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Discussion Starter #1
So my idle is getting worse and worse by the week. Every time i start my truck up, it idles at 900rpm as usual. After about 5-10 seconds it starts to change RPM's from 500 to 2000 rpm. up and down up and down. like i'm feathering the throttle.

I have checked all the plugs, i have spark on all cylinders, air filter is clean all electrical connections are connected. This just started about a month ago. So i changed the fuel filters twice in a month. Also have changed the oil twice, and put new plugs in.

My truck runs like a bat out of hell down the road, but idles like chit. The only problem i have mechanically with my truck is i think my oil pump is going out. I have low oil pressure...Very low. gets so bad sometimes i have to throw it in neutral at the stop lights and rev it up to keep the oil flowing. The pump is all i can think that is making it do this.

I have a 1987 F150 with the 5.0 efi. Thanks for any suggestions fellahs!:cry
 

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first of all most improtant fix your oil pump of you will be rebuliding your motor or buying a crate motor, low oil pressure with score your bearing if not spin them so after you do that its probly your IAC.An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The cars computer or ECM (electronic control module) receives information from various sensors and will output signals to adjust the IAC motor in or out to adjust engine idle speed by controlling engine idle air. An IAC motor can fail one of two ways, either the motor short circuits and stops working or the motor will develop high resistance and cause the IAC control motor to react slowly, either failure can cause the engine to stall at idle. When a trouble code scan is performed it sometimes won't always detect a failed or weak IAC motor. To check the IAC motor remove the unit, with the wires connected turn the key to the "on" position without starting the engine, the IAC should move in or out. If the IAC motor does nothing it has probably failed, replace it with a new unit and recheck system. Note: while the IAC motor is removed clean (use aerosol carburetor cleaner) the passages the IAC uses to control idle air speed, also inspect the IAC for a build-up on the seating (pointed) end and clean as necessary.
 

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Check your barometric map sensor. I had the same issues with a brand new engine. Oil pressure shpuld have been around 50psi at least and it was in the high 30s, it idoled like shit and ran hot. I was loosing my mind cause like i said brand new motor, not rebuilt, not re-conditioned, BRAND NEW!!!! then some one asked if i looked at my idol air sensor or my minifold vacuum sensor. He told me to start with the map sensor. It was 80 beansbut you know what after to short runs in the truck all my problems went away. My oil pressure is 55psi my idol is perfect and the thing is running better than it ever has just like a new motor should. The map connects to the upper plenuim and controlls pressure in the intake which basicaly with all the othersensors around there could make a real problem. my last engine was blowing a lot of oil, i think oil must have got sucked in and f it all up cause now its great. check into that not saying its it but its somewhere to start,
hope I helped out some good luck'
if Illlllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
 

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I am going to take a shot in the dark and guess you got a vaccume leak somewhere. Check where the upper intake meets the lower intake. If ya got some, use some carburator cleaner or wd 40 or starting fluid and spray it near the base where they meet. If idle levels out, compared to what it currently is, it means you've got a leak and the vacume from the motor is pulling the cleaner/fluid in...

Bad IAC valve or tps is possible...but if it runs good otherwise, I doubt that is tps. Pick up your haynes/chiltons and do the tests in the book. And pull codes. Codes may lead you straight to what your problem is...

KC
 

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Discussion Starter #7
So today i got me a can of starting fluid. I checked everywhere for vaccum leaks, i sprayed all hoses and seals and i heard nothing different. I also don't hear any leaks. All my hoses are good. I even cut out the dry rotted tubes and replaced with some new ones. I also changed the oil with some 5w-40 diesel oil. It definitely helped the low oil pressure. I can keep it on normal now, but on occasion it drops. Better than it used to be, but still unacceptable. I finally got a day off work tomorrow so i'm going to try to test the IAC and the map sensor and see where i'm at. If both are ok, i'm going to try to figure out how to pull codes. ( i have no clue where to start) :doh0715:
 

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Kitteh Commandaar!
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Well if it isn't a vacume leak, it may be a bad IAC valve. If you do the tests and they appear to be clean and good condition, here is a turtorial on pulling codes, and how to count the blinks: http://fordfuelinjection.com/?p=13 If you get codes, then go here: http://fordfuelinjection.com/?p=14 Look up your code that you got from the test...then go from there.

Good luck

KC
 

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Discussion Starter #9
I took out the IAC and used 2 full cans of brake cleaner and it fixed my probem :rockon

thanks again for the help!
 
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