I INSTALLED REBUILT LONG BLOCK IN MY 94 FORD F150 SEVERAL YEARS BACK AND EVERY SINCE INSTALLED IT WILL USE I QT OF OIL ABOUT EVERY 1500 MILES AND THE MOST AGGRAVATING THING IS THAT WHEN I HAVE CRUISE CONTROL ENGAGED ANYTHING ABOVE 55 MILES PER HR. AND HAVE TO HIT BRAKES SUDDENLY IT WILL BACKFIRE IN THE EXHAUST SOUNDS LIKE ON RIGHT SIDE OF ENGINE IF TOUCH BRACKES GENTLY IT WILL NOT. HAVE FRIENDS THAT ARE MECHANICS AND WE HAVE TRIED TO FIND NO LUCK, I MECHANICED PROFESSIONALLY IN EARLY 80’S HAS STUMPED US ALL, ANY SUGGESTIONS?
The engine using oil every 1500 miles is nothing. Most new cars that use 1 qt every 1,000 miles is considered normal by the manufacturer.
The backfire while braking could be caused by a defective vacuum brake booster check valve or a leaking brake booster diaphram. When you step on the brakes you ask the engine vacuum to assist in the power brakes. If there’s a leak in this system you introduce extra air into the engine. This leans the fuel mixture out which causes the fuel to ignite at the wrong time which causes the backfire.
Tester
BRAND NEW BRAKE SYSTEM INCLUDING BOOSTER HOSES ALL COMPONETS RELATED TO BRAKES ONE OF FIST THINS SUSPECT
Then you might want to look at the Speed Contol Servo/Amplifier Assembly.
One of the inputs into this assembly is engine power.
Tester
changed this also had no affect
You’re killing me here.
You’re saying the engine backfires when using the cruise control, and stepping on the brakes hard?
Tester
ADDITIONAL PROBLEM THAT MIGHY HELP DIAGONOIS WHEN SHUT ENGINE THERE IS A POOT SHOUNDS LIKE TRUCK TRACTOR LETTING OFF AIR BRAKES
These engines should be equipped with distributors and TFI modules. You might consider whether or not the ignition timing is late as that can cause a backfire in the exhaust system.
When checking and adjusting the timing the SPOUT connector MUST be disconnected.
Your last statement is a bit fuzzy to me as I don’t understand the “shut engine” part. Does that mean when you shut the engine off or what?
IGNITION CONTROL MODULE REPLACED ALSO COMPUTER DISTRIBUTER AND ALL IGNITION COMPONENTS,INCLUDING WIRING I HAVE BEEN WORKING TRYING TO FIND FOR ABOUT 4 YEARS SINCE INSTALLED ENGINE AND PROBLEM STARTED. THE COMPRESSION RELEASE SOUND OCCURS WHEN I PULL UP AND SHUT THE ENGINE OFF IT SOUNDS LIKE AIR BRAKE RELEASE MAY OR MAY NOT BE ASSOCIATED WITH BACKFIRIG WHEN HIT BRAKES WITH CRUISE CONTROL ON.
Please stop using all caps.
Backfiring from the exhaust indicates the presence of unburned fuel in the exhaust system.
This could come from late timing or poor compression.
Have a helper shut the engine off while you listen under the hood for where the “poot” comes from.
Does the cruise control use engine vacuum?
THE OIL USAGE IS PERFECTLY NORMAL AND I SUSPECT THE BACKFIRE WHEN YOU APPLY THE BRAKES IS COMING FROM PROBLEMS WITH THE CHECK VALVE IN THE BRAKES BOOSTER SYSTEM. TRY PINCHING OFF THE HOSE THAT GOES TO THE BOOSTER AND SEE IF THAT AFFECTS THE PROBOLEM.
And please, turn off your caps lock.
Changing all of the ignition components still does not answer the question. Has the ignition timing been set in the manner in which it’s supposed to be?
The parts can’t just be thrown on and called good.
The air brake noise as you describe it may be a separate issue and related to the brake booster.
Exactly which engine are we discussing?
Never mind, the only engine that year was the 300 cu in inline 6. I’d suspect a defective valve lifter or improperly adjusted rocker arm. They are hydraulic lifters, but they use floating rockers and are adjustable.
Check the AIR pump plumbing and vacuum cntrols and all vacuum lines and components. A restriction in the vacuum to the MAP could be causing a rich mixture when the throttle is cut while keeping the AIR in the circuit, Excess fuel and air in the exhaust will often explode.
STOP YELLING
And the oil consumption is no problem.
already checked" pooting"is coming back thru intake tube for breathe,r the brake booster has been replaced along with tube and check valve.cruise does not have vaccumn. I have been hoping that I had missed something in all of my checking but my suspicion is that the machine shop in longview tx that built this long block messed up with their rebuild and goofed up with rings and valve grinding, letting compression and unburned gases bypass causing both problems. thanks for help