Idle Problems Again Guys ( PLEASE HELP)
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Idle Problems Again Guys ( PLEASE HELP)
hey guys ive got a complete rebuilt 5.0 in my 1990 f150 ran fine for a weeks then it started surging at idle and going down the high every know and then it would buck like it didnt recive fuel so i cleaned throttle body and IAC and installed them back well the bucking problem and idling got better for a few weeks but no its surging again from 1000 rpms to 600rpms then back up. I went to autozone and got a new tps senor and installed and it idles a lil better but its not right and im picky. Should i change the IAC now bc ive cleaned it too many times and i when i unplug it while truck is runnign the truck dies.. PLEASE HELP
Mountain Pass
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Changing the IAC would be a good idea, but another cause of surging is a bad EGR valve. I've had that same thing happen a few times. You can try unhooking the EGR valve Vacuum line and plugging it. Your Check Engine light will come on but it won't hurt nothing. If it runs fine while unhooked, that's a instant sign that it's bad. But sometimes unhooking it won't prove it's bad if it's stuck open
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From: Calverton
hey guys ive got a complete rebuilt 5.0 in my 1990 f150 ran fine for a weeks then it started surging at idle and going down the high every know and then it would buck like it didnt recive fuel so i cleaned throttle body and IAC and installed them back well the bucking problem and idling got better for a few weeks but no its surging again from 1000 rpms to 600rpms then back up. I went to autozone and got a new tps senor and installed and it idles a lil better but its not right and im picky. Should i change the IAC now bc ive cleaned it too many times and i when i unplug it while truck is runnign the truck dies.. PLEASE HELP
A long shot, but disconnect your battery's ground for 5 minutes to rid of KAM (keep alive memory), then drive around 10 or 20 miles till computer re-adjust to the new components.
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thanks yall i will try that today after work and our local parts store had to order a IAC so hopefully it will be here soon. and when you say plug the vaccume to the egr should i do it on the top of intake?
Mountain Pass
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Do it at the EGR valve.
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i took off the egr and man was it nasty on intake and egr side so i cleaned the intake side and made a block off plate for the other side and it runs a little better but ive seemed to traced my problem to the IAC bc i can unplug it when trucks running and it will idle high then shut off so im thinking this may be the problem and i have checked all vacuum lines and fuel pressure is right where its sopposed to be.
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From: Calverton
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where should i pull vacuum from also i forgot to add it seems awful rich running that would make me think other than vacuum
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Mountain Pass
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For your vacuum, I would check it by unhooking the hose that goes too the firewall for your AC/heater controls. If you unhook that one, it won't affect any of the engine operations. You'll see where they all connect on the top middle section of your intake.
If you think it's running rich, it could be your fuel regulator. Bad fuel regulators can give those symptoms as well. Typically, that would throw a code making the check engine light come on.
If you think it's running rich, it could be your fuel regulator. Bad fuel regulators can give those symptoms as well. Typically, that would throw a code making the check engine light come on.
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thanks for the help yeah i have heat and air removed from truck, so i wont start thier but i can pull the line from any of the hoses on the intake and its pulling real hard. but i think im gunna try the regulator next after the IAC gets here. should i be able to check regulator?
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after reading up a lil on the regulator that seems to be the problem bc in the morning time after truck has been setting all night it will start right up first crank and after i drive it awhile it takes a lil bit for it start up
Mountain Pass
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In order to check the regulator you'll need a fuel pressure tester. They're kinda expensive, but sometimes you find them cheap at Harbor Freight. But I do know that Auto Zone and other places do Loan A Tool services and loan them. All you gotta do is screw it to the valve on the fuel rail of the engine. I'm not sure of the actual specs, but I've seen quite a few posts on here regarding that and these guys give GREAT info that. You WILL need the pressure test gauge, then search on this forum (or post a new topic) "Fuel pressure testing" and you'll get the info you need.It's really easy!
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thanks guys for all of your help. I changed the tps censor and didnt help to much so i changed the fuel pressure regulator and man what a difference the truck always starts on first crank now an holds steady idle and i added seafoam since my engine builder said it would be usefull in my intake to clean out the gunk an carbon truck is running great for now
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