one thing then another
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From: bayside usa
one thing then another
91 F150 302 5SPD..HAD ENGINE LIGHT COME ON AND MOTOR STARTED TO IDLE BETWEEN 600 AND 900 RPM'S... DISCONNECTED THE BATTERY TO CLEAR THE COMPUTER...NOW IT IDLES AT 900 RPM AFTER STARTING AND STALLS OUT WHEN I COME TO A STOP AFTER DRIVING.. haveing the rolling idle went ahead and changed the iac sensor but it dident help..shows code 43 oxygen sensor...need to know if a bad oxygen sensor would cause the motor to idle up and down..it also seems like the motor is loading up (to much gas) noticed black smoke from exhaust when this happens so pulled some plugs and they were all black from fouling..again could the oxygen sensor be doing this??? tryed changing the oxy sensor with the proper sockey but it striped it and vice-grips are not working...anyone have any ideas.thanks
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Joined: Aug 2003
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From: CA
sounds like your on the right track, replacing sensor.if truck was running normal,gotta go with codes.(im not the expert on codes) you might try soaking with penetrating oil, tapping and putting some heat (torch)on the area around the sensor. good luck steve
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From: bayside usa
lets see...changed iac.. oxy sensor.. map sensor.. no luck motor still loads up..if this was a carbureted motor i would say the motor was flooding with gas...all i can think off now is fuel pump trouble or ignition trouble....if it helps when this hole thing started i remember being stoped and the motor just quit and started up with no trouble,,seems i dont know what im doing..any help PLEASE
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fyi the O2 sensor doesn't come in to play until the engine has finished it's warm up cycle. So any problems seen on initial start up are most likely not related to the 02. The code is telling you the computer is getting a reading from the 02 that it doesn't expect, that doesn't mean the 02 is bad, the trick is figuring why that system is not working properly.
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From: peoria, az
Well, I've been watching to see where this was going, not wanting to jump in out of line so, I think i'll put in my 2 cents now. Your O2 is seeing an overly rich condition which you do appear to have so it must be correct. You should probably check your fuel pressure as it may be too high indicating a bad regulator or a restricted return line. Check the vacuum source to the regulator. If you have no vacuum there it will cause your pressure to be high. May also be a coolant sensor telling the computer that it's a lot colder than it is, making it add additional fuel. Also look for things that would cause a reduction of air like a plugged PCV.
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From: bayside usa
THANKS FOR THE REPLYS,,,HAD PULLED THE VAC. LINE OFF THE FUEL PUMP REGULATOR TO CHECK FOR LEAKING GAS BUT DIDENT CHECK FOR VACUUM -SILLY ME- ANYWAY WILL CHECK THAT IN MORNING ALSO THINK ILL RECHECK IT FOR LEAKING FUEL THIS TIME AFTER RUNNING THE MOTOR NOT AFTER ITS BEEN SITTING FOR A WHILE...HOW WOULD I CHECK PRESSURE...PCV VALVE SEEMS TO BE WORKING -REPLACED IT 2 WEEKS AGO- AND THE HOSE IS OK..BEEN SPRAYING THE VACUUM LINES WITH CARB CLEANER AND FOUND NO LEAKS YET...THANKS MUCH
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From: peoria, az
You need a fuel pressure tester (guage) to check the pressure. It wouldn't be a bad investment to make. There is a port for testing on the fuel rail (looks like a valve stem). I don't think what you are looking for is in the form of a vacuum leak. You have either too much fuel or not enough air. If you come across a guage and check the pressure, you will want to check it with just the key on,check it with the engine running, while running, pull the vac line off the reg and note what happens, then with engine shut off watch for it to hold pressure. Incorrect readings in any of these areas could indicate a problem.
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Lead Driver
Joined: Feb 2003
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From: Oak Harbor, OH
did you replace the TPS? That is what normally causes a high idle is the TPS (throttle position sensor) sending the wrong voltage to the computer, causing the computer to "hold" the throttle open by opening the IAC,.
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From: Tennessee
To me... this sounds like a classic problem with the coolant temperature sensor.... it sends the signal to the computer telling how cold the motor is. When the motor is cold.. it sends more fuel to the motor to let it warm up.. when the temp rises, the sensor is supposed to signal for less gas. It will cause there to be black smoke from the truck and make it run rough from it getting too much gas... I would try replacing the coolant temperature sensor and see if that fixes it. It is located on the thermostat housing in the front part of the motor.. Hope this gets you back on you way.
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From: bayside usa
thanks for the replys .......stepman....think you were right..had fuel pressure checked---key on motor off no pressure, motor running at idle pressure was 40psi, race motor and pressure goes up and fluctuates between 90psi and 110psi, turn of motor no pressure..i couldent beleave how much they wanted to change the regulator..ive got to cut a alan wrench to fit in a socket to get the thing off couldent find one at the local stores..why on earth did they put this regulator so far back on motor and whats the reason its put on upsidedown..oh well.....let you all know what happens...
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From: bayside usa
so changed regulator..dont know if its me but what a pain in getting to those screws out..seems to have done the trick no more loading up,backfireing, smoke - idle is about 700 ( used to be 750rpm) - noticed a slight waver from 700 to about 600 or 650rpm dont know if i should change the tps sensor or not - already changed the iac any thoughts.....thanks again
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From: The Iron Range of Minneso
TPS change
I recieved your e-mail but was unable to respond due to the rules of the forum, I am still considered a new member. Hopefully you are are subscribed to this thread.
Yes, you have to remove the throttle body to get at the TPS.
Get a new throttle body gasket. 1. remove the air cleaner tubes.
2. remove the throttle, transmission, cruise control cables from the top of the throttle body. 3. disconnect the IAC, TBS, sensor plugs. 4. Disconnect the coolant hoses that run to the throttle body. (you can get by with only disconnecting the top one) Also remove the two vacuum hoses.
5. remove the four bolts that hold the throttle body to the upper intake. and gently pull back on it and rotate it to access the TPS it is mounted on the bottom.
6. remove the two screws holdoing the TPS to the throttle body. Note how it was mounted. Remove the TPS. ( mine was an nonadjustable type)
7. place the new senser in the same location as the old one. Tighten into place.
8. reasemble in reverse order. Torque the throttle body bolts to about 12 to 15 in pounds.
Hope this is what you are after.
Yes, you have to remove the throttle body to get at the TPS.
Get a new throttle body gasket. 1. remove the air cleaner tubes.
2. remove the throttle, transmission, cruise control cables from the top of the throttle body. 3. disconnect the IAC, TBS, sensor plugs. 4. Disconnect the coolant hoses that run to the throttle body. (you can get by with only disconnecting the top one) Also remove the two vacuum hoses.
5. remove the four bolts that hold the throttle body to the upper intake. and gently pull back on it and rotate it to access the TPS it is mounted on the bottom.
6. remove the two screws holdoing the TPS to the throttle body. Note how it was mounted. Remove the TPS. ( mine was an nonadjustable type)
7. place the new senser in the same location as the old one. Tighten into place.
8. reasemble in reverse order. Torque the throttle body bolts to about 12 to 15 in pounds.
Hope this is what you are after.
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From: bayside usa
thanks for the response....my book just says to rotate the sensor into position but not how.. anyone have a picture on what it lines up on? still dont now if i should change that tps switch ......got gone checking timing with that little thingie removed and it shows 10@ btdc so i guess its ok also went ahead and put in new spark plugs think it needed that seems to be running ok but still have to decide about changing the tps switch dont have a meter to read it on..was thinking about the iac switch that i changed - sometimes a new one part wont be up to par so...well maybe leave well enough alone.