loss of power when driving

Is it really running rough/ smoking/ etc. while trying to accelerate? Investigate a Stopped up Catalytic Converter.--The Medic

I don't know if this matters, but, it runs at 4,000 rpms when the engine is cold. Once it gets warmed up, it drops to 2,500 rpms. Do you still think catalytic converter?
Thank you for your time, Barry Jackson

Any other observations? Does your Check Engine light work at start-up?....Is it/ Has it been on constantly?--The Medic

No, just loses power once it gets warmed up. Anything else besides the catalytic converter? Thanks Again, Barry Jackson

Attempting a solution for your problem. Trying to get you one soon, as to get you ridin' again. I did leave a message for another Expert to assist, If I cannot come up with a solution soon.---The Medic

Thank you so much! I appreciate all your help. ~ Barry Jackson

For your idle problem

NOTE: A change in idle speed occurred because of a problem elsewhere. Enter this procedure after eliminating the possible causes listed below:

Contamination within the throttle bore and/or idle speed control device.
Throttle sticking or binding.
Engine not reaching operating temperature.
Vacuum leaks (air intake, vacuum hoses, vacuum reservoirs, power brake booster, etc.)
VERIFY:

Transmission is in PARK (A/T) or NEUTRAL (M/T).
Parking brake is APPLIED (automatic brake release is DISCONNECTED where applicable).
Wheels blocked.
Cooling system is filled to proper level.
Engine is at operating temperature.
All accessories (heater, radio, lights, etc.) OFF.
Throttle lever is resting ON the throttle plate stop screw.
Ignition timing is set to specification.
Perform EEC-IV diagnostics and resolve any vehicle malfunctions that are indicated by service codes. (Ignore this step if sent here from an EEC-IV Pinpoint Test step).
Engine OFF, disconnect the negative (-) terminal of the battery for 5 minutes minimum, then reconnect it. NOTE: Memory to radio, phone, and other programmable accessories may be erased when the battery is disconnected.
Idle Speed Setting

PROCEDURES

With engine OFF install specified feeler gauge between throttle plate stop screw and throttle lever. Automatic transmission .030 inches, manual transmission .030 inches.
Unplug SPOUT line and verify that ignition timing is 10°+/- 2°BTDC.
Disconnect idle speed control-air bypass solenoid.
With transmission in NEUTRAL (M/T) or PARK (A/T):
Allow engine to idle for 2 minutes.

Check/adjust idle rpm: Turn the throttle plate stop screw to 780 +25 rpm automatic transmission, 730 +25 rpm manual transmission.
NOTE: If you must turn the throttle stop screw IN, turn engine OFF, make estimated adjustment. START engine and repeat Steps 4, 5, and 6 before continuing.

Remove feeler gauge from throttle plate stop screw and throttle lever pad.
Reconnect SPOUT line.
Turn engine off and reconnect idle speed control-air bypass solenoid, verify the throttle is not stuck in the bore and linkage not preventing throttle from closing.
START engine and stabilize for 2 minutes then goose engine and let it return to idle, lightly depress and release the accelerator. Let engine idle, if problem exists, see Diagnosis by Symptom (Diagnostic Routines.)
NOTE: A condition may occur where the engine rpm will oscillate. This can be caused by the throttle plates being open enough to allow purge flow. To verify this condition, disconnect the carbon canister purge line and plug it. If purge is present, the throttle plates must be closed until the purge flow induced idle oscillations stop.

On Automatic Overdrive Transmission (AOD) applications check TV pressure adjustment, See Automatic Transmissions

Won't accelerate over 25mph-check and test the Airflow meter/sensor and throttle position sensor also check he fuel pressure -

**** What vacuum modulator did you replace -is for the tranny?? Could very well be the transmission slipping

I have a 1988 f250 460 7.5l. My truck start to have problems on the highway trying to get up to speed it would all of a sudden make a bunch of noise some of it sounding like a plastic bag blowing in the wind then engine would calm down and be good then back to noise trying to accelerate. Pulled over looked couldn't tell got back on the highway and it was just all noise and not wanting to accelerate. Just slowly moved down the highway at about 20 mph and then it started bogging down then died while the throttled was still pushed and would not start back up just cranking and trying. After about 30 mins it started but only while holding gas. It smelled very bad of gas and was very loud. Got it home and now it will idle decently but when you try to accelerate to about 2000 rpms it bogs down and sometimes dies. Also when you leave it idle it will shake like crazy. It also will sometimes die once it warms up. We have replaced the distriptor cap and rotor. The coil. And tested the ignition module. We are completely stuck . please help

check fuel pressure with a gauge auto parts rent it. also check vacuum at intake if 15" or below at idle then suspect clogged exhaust. fuel pressure should be 30-45 psi with key ononly

1986 Ford F250 V8 Two Wheel Drive Automatic

I switched from mechanical fuel pump to electric Airtex E8012S, 5-9 psi, 30gph, new fuel filter, connected to 10amp fuse. I spliced into the 10amp fuse wire for the "aux fuel solenoid". Engine starts and idles fine. When i put the truck in gear and take off it spits sputters and gags and its a no go. It will idle in gear just fine.

Update: I called Airtex. The electric fuel pump manufacturer and discussed the problem. Turns out that the above fuel pump does not put out enough volume for a 460ci motor. Airtex suggested a E84070 pump. So went to O'Reilly's and got an Airtex #E84070 electric fuel pump. I will be installing it today.
Wish me luck!

Good luck!

I installed the recommended pump from Airtex. idled like crap. I re-adjusted the float level and tinkered with idle screw. Now it idles at least. Fuel pressure at the carb is almost 5psi. No leaks. Still no acceleration.
Bogs out when you rev the engine like its starving for fuel.
Help me out here guys, cuz i'm lost for causes and running out of money and patience. I have faith in you guys.

How did it run with the mechanical pump? If not good, your carb may need a new accelerator pump. This gives a shot of fuel for take off... Which carb is on it and I will see if I can locate a diagram...
Here are the specs and testing info for the fuel pump...mechanical, you electric should be set to deliver this pressure.
FUEL PUMP
NOTE: 5.0L MPFI models use electric fuel pumps and 5.8L 4-Bbl. models use
mechanical fuel pumps. On 7.5L 4-Bbl. models, the Hot Fuel Handling
application uses in-tank mounted electric fuel pumps. All other
applications use mechanical fuel pumps.
Mechanical Fuel Pump (Volume Test)
On 5.8L and 7.5L 4-Bbl. models, remove air cleaner. Slowly disconnect fuel line at filter. Using
a suitable container (one pint minimum), place at end of disconnected fuel line. With high
tension wire disconnected from coil, crank engine 10 seconds. If fuel flow is within
specification, proceed to pressure test. If not, proceed to next step.
1.
If fuel flow is low, repeat test using remote vented can of gasoline. Remove fuel pump inlet
hose. Connect a length of fuel line hose to fuel pump inlet and insert other end into remote can
of gasoline. If fuel flow is within specification, problem is plugged intake fuel filter or a kinked,
leaking or plugged fuel line or hose.
2.
Mechanical Fuel Pump (Pressure Test)
Remove air cleaner. Connect suitable pressure tester to end of fuel line. Start engine and let run for at
least thirty seconds. Read pressure and if not within specification, replace fuel pump. Reinstall air
cleaner.
Electric Fuel Pump
On 5.0L MPFI models, disconnect fuel return line at fuel rail. Connect hose to container. Connect
pressure gauge at diagnostic valve on fuel rail. Disconnect wiring connector at fuel tank and apply 12
volts to pump with jumper wire.
On 7.5L 4-Bbl. models, disconnect fuel line just before the vapor separator unit. Connect a hose from
fuel line to a suitable container. If fuel flow is not within specification, electrically check fuel pump.
If still not within specification, replace pump-sender assembly.
FUEL PUMP SPECIFICATIONS
Application Specification
Electric Fuel Pumps
5.0L MPFI
Pressure (1) 39 psi (2.7 kg/cm2 )
Volume (1) 1 pint (.5L) in 30 seconds
7.5L 4-Bbl.
Pressure (1) 4.3 psi (.30 kg/cm2 )
Volume (1) 1 pint (.5L) in 20 seconds
Mechanical Fuel Pumps
Pressure 6.0-8.0 psi (.42-.56 kg/cm2 )
TUNE-UP - V8 -1986 Ford Pickup F250 Page 1 of 2
http://www.ondemand5.com/mric/common/asp/printart.aspx 4/28/2010
Application Specification
Volume 1 pint (.5L) in 20 seconds
(1) Delivery capability averages.
© 2008 Mitchell Repair Information Co., LLC.
TUNE-UP - V8 -1986 Ford Pickup F250 Page 2 of 2
http://www.ondemand5.com/mric/common/asp/printart.aspx 4/28/2010

A big thank you Merlin for responding!

I have at normal idel 4.5 - 5 psi. at the carb. Starting cold 9 psi. at the carb. Fuel pump puts aout 72 gph. working fine no leaks.

I discovered yesterday that if i manually close the choke plate almost closed and push the throttle open, it will run like a lion with turpintine on it's rear!

So i'm kinda leaning towards a bad fuel accelerator pump?

What do you think?

That was my first thought, but it might also need a mixture adjustment, fully warm motor should have a fully open choke...how old is the choke thermostat?

I dont know about a choke "thermostat". The choke is electric. I just dont understand why i have to manually hold the choke plate at top of carb almost closed in order to get the engine to run at high speed. Pumping the throttle dosent keep it running unless i almost close the choke plate. Carb is getting enough fuel. Fuel pump puts out 72gph.
Acclelrator pump works. It's just getting enough fuel to keep running. I'm thinking there is an adjustment behind the electric choke. Like a little plastic thing with a tensioning spring. Wish i had a picture. Should be an adjustment for it.

My 87 F250 4X4 W/460 &C6 Trans Has a problem That is either a clogged fuel filter or in the ignition. Maybe in the brain box or distributor ect. It loses power on hills and pulling a trailer. Does MSG or other ? Make a stock replacement for the fords brain box located on the drivers side wheel well. And where are the fuel filters located on this truck? Frame rail? & carb inlet line? and between fuel pump & carb? are there 3 ? How can I get this rig to run smooth and strong? where do I start? Thanks Gail Ralls.206 818-0729 any time

Yes an aftermarket brain is available for this truck. Also, the fuel filter should be along the frame rail. Also, there is only one fuel filter.

Based on your discription, it sounds like the catylatic converter may be plugging. Have you checked it?

Any black smoke from the exhaust? Could be a vacuum leak or mixture adjustment. Is the carb a carter? holley? Post a photo if you can. Also check the mounting gasket and hold down nuts, if the base gasket is cracked or loose, you will NEVER get it adjusted right... Snug the nuts down evenly, but not excessively. Here's a few simple things to check, Float is important and can be adjusted on Holley carbs without taking it off or disassembling it... FLOAT LEVEL - WET 1. Start engine until it reaches normal operating temperature. Place vehicle on a flat surface. Remove air cleaner, if installed. Run engine at 1000 RPM for 30 seconds to stabilize fuel in carburetor. 2. Stop engine and remove sight plug from primary side fuel bowl. Check fuel level. Fuel level should be at bottom of sight plug hole. If fuel spills when plug is removed, lower fuel level by turning adjustment nut clockwise. 3. If fuel level is below sight plug hole, raise fuel level by turning adjustment nut counterclockwise. Turning adjustment nut 5/32" (4 mm) will change fuel level about 1/32" (.79 mm). 4. Tighten lock screw and install sight plug. Start and run engine at 1000 RPM for 30 seconds. Stop engine, remove sight plug and check fuel level. If necessary, adjust fuel level. 5. If fuel level is at bottom of sight plug, install sight plug using a new plug gasket. Repeat procedure for secondary fuel bowl. Secondary throttle MUST be used to stabilize fuel level in secondary fuel bowl. ACCELERATOR PUMP LEVER 1. Place throttle valves in wide open position. Using a feeler gauge, measure clearance between lever adjustment screw head and pump arm with pump arm manually depressed. See Fig. 3 . 2. To adjust, loosen adjustment screw lock nut. Turn adjustment screw in to increase clearance, and out to decrease clearance. Each 1/2 turn of adjustment screw equals .015" (.38 mm). Tighten lock nut. Fig. 3: Accelerator Pump Lever Adjustment NOTE: Each 1/2 turn of adjustment screw equals .015" (.38 mm). ACCELERATOR PUMP STROKE Accelerator pump stroke has been preset at factory. Setting should not be changed. If original setting has been changed, adjust as follows: Check that plastic accelerator pump cam is aligned with correct hole (top or bottom) in throttle lever. Plastic accelerator pump cam is located behind throttle lever. If not aligned with correct hole, remove screw. Reposition in correct hole. Install and tighten screw. SECONDARY THROTTLE VALVES Hold secondary throttle valves closed. Turn secondary throttle shaft stop screw out until secondary throttle valves seat in throttle bores. Turn screw in until it just contacts secondary throttle valve lever. Turn screw in an additional 3/8" (10 mm) turn. CHOKE PULL-DOWN 1. Place carburetor on a stand which will allow access to pull-down diaphragm vacuum passage on underside of throttle body. See Fig. 4 . Mark choke cap and choke housing for adjustment reference. 2. Using a hacksaw, carefully cut a slot in head of choke cap breakaway screws. Using a screwdriver, remove breakaway screws and conventional screw. Remove retainer, choke cap, and gasket. 3. Temporarily install choke cap and gasket. Line up marks made prior to disassembly and rotate cap 90 ° counterclockwise from this position. Secure choke cap with one screw. 4. With choke plate fully closed, actuate choke pull-down diaphragm by applying at least 17 in. Hg of vacuum. Using a drill or gauge, check clearance between lower edge of choke plate and air horn wall. 5. If adjustment is required, carefully remove diaphragm adjustment screw cap with a small punch or screwdriver. See Fig. 4 . Using a 5/16" Allen wrench, turn screw clockwise to decrease clearance and counterclockwise to increase clearance. 6. Maintain vacuum applied to diaphragm during adjustment. Cycle vacuum from 0 to 17 in. Hg to verify adjustment. When adjustment is correct, apply RTV sealant to adjustment screw cavity and check fast idle cam position. Fig. 4: Choke Pull-Down Adjustment FAST IDLE CAM POSITION 1. Using a hacksaw, carefully cut a slot in head of choke cap breakaway screws. Using a screwdriver, remove breakaway screws and conventional screw. Remove retainer, choke cap, and gasket. 2. Temporarily install choke cap and gasket. Line up marks made prior to disassembly and rotate cap 90 ° counterclockwise from this position. Secure choke cap with one screw. 3. Apply vacuum to choke pull-down diaphragm and cycle throttle. Fast idle speed screw should rest on top step of fast idle cam with throttle closed. See Fig. 5 . 4. If adjustment is required, turn adjustment screw clockwise to position fast idle screw higher on second step. Turn counterclockwise to position screw lower on second step. 5. Remove temporary choke cap and gasket. Install original locking gasket, choke cap, and retainer. Secure choke assembly with 2 breakaway screws and conventional screw. Fig. 5: Adjusting Fast Idle Cam Position CHOKE UNLOADER Hold throttle valves wide open. Apply light closing pressure on choke valve. See Fig. 5 . Measure choke unloader clearance between lower edge of choke valve and air horn wall. To adjust, bend pawl on fast idle cam lever.

Thank you for your response merlin. There are no vacume or fuel, vacume or smoke of any color from exhaust. The float level for primaries was checked and properly adjusted. Cold start; I depress the throttle one time which sets the choke, start the engine. It runs at fast idle. As the engine warms up, it slows to curb idle. Depress the throttle and it sounds like it ran out of fuel and will die. Let off the throttle and it will idle. It will restart and idle. I havnt checked accelerator pump measurements yet or the nylon fast idle cam behind the electric choke yet.And i dont think the electric choke is adjustable. Heres some pics of what i have. This is an 4180C holley/motorcraft carburetor and it takes an Renew kit #3-1346 from Holley.

Both floats are adjustable on these, I happen to like the mechanical pumps... my old fords had nothing but mechanical. If you have a small ball peen laying around, tap the carb in several spots with the engine running, this may dislodge a small bit of dirt in the carb, if any is in it. It looks fairly new? Rebuilts do not always perform well on the first try, I had a 66 Tbird that I put 5 rebuilts on in one day! If it is a rebuild, it may not have the right jets or metering rods for the application. Have you tried the mixture screws yet? All carbs need to be matched by adjusting the mixture, Use a tachometer and adjust idle as low as possible, then obtain the highest RPM reading on both screws, then rest idle speed. If it sounds like its out of gas it may be set way too lean!

Heya guys. new news. My carb is an 4180C (Calif emissions) Non adjustable choke and no idle mixture screws to mess with and im waiting for a carb rebuild kit from Holley. I'll update when i install it.

I'm still waiting for the carb rebuild kit from Holley. The carb is a 4180C for CA. emissions. The choke is electric non adjustable and there is no idle adjustment screws. I was thinking the power valve might be the root of the problem, even though there is no black smoke out the tailpipe. That's supposed to supply fuel per manifold vacuum after the primaries open.

All carbs have mixture screws even this one, to get at them you need to remove the plugs that cover them... they are on the base(throttle body) of the front of the carb under the fuel bowls.

Heya guys! I finally got my Renew Kit from Holley today. Ya the instructions suck. The print is so small i cant read it with my triple bifocal glasses. I'll attempt to rebuild the carb sometime this week hopefully. Been pretty busy lately but i'll try keep yall updated.

There is more to rebuilding these than puttin in the new parts... Carb rebuilders soak them in solvent for 4-6 hours while vibrating the parts...

hey guys! I got my Carb rebuild kit today and will be installing it sometime this week hopefully. I've been pretty busy lately. Holley Carb Renew kit 3-1346 for a 4180C carb.
As usual the instructions suck. The print is so small, I cant read the instructions with my tripple bifocal glasses. Holley could improve on this. more later

You have the cleaning tools? Shop air?

I drove it the other day about 10 miles, it wouldn't go over 55. Then drove about 2 miles, wouldn't go over 30. Then another mile or so and it wouldn't go over 15. Now it won't move at all. It's a stick. What could it be?

Is it a lack of power or a lack of motive force? If you put it in reverse, does it go anywhere?

Jack up and support the rear end. See if the driveshaft moves when it's in gear(forward or reverse). If not, we have a few possibilities.
First, the pressure plate could be bad.
Second, bad clutch disc.
Third, broken input shaft.
Fourth, broken output shaft.
Fifth, other internal transmission problems requiring overhaul or replacement.

the timing on my 86 f-250 4x4 with 5.8 litre engine is not kosher something is wrong with it when #1 is at top dead center on intake stroke the timing mark is 180 degrees out i have pulled the distributor out and reset but truck would not run also have moved wires 180 deg but still wont work could it have wrong harmonic balancer installed truck runs very sluggish and very slow revving up it also has automatic tranny and holley 4 barrel

check real close and make for positive you have the timing mark if i remember right some of those have 2-3 marks on it and it will throw you off.

[quote:d5bc663a94="jeftfields"]check real close and make for positive you have the timing mark if i remember right some of those have 2-3 marks on it and it will throw you off.[/quote:d5bc663a94]
you are correct it has 3 marks on it but none are anywhere close at TDC or 180 out i have timed a lot of vehicles but this one threw me off and i was wondering if there was a way to fix it without teardown

i think the only thing you could do at this point is to remove the #1 spark plug whitch is the first one on the pasenger side,have someone turn the motor over little bumps at a time,with your finger over the hole in#1 cyl,as you feal comp,stop then recheck for timing mark,and readjust dist, to #1,with this done you should get something out of the truck.