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Davo
Davo, Master technician
Category: Car
Satisfied Customers: 3253
Experience:  ASE Master Technician/Advanced Automotive Diagnostic Technician
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94 CADILLAC STS: INJECTOR PULSE..vacume..MANIFOLD COVER THAT..BOOST

Customer Question

I HAVE A 94 CADILLAC STS WITH PO46 CODE I REPLACED BOTH O2S PUT STILL THERE CAR RUNS LIKE CRAP.REAR INJECTOR PULSE IS ABOUT 2.7 WERE FROUNT IS 3.4 AT IDOL.IF UNPLUG REAR 02 PULSE GOES EVEN AND CAR RUNS MUCH MUCH BETTER THEN CODE PO13 COMES UP BECAUSE REAR IS UNPLUGED.I KEEP GETTING BAD INFO FROM PEOPLE.ONE MAN TOLD ME THAT THE FPR SHOULD HAVE A VACUME LINE ON IT ITS UNDER THE MANIFOLD COVER THAT IS SEALED SO IT WILL HAVE VACUME.THATS WERE THE BRAKE BOOST GAETS ITS FROM. CAN SOME ONE THAT KNOWS WHAT THERE TALKING ABOUT HELP ME?COULD THIS BE A FPR GONE BAD?
Submitted: 6 years ago.
Category: Car
Expert:  Davo replied 6 years ago.
What are the O2 sensor voltages with the engine warmed up and ran at 2000 rpm for two minutes?Check at 2000 and at idle.
Customer: replied 6 years ago.
the voltages both bunce from .30 to .80 or so they are working the way they should be
Customer: replied 6 years ago.
the voltages both bunce from .30 to .80 or so they are working the way they should be .i have all so looked at the egr changed injectors checked compression and fuel pressure map and tps.keep in mind this 4.6 the cover of the intake is not just for looks.there is vacuum in it.
Expert:  Davo replied 6 years ago.
Then it would be time to pull the fuel pressure regulator out and see if gas is in the vacuum nipple.
Davo, Master technician
Category: Car
Satisfied Customers: 3253
Experience: ASE Master Technician/Advanced Automotive Diagnostic Technician
Davo and 4 other Car Specialists are ready to help you
Customer: replied 6 years ago.
i have already changed the fpr.please keep in mind i am a little better than a backyard tech.could this be a manifold or computer problem. because i have even gone through the wiring.
Customer: replied 6 years ago.
I DO NOT MEAN TO SOUND LIKE AN ASS BUT I HAVE SPOKE TO ALOT OF TECHS AND THEY SAY THE SAME STUFF.FOR SOME REASON SOME OF WHAT I HAVE ALREADY CHECKED WAS NOT POSTED.HERE WE GO.EGR,COMPRESSION,INJECTORS,AIR INTAKE TEMP SENS.FUEL PRESSURE, MAP,FPR,O2S,WIRING,TPS.I HOPE I DID NOT MISS ANYTHING.I NEED YOU TO THINK OUT SIDE THE BOX.THANK YOU.SORRY FOR SOUNDING LIKE A DICK.I AM JUST LOSSING MY MIND.
Expert:  Davo replied 6 years ago.
Start the engine and spray carb cleaner around the intake area and see if there is any rpm change noted.You may have a vacuum leak somewhere.I would also drop the converter and try again maybe it is starting to plug up.
Customer: replied 6 years ago.
I HAD TO PUT A STARTER IN IT.AND SAW THAT THE BACK TWO INTAKE BOLTS WERE NOT TIGHT.SO WHEN I WAS DONE THE CAR RAN BETTER BUT THE REAR INJECTORS ARE NOT PULSEING AS LONG AS THE FRONT STILL. DO YOU THINK THE CAT COULD CAUSE SUCH A LOPSIDED EFFECT? 3.5 FRONT 2.8 REAR IS ABOUT WHAT IS GOING ON.THE CAT IS CLOSER TO THAT 02 MAY BE THE HEAT IS CAUSING A DIFFERANCE SORRY FOR MY POOR SPELLING.AND YES I DID USE NEW GASKETS.
Expert:  Davo replied 6 years ago.
To be honest with you with the amount of time it has been running bad and the times you had the O2 sensor disconnected it may not hurt to simply change the oil at this point.Assuming the bolts were letting vacuum leak.It may not hurt to disconnect the battery to put the fuel trim back to the base starting point.
Customer: replied 6 years ago.
THE O2S WERE NOT UNPLUGED FOR ANY LONG PERIOD OF TIME I HAVE CHANGED THE OIL AND RESET THE FUEL TRIM BOTH BY DISCONECTING THE BAT AND GOING INTO OVERRIDE .I AM GOING TO DROP THE CAT AND RUN THE CAR AND SEE WHAT HAPPENS.DO YOU NEED ANOTHER 15 DOLLARS?
Expert:  Davo replied 6 years ago.
No were good.
Customer: replied 6 years ago.
I DROPPED THE CAT IT DID NOT MAKE A DIFFERENCE.I DONT KNOW WHY I DID NOT THINK OF THIS BUT I KNEW THE ALT. IS BAD BECAUSE THE LIGHTS PULSE AND VOLTS ARE LOW AT TIMES MORE SO WHEN THERE IS A LOAD ON IT.AS YOU MAY KNOW CHARGING PROBLEMS CAN CAUSE ALOT OF CRAZY THINGS TO HAPPEN.MY ELDO WOULD FEEL LIKE THE TRANNY WAS COMING OUT OF GEAR AT 65 BECAUSE IT WAS OVER CHARGING BUY ONE VOLT. WHAT DO YOU THINK.THANKS FOR YOUR HELP.
Expert:  Davo replied 6 years ago.
When I suspect an alyernator of causing problems I don't just check charging system voltage.I also check for a/c voltage being present in the system.If it goes above 300 millivolts (less can be a problem) you can bet digital circuits will be affected.Computers use digital signals and so do digital dashes.I would check for a/c voltage.
Customer: replied 6 years ago.
ME AGAIN THE PAIN IN ASS.I PUT ALT IN VOLTS UP AT 14.1. HERES THE THING AS IT RUNS THE VOLTS START TO DROP AS IT GETS HOT. I NOTICED A CUT IN WIRE A GOOD SIZE ONR THIS IS THE BAT WIRE AT BACK OF ALT.I THINK THE COPPER MAY TRURNING BLACK IN SIDE .THE NO BAT CHARGE DIS PLAY CAME ON THEN WENT OUT AS THE VOLTAGE DROPPED.THAT NEVER HAPPEN BEFORE BUT THE CAR NEVER CHARGED AT 14.1 .THE LIGHTS DO NOT PULSE ANY MORE.I RAN INTO A PROBLEM LIKE THIS BE FOR IN A CADDY WERE THE BAT WOULD START THE CAR BUT THE VOLTS WERE ALL MESSED UP.IT LOOKED LIKE A BAD ALT. BUT IT WAS THE BAT.WHEN CAR WOULD RUN NOT GOOD EITHER THE BAT LIGHT WOULD COME ON THE BAT WAS SHORTER BECAUSE IT WAS OVER CHARGED WITH BAT CHARGER AND YOU COULD SMELL IT. I GOUGHT A FAINT SMELL FROM IT WHEN THE BAT DISPLAY SAID NO CHARGE.I THINK THE SAME THING IS HAPPENING HERE.THE OLD ALT WAS BAD THE MOST THAT CAME OUT OF IT WITH NOTHING ON WAS 13.2.HAVE NEW BAT WILL PUT IT IN TODAY.BY THE WAY REAR INJECTORS ARE STILL PULSEING SHORT OR LEAN AS SOON AS IT GOES INTO CLOSE LOOP.
Expert:  Davo replied 6 years ago.
Why don't you run a new wire from the alternator to the battery?What Im not getting on this injector problem is how the rear are different than the front.Either the front is lean or the rear is rich.Maybe the injectors themselves are dirty.Have you ran a full strength injector cleaner in the car?
Customer: replied 6 years ago.
YES I WILL RUN NEW WIRE.ALREADY RAN CLEANER FOR 45 MIN.THE TIME SPAN THAT THE INJECTORS RUN.THE REAR AND FRONT RUN AT SAME TIME WHEN MOTOR IS COLD.FOR EXAMPLE AT 1100 RPMS COLD 4.4 FRONT AND REAR.MILLIE SEC.AS SOON AS CAR GOES IN TO CLOSE LOOP AT 675 RPMS FRONT 3.5 REAR 2.8 REAR IS NOW RUNNING LEAN. I TOOK ALL FOUR INJECTORS FROM FRONT AND SWAPPED THEM WITH THE REAR SAME PROBLEM.NOW I AM GRASPING AT STRAWS. I AM NOT ONE TO JUST START CHANGING PARTS BUT THIS CAR IS FORCEING ME TO DO IT.I HAVE EVEN RAN NEW WIRES DIRECTLY TO REAR O2 TO COMP. I HAD TO CUT WIRE FROM COMP AND NEW POWER AND GROUND EVEN KNOW I ALREADY CHECKED WIRES FOR SHORTS AND RESISTENCE AND STUFF.I NEED A TALL TREE AND A SHORT ROPE. IS THERE ANY WAY A CRANK SENSE BECAUSE IT HAS A AND B COULD CAUSE THIS.IT ALMOST SEAMS LIKE MAY BE THE REA SPARK COULD BE WEEK AND O2 PICKING UP ON IT AND RUNNING IT LEAN TO COMPENSATE.
Expert:  Davo replied 6 years ago.
Have you tried adding propane to see if you can even the values out?Get a propane torch and remove the nozzle.Place a rubber hose on the end.Turn on the valve and add some propane to the air intake.Do the O2 sensors respond to the propane?
Customer: replied 6 years ago.
NO I HAVE NOT.WHAT WILL THIS TELL ME.WHAT SHOULD I EXPECT TO HAPPEN .ON A SIDE NOTE IF YOU ARE EVER TRYING TO FIND A SHORT ON IGN 1 FUSE ON CADDYS LOOK AT THE GEAR SELECTOR SWITCH ON TOP OF TRANNY.I HAVE READ A LOT PROBLEMS PEOPLE ARE HAVEING WITH NO GAS GAGE NO AUTO LIGHTS NO AIR BAG LIGHT OR CHECK LIGHT WHEN CRANKING AND RO61 AND 62 WITH BLOW FUSE IN IGN 1.THERE IS A    THIN PINK WIRE GOING TO SWITCH CUT IT AND SEE IF SHORT GOES AWAY OR YOU CAR PUT CAR IN GEAR THEN PUT FUSE IN IT SHOULD NOT POP UNTIL YOU PUT IT BACK IN PARK.THE PINK WIRE IS PART OF THAT CERCIT THAT LOCKS THE DOORS WHEN YOU PUT CAR IN DRIVE.I KNOW THIS SOULDS LIKE A CRAZZY QUESTION BUT THAT TRANNY SWITCH WOULD NOT BE CAUSING ME MY PROBLEM COULD IN .I HAVE SEEN STRANDER THINGS.
Expert:  Davo replied 6 years ago.
If it brings the rear O2 sensor up it will verify some type of vacuum leak or compression losss.I know you checked static compression but have you done a dynamic test?never heard of that have you?Don't feel bad most techs haven't either.You remove the valve core from the gauge hose install it on a cylinder and start the engine.Record the reading.Do the remaining cylinders.If you have a weak or set of weak valve springs you will know pretty quick because the cylinders will read low.Actaully all cylinders will read lower than a static compression test.Give it a shot and let me know the outcome.Thanks for the short heads up.Idon't see too many 1994 vehicles anymore around here they are rusted away.Pa is tough with rust due to salted winter roads.
Customer: replied 6 years ago.
if the compression was bad wouldn't the motor still run like shit with the rear o2 unpluged.once the rear 02 is unpluged and the injector pulse is equal to the front motor runs good.i will try the propane and let you know.THANKS AGAIN.
Expert:  Davo replied 6 years ago.
It probably would but who knows we have tried just about everything under the sun so far.Let me know what the propane does.
Customer: replied 6 years ago.
well i used propane i put it in at the front of the throttel plate.it did not change any thing did i put it in the right place or should have i used i vacuum line like the brake boost. what i really did was i took out the vent off the top of the air induction the 4 inch tube that goes to the air filter.and let the propane in to that witch is right in front of the butterfly or throttel plate.let me know if i did it wrong.thank you.
Customer: replied 6 years ago.
i also fed propane into a vacuum line nothing happened.i took the cover of the intake off again and could see small amounts of gas on the bottom under the tubs that are in there.the fpr is new and i checked the rails there not leaking.when i did a fuel pressure test i also let it sit to see if the pressure would drop it did not why is there gas inside the intake that can't be right.
Expert:  Davo replied 6 years ago.
That was the right place.Did the O2 sensors respond at all?
Customer: replied 6 years ago.
i did not see any change.
Customer: replied 6 years ago.
there is gas getting inside the intake.i checked the fuelrails,and seals the fpr is new .i blew it all out so i will run it then check it again.i am going to get rails and injectors when i get a chance if there is fuel in there again my guess there will be .
Expert:  Davo replied 6 years ago.
There has to be fuel getting in there if the O2's did not respond to the propane.The voltage should have went high like 800-900 millivolts.
Customer: replied 6 years ago.
I TOOK THE COVER OF THE INTAKE OFF AND REMOVED THE FUEL RAIL THEN I TOOK OFF THE FPR PLUGGED THE LINE AND PRESSERIZED THE LINE THERE WAS NO LEAK OF ANY KIND.WERE COULD THE FUEL BE COMING FROM.THIS SUCKS.I HAVE NEVER HAD A CAR GIVE ME THIS MUCH TROUBLE IF THIS CAR WAS NOT MINT I MEAN MINT I WOULD BURN IT.HA HA HA
Expert:  Davo replied 6 years ago.
Try disconnecting the hoses from the evap cannister.Plug them off and try it maybe the purge valve or cannister is bad.
Customer: replied 6 years ago.
i will try that thank you for all your help.
Customer: replied 6 years ago.
i took off the lines on the canister. on change.on of the injectors must be leaking on the outside not from the nozzel if thats possible.there does not seam tobe any other way for gas to be getting in the intake.if the rails and the fpr are good.
Expert:  Davo replied 6 years ago.
I have replaced alot more than a couple for external leakage.The only thing you can do possibly is swap the front and rear fuel injectors and see if the O2 problem switches to the front.It has been a long time since I have been in the intake on one of those.
Customer: replied 6 years ago.
when i discoverd the code 46 that was the second thing i did i took all the rears and put them in the front.i saw gas in there then but just thought it came from me when lifted the rails up alittle gas came from the fuel line i did not bleed it all out.but the last time i took it apart i made sure i got it all.i am going to take it apart again and pull the spark plug wires then crank it and see if i can find the leak.i will let you know.back to the drawing board.
Customer: replied 6 years ago.
i took the top of intake off and removed wires.then cranked in up a few times did not see any gas but its not that easy to see.i also took out each injector and 80 lbs of air in it to see if there was any air coming out of it anywhere nothing.i do not know if that even will tell me any thing.i replaced the gas line o ring to.and there was gas in the intake again.i would put a intake on it if i thought it would fix it 575.00 not including rails and injectors.what i do not understand is why the motor runs smooth until it goes into close loop.most motors with problems run like shit when there cold.not this one.thanks for the tips.i will keep trying.i hope i fix it before july because i plan on taking it to the pocono 500 i go every year for the last 11.
Expert:  Davo replied 6 years ago.
Did you pull the cannister hoses?Remove your gas cap and try it.Let me know.I wish I could see this car first hand.Nothing personal dude.Could you find it in your power to turn off the caps lock and edit your sentences.Im not mad but it would make it easier to read for me.I'm as redneck as you are.I kill deer,turkey,rabbits,pheasants and grouse.Grouse are my favorite though.Yummy as all get out.Before you ask 20,12.10 and yes some are 3 and 1/2 inch.The 12 and 10 are.love the kick when I hit a turkey.I have a 3 inch 12 as well.The 20 is the standard 2 3/4 inch but I like the bigger loads.Lol.
Customer: replied 6 years ago.
Yes I had the gas cap off when I removed the lines off the canister.Sorry about the typing I can not type .I use two fingers or spell for that matter.By the way I live in Boston.I am not a redneck but I sure act like on.I also made sure the return fuelline was not plugged.I hope that's better.Thank you.

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