gauge is also a good indicator of potential problems in the engine.It is also a great tool to be making carb adjustments with.Should be a technical write up in the search feature of this site.Post some results and let us know how we can help.